PRACTICAL 1 EVALUATION OF FOOD GRAINS
FOR THEIR PHYSICAL
CHARACTERISTICS
Structure
1.1
1.2
1.3
Introduction
Quality of Grains
Sampling of Grains
1.3.1 Collection of Primary Samples
1.3.2 Preparation of the Laboratory Samples
1.4 Physical Evaluation of Food Grains
Activity 1: Physical Examination of Various Food Grains
1.1
INTRODUCTION
While selecting food products such as cereals, pulses, oilseeds etc., what are the
factors that we look for? Yes, colour, gloss, textured defects, wholesomeness etc. are
some of the factors on the basis of which we select the food products. In other terms,
we often look for good quality grains as judged by the physical appearance. For
example, the grain should not be damaged or shriveled. It should be free of any
foreign matter or it should not contain the weevilled grain etc. In this first practical,
we will introduce you to the basic concept and procedure for evaluation of food
grains for their physical characteristics. How do we collect the sample to be
analyzed? What are the sampling techniques? What are the physical characteristics
we look for while evaluating the food grains? These are a few aspects covered in this
practical.
Objectives
After studying this practical and undertaking the activity included in this practical,
you will be able to:
•
determine the various fractions involved in the physical examination of grains, and
•
detect the nonconformance of grains in terms of physical examination to the
standards.
1.2
QUALITY OF GRAINS
Food grains for human consumption are whole or broken kernels of cereals, millets
and pulses. According to PFA, they shall be free from added colouring matter. The
food grains shall not contain any insecticide residues. The food grains meant for
grinding and processing shall be clean, free from all impurities including foreign
matter (extraneous matter).
Food grains, as you may already know, are available in many processed forms but are
extensively used whole or as flours. It is much easier to clean and wash them before
cooking or grinding but if ground without cleaning they may be mixed with items of
poorer quality, drought resistant varieties which are hard to digest, not nutritious and
unhygienic. Thus, to reduce the sanitary risk (food safety) of regulated agricultural
products of plant origin intended for human consumption and use, the physical
examination is not only important but also necessary for ensuring the food quality.
Quality, you would recall reading in the theory course (MFN-008) in Unit 8, is
usually defined as a ‘degree of excellence and includes such things as taste,
appearance and nutritional content. It is the composite of characteristics – nature,
kind, status, grade of goodness, excellence etc. – that have significance and which
help in making the product acceptable’. The parameters of quality are the grades,
standards of specifications laid down by the Government or expert bodies constituted
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Principles of Food
Science
for this purpose. The most important National Standards for quality, you should
know by now, are the PFA Standards. At the International level, we have the FAO
Standards and the International Codex Alimentarius Commission, which is the
principal organ of a worldwide standard programme under the Joint Auspices of the
FAO/WHO.
In India, there are two voluntary based product certifications. Can you name them?
You have already studied about them in the Food Microbiology and Safety Course in
Unit 14. Yes, these two sets of standards are – AGMARK and Bureau of Indian
Standards Act. These are the voluntary schemes of certification aimed at providing
quality and safety of foods.
Evaluation of food grains for their physical characteristics is a scientific process, as
you would realize while reading through the next section. You will come across
various terms and procedures, which are involved in evaluation. We shall start our
study on this topic by first defining these terms and procedures.
1.3
SAMPLING OF GRAINS
The quality of the food grains is assessed starting with the process called sampling. A
sample of the product to be evaluated is taken and the physical examination
undertaken. What do we mean by the terms sample, sampling etc.? Let’s get to know
about these terminologies.
Sample means one or more units selected from a population of units, or a portion of
material selected from a larger quantity of material. A representative sample is
intended to be representative of the consignment, the bulk sample.
Sampling means the procedure used to draw and constitute a sample.
Sample size means the number of units, or quantity of material, constituting the
sample.
With a basic understanding of the terms used in the sampling of grains, we shall
move on to the sampling process. We shall begin with collection of the sample.
1.3.1 Collection of Primary Samples
Sampling of grains begins with the collection of the primary sample i.e. sample of the
consignment. The process involved in this exercise should take into consideration the
following:
1) Each primary sample should be taken from a randomly chosen position in the
consignment, as far as practically possible.
2) The primary samples should consist of sufficient material to provide the
laboratory sample(s) required.
3) The minimum number of primary samples to be taken from the consignment
shall be as indicated herewith in Table 1.1 in cases where –
Table 1.1: Collection of primary sample
Weight of the consignment
(kg)
Minimum number of primary samples
(units)* to be taken from the consignment
< 50 kg
3
50 - 500 kg
5
> 500 kg
10
(* unit can be either packages, sacks or cartons etc.)
14
Having collected the primary sample, the next step will involve preparation of
the laboratory sample. Let us see how.
1.3.2 Preparation of the Laboratory Samples
Earlier in section 1.2 we learnt that a sample is a unit, which is selected from a large
portion of material, which needs to be analyzed. From the primary sample while
selecting a representative laboratory sample, we need to consider the following:
Evaluation of Food Grains
for their Physical
Characteristics
a) Laboratory samples should be taken randomly from the bulk sample.
b) Where the bulk sample is larger than is required for a laboratory sample, it
should be divided to provide a representative portion. A sampling device, called
quartering, or other appropriate size reduction process may be used.
What is the quartering process? Let’s find out.
For carrying out the sample reduction, quartering process may be used which would
involve placing the sample on hard, clean, level surface. Divide the sample into four
approximately equal portions. Combine the two diagonally opposite portions and
weigh. Repeat the quartering process till the desired sample weight is achieved.
Figure 1.1 illustrates the quartering process.
Figure 1.1: Acceptance and rejection of diagonal portions in the quartering method
The minimum size required for laboratory samples is as given in Table 1.2.
Table 1.2: Collection of laboratory sample
Product
Examples
Nature of Primary
Samples to be Taken
Minimum Size of Each
Laboratory Sample
Packages or other whole
units, or units taken with a
sampling device
0.5 kg
Solid
products
Bread, flour,
dried fruit
Pulses
Dried beans,
dried peas
1 kg
Cereal grains
Wheat
1 kg
Oilseeds
Peanuts
0.5 kg
Note:
A smaller laboratory sample may be taken from a product of exceptionally high
value, provided that the reason(s) for doing so should be noted in the sampling
record.
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Principles of Food
Science
Let us understand this concept by taking an example of wheat flour sample. From a
given primary sample, take 500 gm of flour. Spread the whole sample into a circle on
the table and the circle (containing the flour) is divided into 4 equal parts. Discard the
2 alternate sections. Again spread the remaining 2 sections into a circle and discard 2
alternate samples. Do it 2-3 times, till the left over sample is of the desired size,
which may be 25-50 g.
Once the sample size is determined, the sample is ready for physical evaluation. Let
us get to know the process of evaluation next.
1.4
PHYSICAL EVALUATION OF FOOD GRAINS
Food grains are judged for quality by their physical, chemical and microbiological
examination. The physical examination includes checking grains for foreign matter,
organic matter, damaged grains, weeviled grains, fragments, shrivelled grains and
admixture. The various fractions as adulterants can be defined as:
1) Foreign matter means any extraneous matter other than food grains comprising of:
•
inorganic matter, consisting of metallic pieces, sand, gravel, dirt, pebbles,
stones, lumps of earth, clay and mud, animal filth and in the case of rice,
kernels or pieces of kernels, if any, having mud sticking on the surface of the
rice, and
• organic matter, consisting of husk, straws, weed seeds and other inedible
grains and also paddy in the case of rice.
2) Damaged grains means kernels or pieces of kernels that are sprouted or
internally damaged as a result of heat, microbe, moisture or weather, viz., ergot
affected grain and kernel burnt grains.
3) Discoloured grains means those grains that are discoloured to such an extent that
such discolouration materially affects the quality of the grains.
4) Weevilled grains means kernels that are partially or wholly bored by insects
injurious to grains but does not include germ eaten grains and egg spotted grains.
5) Admixture or other edible grains means any edible grains (including oil seeds)
other than the one, which is under consideration.
6) Green grains means, which are immature or green.
7) Shrivelled grains are dried and mature grains.
Grains are checked for their conformance to standards. What is a standard? Standard
is something, which is set-up and established by the authority for measuring quantity,
weight, extent value, quality. The tolerance limit of different fractions in various food
grains as given in the Prevention of Food Adulteration Act is given in Table 1.3.
Table 1.3: Tolerance limit of different fractions in various food grains
Fractions
Wheat
Jowar/ Bajra
Rice
Channa whole
Foreign matter%
by wt. (max)
1.0
1.0
1.0
1.0
Admixture%
wt.(max)
by
6.0
3.0
_
4.0
Damaged% by wt
(max)
6.0
6.0
5.0
5.0
Weevilled%
count (max)
10.0
6.0
10.0
10.0
by
*Source: 1) Prevention of Food Adulteration Act, 1954
2) Agricultural produce (Grading and Marketing) Act
Table 1.3 is used as a reference standard for physical evaluation. We shall use this
standard for physical evaluation of the food grain in the Activity presented next.
So then get started with the first activity of this manual.
16
Evaluation of Food Grains
for their Physical
Characteristics
ACTIVITY
1
PHYSICAL EXAMINATION OF VARIOUS FOOD GRAINS
Aim: To determine the quality of various food grains commonly used and grade
them accordingly.
Date: ………….
Objectives
After undertaking this activity, you will be able to:
•
•
determine the various fractions involved with the physical examination of grains,
and
check the nonconformance of grains in terms of physical examination to the
standards.
Materials Required
For conducting the activity we would require the following materials:
•
Food Grains* (list any seven food grains which you shall evaluate):
……………………………………………………………………………..
……………………………………………………………………………..
……………………………………………………………………………..
•
•
•
•
Scoop, dipper or borer to remove a unit from bulk material and from packages
Weighing machine
Clean brush for collecting the fractions
Tared butter paper or poly packs for keeping the fractions.
(* Food grains can be bajra, jowar, arhar dal, wheat grains, rice, channa whole etc.,
the minimum packing should be at least 250 g).
Methodology
Follow the following steps to carry out the activity:
1) Place the sample on a hard, clean, level surface.
2) Mix the sample thoroughly.
3) Divide the sample into four approximately equal portions.
4) Combine two diagonally opposite portions, including all fine material, and
weigh.
5) If sample does not meet the minimum required weight, then set the sample aside
and carry out the quartering process for the remaining mixture.
6) Each additional sample, using the quartering process, is to be added to the
original sample until the minimum weight is obtained.
Note: For each food product, follow the procedure listed above.
Precautions
We would like you to consider the following precautions while conducting the
practical:
1) During sampling of agricultural plant products for analytical purposes, every
precaution should be taken to prevent contamination and deterioration of the
samples or subjecting the samples to such changes that the residue content
thereof is affected.
2) Weighing should be carried out accurately.
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Principles of Food
Science
3) The collection of the fractions should be done with a clean brush and not with
fingers.
4) The fractions should be properly categorized.
Findings
Put down your findings, for each of the food grain examined, in the tabular form
under the different heads in the format given on page 19.
After picking, weigh the sample and the different fractions from the original sample
to find % of each in the sample. Put down the findings in the last two columns.
Inference
Sum up your findings for each food grain examined here in the space provided.
Food grains
1) ……………………………………………………………………………...
2) ……………………………………………………………………………...
3) ……………………………………………………………………………...
4) ……………………………………………………………………………...
5) ……………………………………………………………………………...
6) ……………………………………………………………………………...
7) ……………………………………………………………………………...
Conclusion: (In this section, present a summary of your findings. Comment which
sample had the best or bad quality, had maximum adulteration etc.)
…………………………………………………………………………………..
…………………………………………………………………………………..
…………………………………………………………………………………..
…………………………………………………………………………………..
…………………………………………………………………………………..
Submit the activity for evaluation.
………………………………
Counsellor Signature
18
PRACTICAL 2
HONEY
Structure
2.1 Introduction
2.2 Honey –The Simple Sugar
2.3 Honey – Characteristics, Specifications and Requirements
2.4 Physical Criteria for Quality
2.5 Marking
Activity 1: Determination of Total Reducing Sugar
Activity 2: Determination of Sucrose Content
Activity 3: Detection of Adulteration
Activity 4: Determination of Fructose to Glucose Ratio
Activity 5: Determination of Acidity
2.1
INTRODUCTION
The first Unit in the theory course (MFN-008) focused on simple sugars. In the unit,
you may recall studying that foods made from sugar, as well as, corn syrup, honey
and molasses are simple carbohydrates. The second practical in this manual focuses
on the study of honey, which is a simple sugar. Honey comes under the purview of
Prevention of Food Adulteration Act (PFA). We shall learn about the characteristics
of honey and the physical criteria for quality of honey. This practical will help you
check the conformance of any sample of honey to the standards.
Objectives
After studying this practical and undertaking the activities included in this practical,
you will be able to:
•
•
•
•
•
2.2
enlist the honey characteristics which are basic for a good quality honey,
estimate the reducing and non-reducing sugars present in honey,
determine the fructose to glucose ratio in honey,
detect adulteration of honey with commercial sugars, and
check the conformance of a honey sample to the standard.
HONEY – THE SIMPLE SUGAR
Honey is the oldest sweet food known to man. Although honey is a natural
sweetener, it is considered a refined sugar because 96% of dry matter is simple
sugars: fructose, glucose and sucrose. Honey has the highest calorie content of all
sugars with 65 calories/tablespoon, compared to the 48 calories/tablespoon found in
table sugar.
Honey is produced by honey bees from nectar of plants, as well as, from honey dew.
Among the components of honey (sugars, water, organic acids, enzymes, amino
acids, wax, pigments and pollen etc.), some of the components are derived from
plants, some are added by the bees and some are due to maturation of honey.
The honey marketed in India falls under two categories:
1) Extracted Apiary Honey
2) Squeezed Honey
Bulk of squeezed honey is obtained from Apis Dorsata, the rock bee, and bulk of the
extracted honey is obtained by Apis Serana Indica (Honey bee).
We shall get to know about the basic characteristics, specifications and requirements
of honey next.
20
2.3
Honey
HONEY – CHARACTERISTICS, SPECIFICATIONS
AND REQUIREMENTS
Honey comes under the purview of Prevention of Food Adulteration Act (PFA). This
Indian Standard was adopted by ISI on 30th September, 1974 after the draft finalized
by the Apiary Industry Sectional Committee had been approved by the Agricultural
and Food Product Division Council (AFPDC).
Due to its limited production and high cost, honey is prone to adulteration by cane
sugar, invert syrup and high fructose glucose syrup. While preparing this
specification, the committee recognized the need to market squeezed and apiary
honey separately so that there can be growth of consumer demand of apiary honey,
which is reared scientifically and processed hygienically. The present revision of the
standard incorporates a number of modifications, which include:
a)
b)
c)
d)
The scope of the standard has been restricted to extracted honey.
Limit of total reducing sugar has been increased for standard grade.
Limit of sucrose content has been reduced for A grades and standard grades.
Method of glucose fructose ratio content has been modified to make it more
precise.
So far, no separate standard has been issued on squeezed honey. While compiling the
revision, the Apiary Industry Sectional Committee (AISC) felt that squeezed honey
collected from jungles is being sold at a much lower price, further it was possible to
distinguish it from apiary honey which has much less number of pollens. The Central
Bee Keeping Research Institute is conducting investigation on the method of
quantitative estimation for pollens and its limits in Apiary and squeezed honey.
Subsequently, a separate standard would be issued and has been issued on squeezed
honey, while framing these specification consideration have been given to the
prevailing trade practices and the different grades prescribed by the Agricultural
marketing Advisor to the Government of India for incorporation of Agmark rules
framed under the Agricultural procedure for grading and marketing. This standard is
also subject to the restriction imposed under the Prevention of Food Adulteration Act
1954 and rules framed there under whenever applicable.
This standard prescribes the requirements and methods of sampling and testing for
extracted in Apiary honey obtained from Apis Serana indica. Honey shall be of the
following grades:
a) Special
b) Grade A
c) Standard
Table 2.1 gives the characteristics and specifications for honey.
Table 2.1: Characteristics and specifications of honey
S.No
1.
2.
3.
4.
5.
6.
7.
8.
9
Characteristics
Grade
Specific gravity at 27º C minimum
Moisture % by mass (maximum)
Total reducing sugar % by mass
(minimum)
Sucrose % by mass (maximum)
Fructose – glucose ratio (minimum)
Ash % by mass (maximum)
Acidity expressed as formic acid, %
by mass (maximum)
Fiehe’s Test
Aniline chloride Test
ISI-4941, 1974
PFA Act,
rule
A07.03d
Special
1.41
20
70
A
1.39
22
65
Standard
1.37
25
65
25
65
5.0
1.0
0.5
0.2
5.0
1.0
0.5
0.2
5.0
1.0
0.5
0.2
5.0
0.9
0.5
-
-ve
-ve
-ve
-ve
-ve
-ve
-ve
-
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Principles of Food
Science
According to PFA Act, 1954 and the rules in 1955, honey has been defined as the
food derived entirely from the work of bees operating upon the nectar of flowers and
other sweet exudation of plants. IS specifications have been laid down as given
herewith to prescribe the requirements of honey, which are as follows:
A) General Characteristics
1) It should be a well-ripened natural product.
2) It should be clear and visually transparent.
3) It should be extracted with the help of an extractor.
4) It should free from objectionable flavour due to over heating, fermentation
and smoke.
5) It should have been strained clean through double thickness of cheese cloth
about 150 µ at a temperature not exceeding 70º C.
6) Freedom from foreign matter: When visually inspected honey shall be free
from foreign matter such as dirt, mould, scum, piece of beeswax, fragments
of bees and other insects and from any other extraneous matter.
7) Colour: Colour of honey shall be uniform throughout and may vary from
light to dark brown.
8) Packaging and Marketing: Honey shall be packed in hygienically clean wide
mouthed glass containers, or in acid-resistant lacquered tin containers or in
suitable polyethylene containers. The screwed saps of glass containers shall
be non-corrosive and non-reacting material to honey and shall be provided
with cork washes to avoid spilling.
Having studied about the characteristics, specifications and requirements, let us next
look at the physical criteria for quality of honey.
2.4
PHYSICAL CRITERIA FOR QUALITY
Colour, crystallization, pH, acidity, water content are some of the criteria used for
analysis of honey. These criteria are described next.
A) Colour
The colour of the honey varies from straw-yellow to nearly black according to its
botanical source and to conditions of processing and storage it has undergone. Light
coloured honey typically has a mild flavour, while dark coloured honey is usually
stronger in flavour. Blended honey is normally graded by colour, the lighter the
colour, the higher the quality and value.
B) Crystallization
At normal temperatures honey exists as clear syrup preferred by consumers.
However, on storage, coarse granulation or crystallization can occur, which is a
natural process that occurs in honey. Honey is a supersaturated sugar solution out of
which the glucose tends to crystallize. The tendency of honey to granulate depends
on glucose/water ratio. At a ratio of 2:1, it granulates rapidly, whereas, honeys
with ratio of 1.7:1 or less tend to remain liquid. Crystallization is most rapid at
14º C (57º F) and can be revered by heating.
C) Sugars
22
The major sugars present in honey are fructose, glucose, followed by lower
concentration of sucrose and maltose. The actual proportion of glucose to fructose in
any particular honey depends largely on the source of the nectar. The average ratio of
fructose to glucose is 1.1:1. Other sugars found in small amounts in honey are
isomaltose, nigerose, kojibiose, turanose, gentibiose and laminaribose.
To assess the quality of honey, total reducing sugars and sucrose content is most
commonly determined. Lane and Eynon method is used for determination of sugars.
The total reducing sugars are estimated by titration using Fehling A and B solutions,
whereas, sucrose is determined indirectly by calculating difference in total reducing
sugar before and after inversion of sugars in honey. Invert sugar reduces the copper
in Fehling’s solution to red, insoluble cuprous oxide. The sugar content of the food
sample is estimated by determining the volume of the unknown sugar solution
required to completely reduce a measured volume of Fehling’s solution. However,
more recently this method is replaced by measurement of specific sugars by high
performance liquid chromatography equipped with refractive index director. As per
the Indian standards, honey should not contain reducing sugars less than 65% and
sucrose more than 5%. Value of sucrose higher than this indicates bees might be fed
artificially with sugar or direct addition of sugar, to earn more profits. Its is
interesting to note that enzymes present in honey cause changes in the proportions of
the original sugars present and the sucrose may disappear completely during
prolonged storage.
Honey
The principle behind the Lane and Eynon method is discussed next.
Lane and Eynon method: Principle
Reducing sugars are those, which have free sugar groups (e.g. glucose, fructose etc.)
and hence may be estimated directly by titrating the solution of the sample with
Fehling’s solution. You may recall reading about this property of sugars in unit 1 in
the Nutritional Biochemistry Thoery Course (MFN-002). Total sugars include both
reducing and non-reducing sugars. Non-reducing sugars (e.g. maltose, lactose,
sucrose etc.) do not contain free sugar groups and cannot reduce Fehling solution.
Hence, non-reducing sugars must be hydrolyzed to monosaccharides by heating with
acid before titration.
Reducing sugars are acted upon by the alkali of the Fehling solution to form enediols.
These enediols are very unstable and reactive and they reduce Cu²+ ions to Cu+ ions.
These Cu+ ions combine with hydroxyl groups to form cuprous hydroxide, which on
heating gives red precipitate of cuprous oxide. To get a sharp end point, methylene
blue is added which is reduced to a colourless leuco compound restoring the red
colour of the solution. Sodium potassium tartarate keeps the Cu²+ ions in the solution,
thus ensuring a continuous supply of Cu²+ ions for reduction.
Reactions involved in the estimation of Reducing sugars and Non-Reducing sugars
are illustrated next.
Reaction for Reducing Sugars
23
Principles of Food
Science
Reaction for Non-Reducing Sugars
D) Total Solids and Water
Most genuine honeys contain 13-23 per cent of water. The total solids or moisture
can be estimated by drying in a vacuum oven at 70ºC. Alternatively, it can also be
determined by measuring refractive index at 40ºC or by measuring the specific
gravity of 20% (m/v) solution of honey. Tables relating the refractive index of honey
with water content are available in literature.
E) Ash
Standards allow ash content in honey up to 0.5 per cent, but the ash of genuine honey
seldom exceeds 0.35 per cent. It is determined by charring, preferably under an infrared lamp followed by ashing at 600ºC and very recently, this measurement is
replaced by measurement of electric conductivity. This measurement depends on the
ash and acid content of honey – the higher their content, the higher the resulting
conductivity. Extensive conductivity data published on thousands of commercial
honeys suggest that blossom honeys, mixtures of blossom and honey dew honeys
should have conductivity less than 0.8 milli Siemens/cm.
F)
pH and Acidity
The pH of natural honey ranges from 3.4 to 6.1. Acidity of honey is primarily due to
presence of acids such as gluconic acid, pyruvic acid, malic acid, citric acid and
succinic acid. Acidity of fresh honey is usually very low, 13 to 35 mEq/kg. Honey
with acidity more than 40 mEq/kg is considered as poor in quality. Acidity is
determined by titration of a known weight of honey with 0.1M NaOH.
Finally, let us look at the marking regulations for honey.
2.5
MARKING
The marking regulations indicate that each container of honey shall be suitably
marked so as to give suitable information as follows:
24
a) Name of the material and grade designation
Honey
b) Name of the packer
c) Batch or code no.
d) Net weight
Honey is the nectar of flowers that is collected, modified and concentrated by honey
bee. It contains 75 % glucose and fructose and 2% or more sucrose. As defined by the
Food and Drug Administration, honey may not contain more than 8% sucrose - a
higher % is taken as an indication of adulteration by added sucrose. Honey is one
material food product, which contains more fructose than glucose. The relative
amounts being 40.5% of fructose and 34.5% of glucose.
Flavours of honey differ according to the characteristics esters present in the nectar of
different flowers. Honeys also come from orange and other citrus blossom, wild sage,
cultivated buckwheat and tulip tree. The colour of honey may vary from white to
amber or darker graded or qualities of honey are independent of colour but darker
coloured honey generally has a stronger flavour than the light coloured ones. It is also
more acid, which has some significance in the use of soda to neutralize the acidity of
honey used as a partial substitute for sugar in flavour mixture.
A process has been developed for producing dried honey. The product has colour and
flavour quite close to that of original honey. It has granular form, is free flowing and
has a longer shelf life. It may have sucrose added for the purpose of raising the
temperature at which the dried product will soften thus making it more resistant to
caking at high temperature.
With the basic understanding about the characteristics, specifications, requirements
and criteria of quality for honey, let us now carry out the activities 1-5 given
herewith.
25
Principles of Food
Science
ACTIVITY
1
Date: ………….
DETERMINATION OF TOTAL REDUCING SUGAR
Aim: To determine total reducing sugars in the given sample of honey.
Objectives
This activity will help you to:
•
estimate reducing sugars in a sample of honey,
•
check the conformance or non-conformance of the samples to the standards, and
•
detect adulteration of honey with commercial sugars.
Principle
Now, write the principle regarding the estimation of reducing sugars by Lane and
Eynon method as studied in section 2.4 above.
Reaction Involved
(Write the reaction given by reducing sugar in the space provided).
26
Reagents Required
Honey
1) Standard invert sugar solution: Weigh accurately 0.985 g of sucrose and dissolve
in 500 ml of water. Add 2 ml of concentrated H2SO4. Boil gently for 30 minutes
and keep aside for 24 hours. Neutralize this with Na2CO3 and make the final
volume to 1000 ml. 30 ml of this solution contains 0.05 g of invert sugar.
2) Fehling A and Fehling B
3) Methylene blue indicator.
Materials Required
Sample of honey
Burette
Pipette
Conical flask
Beaker
Distilled water
Procedure
You will be carrying out the procedure in two steps using Lane Eynon Method.
Step 1
It involves the standardization of copper sulphate solution. The procedure for this
standardization can be conducted in the underlined manner as:
1) Pipette accurately 5 ml of Solution A and Solution B in conical flask of 250 ml
capacity.
2) Heat this mixture to boiling on an asbestos gauge and add standard invert sugar
solution from the burette about 1ml less than the expected volume which will
reduce the Fehling solution of say, 48 ml.
3) Add 1 ml methylene blue indicator.
4) Carry out the titration and complete it within 3 minutes.
5) The change in blue to reddish brown colour due to cuprous oxide formation is
taken as the end point.
6) From the volume of the invert sugar solution used, the strength of CuSO4 is
calculated by multiplying the titrated value with 0.001 (mg/ml of the standard
invert sugar solution). This is known as Fehling factor.
Note:
Carry out the titration till you get consecutive titre value. This means you
may have to repeat the titration 3-4 times till you get the same result.
Step 2
It involves the titration of the sample honey solution wherein the steps can be
followed as given below:
1) Place accurately 1 gm of honey solution in 250 ml of volumetric flask.
2) Dilute with about 150 ml of water.
3) Mix thoroughly contents of glass and make the volume to 250 ml.
4) In another conical flask, add 5 ml of Fehling A + 5 ml of Fehling B.
5) Heat to boiling with 20 ml of water.
6) From burette add honey solution (approx 40 ml) and boil.
7) Add methylene blue indicator do the titration within 3 minutes.
8) Carry out the titration till blue colour changes to red.
9) Now calculate the reducing sugar using the calculation given next.
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Calculations:
250 ×100 × S
H×M
Reducing sugar =
where,
S = Fehling’s factor (as obtained from standardization procedure of CuSO4
undertaken in step 1 of the procedure earlier). Strength of CuSO4 solution / Fehling
factor (S) is calculated as:
Titre value of standard invert sugar solution × 0.001
H = Volume of honey solution required (burette reading)
M = Mass of honey
Precautions
1) Each titration should be completed within three minutes.
2) Maintain continuous evolution of steam to prevent reoxidation of Cu²+ ions.
Results and Observations
Record your observations in the format below according to the procedure you
followed in step 1.
Standard invert sugar solution
Burette reading (ml)
S. No.
Initial
Final
Difference
Pilot
1
2
3
Titre value = ………………….
Strength of CuSO4 solution / Fehling factor (S) is:
Titre value × 0.001= ……………………..
Solution of Honey
Record your observations in the format below according to the procedure you
followed in step 1.
Burette reading (ml)
S. No.
Initial
Final
Difference
Pilot
1
2
3
Titre value = ……………………..
28
H (volume of honey solution required) = …………….. ml
Honey
M (mass of honey taken for preparation of the solution) = ……………g
Putting the values in the formula, we get
Reducing sugar =
250 ×100 × S
H×M
Inference and Conclusion
Total reducing sugar in given honey sample (% by mass) was found to be
………………………………………
The given sample of honey according to BIS falls under ……………grade*.
* (Look up the specifications given in Table 2.1 for comparison).
Submit the activity for evaluation.
………………………………
Counsellor Signature
29
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ACTIVITY
2
DETERMINATION OF SUCROSE CONTENT
Date: ………….
Aim: To determine the sucrose content in the given sample of honey.
Objectives
This activity will help you to:
•
•
•
estimate the non-reducing sugars and total sugars in a sample of honey,
check the conformance or non-conformance of the samples to the standards, and
detect adulteration of honey with commercial sugars.
Principle
Write down the principle in the space provided herewith. You have already studied
the principle in section 2.4.
Reaction Involved
(Write the reaction of non-reducing sugars in the space provided)
30
Reagents Required
Honey
1) Standard invert sugar solution: Weigh accurately 0.985 g of sucrose and dissolve
in 500 ml of water. Add 2 ml of conc. H2SO4. Boil gently for 30 minutes and
keep aside for 24 hours. Neutralize this with Na2CO3 and make the final volume
to 1000 ml. 30 ml of this solution contains 0.05 g of invert sugar.
2) Fehling A and Fehling B
3) Methylene blue indicator.
4) 0.4 N HCl
5) 0.6 N NaOH
Materials Required
Burette
Pipette
Conical flask
Beaker
Distilled water
Procedure
The procedure (method of estimation is Lane Eynon method as studied in section 2.4)
involving the estimation of non-reducing sugars will be carried out in 3 steps.
Step 1: Acid Hydrolysis of Non-Reducing Sugar
It involves the acid hydrolysis of non-reducing sugars to reducing sugars. It is also
known as the process of inversion. Acid hydrolysis results in breakdown of sucrose
into glucose and fructose. The process of inversion can be carried out in the
following manner:
1) Place accurately 1 gm of honey solution in 250 ml of volumetric flask.
2) Dilute with about 150 ml of water.
3) Mix thoroughly contents of glass and make the volume to 250 ml.
4) Take 100 ml of this solution and add 6 ml of 0.04 N HCl.
5) Heat the solution to boiling.
6) Keep for ½ an hour.
7) Neutralize this inverted honey solution with 0.6N NaOH.
Step 2: Standardization of Copper Sulphate Solution
It involves the standardization of copper sulphate solution. This is same as done in
the previous activity.
1) Pipette accurately 5 ml of Solution A and Solution B in conical flask of 250 ml
capacity.
2) Heat this mixture to boiling on an asbestos gauge and add standard invert sugar
solution from the burette about 1 ml less than the expected volume which will
reduce the Fehling solution of say, 48 ml.
3) Add 1 ml methylene blue indicator.
4) Carry out the titration and complete it within 3 minutes.
5) The change in blue to reddish brown colour due to cuprous oxide formation is
taken as the end point.
6) From the volume of the invert sugar solution used, the strength of CuSO4 is
calculated by multiplying the titrated value with 0.001 (mg / ml of the standard
invert sugar solution). This is known as Fehling factor.
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Note: carry out the titration till you get consecutive titre value. This means you may
have to repeat the titration 3-4 times till you get the same result.
Step 3: Titration of inverted honey solution
It involves the titration of the inverted honey solution (sample obtained after carrying
out step 1). Carry out the titration in the following manner.
1)
2)
3)
4)
5)
In a conical flask take 5 ml of Fehling A+5 ml of Fehling B.
From burette add the inverted honey solution (approx 10 ml) and boil.
Add methylene blue indicator do the titration within 3 minutes.
Carry out the titration till blue colour changes to red.
Calculate total sugar using the formula given next.
Calculations
Total sugars =
250 ×100 × S
H×M
where,
S = Fehling’s factor (as obtained from standardization procedure of CuSO4
undertaken in step 2 of the procedure earlier). Fehling factor (S) is calculated as:
Titre value of standard invert sugar solution × 0.001
H = Volume of inverted honey solution required (burette reading)
M = Mass of honey
Sucrose (% by mass) = (Total sugars – reducing sugar) × sucrose factor
where, sucrose factor is 0.95 and reducing sugar value is taken as calculated in
Activity 1.
Precautions
1) Each titration should be completed within three minutes
2) Maintain continuous evolution of steam to prevent reoxidation of Cu2+ ions.
Results and Observations
Record your observations in the format below according to the procedure you
followed in step 2 above.
Standard invert sugar solution
Burette reading (ml)
S. No.
Initial
Final
Difference
Pilot
1
2
3
Titre value = ……………………….
Strength of CuSO4 solution / Fehling factor (S) is
Titre value …………… × 0.001= …………………
Solution of Honey (inverted)
32
Record your observations in the format below according to the procedure you
followed in step 3.
Burette reading (ml)
S. No.
Initial
Honey
Final
Difference
Pilot
1
2
3
Honey solution required = …………………
H (volume of honey solution required) = ………………... ml
M (mass of honey taken for preparation of the solution) = ……….……………. g
Putting the values in the formula, we get
Total sugars =
250 ×100 × S
H×M
Sucrose (% by mass) = (Total sugars – reducing sugar) × sucrose factor
where, sucrose factor is 0.95 and take reducing sugar value as calculated in
Activity 1.
Sucrose (% by mass) for the given honey sample is ……………….. .
Inference
Total reducing sugar in given honey sample (% by mass) was found to be ………..
Total sugars in the given sample of honey was found to be ………………… .
Sucrose percentage by mass was found to be ………………….. .
The given sample of honey conforms / does not conform to the specification laid
down and falls under …………………. grade.
Submit the activity for evaluation.
…………………………
Counsellor Signature
33
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Science
ACTIVITY
3
DETECTION OF ADULTERATION
Date: ………….
Aim: To determine the adulteration in the given honey sample by Fiehe’s test and
Aniline chloride test.
Objectives
This activity will help you to:
•
•
check the given samples of honey for any adulteration with commercial sugars,
and
check the conformance or non-conformance of the samples to the standards.
Principle
The major quality factor in honey is the indicator of honey freshness and overheating.
Hydroxy Methyl Furfural (HMF) occurs in honey due to acid-catalyzed dehydration
of hexose sugars. Its value in natural fresh honey varies from 10 to 14 mg/ kg, but it
increases upon storage, depending on the pH of honey and on the storage
temperature.
HMF content of honey also increases upon its adulteration by invert sugars. Presence
of invert sugar in honey is assessed by Fiehe’s test where HMF reacts with resorcinol
and gives a red coloured complex. According to PFA Act, Fiehe’s test should be
negative for honey, whereas Codex Standards states that HMF content of honey
should not be more than 60 mg/kg.
Materials Required
1)
2)
3)
4)
5)
6)
Sample of honey
Resorcinol solution
Ether
Aniline chloride solution
Pestle and Mortar
Beakers
Procedure
The procedure for Fiehe’s test and Aniline chloride is given herewith. Carry out these
test following the steps enumerated herewith.
Fiehe’s test
1) Take 5 g of honey in pestle and mortar.
2) Mix honey solution with 10 ml ether (you will notice that honey or ether will not
mix).
3) Now, decant ether extract into porcelain dish.
4) Repeat this extraction twice. Allow the extract to evaporate to dryness at room
temperature.
5) Add a large drop of resorcinol solution into the porcelain dish with the residue.
6) The production of cherry red colour indicates a positive reaction.
If the Fiehe’s test is positive, we go for Aniline chloride test for conformation of
adulteration (i.e., presence of commercial sugar).
Aniline chloride test
1) Take 5 gm of honey in a porcelain dish.
2) Add 2.5 ml of prepared aniline chloride solution to it and keep stirring.
34
3) In the presence of commercial invert sugar the presence of orange red colour to
fuming red within 1 minute indicates a positive test.
Honey
Observations
(Write your observations about both the tests in the table provided herewith).
S.No.
Test
Colour
1.
Fiehe’s test
2.
Aniline chloride test
Observation
Positive/ Negative
Result
The given sample of honey was found to be (pure/impure) and …………..
(unadulterated/adulterated) as Fiehe's and Anniline chloride tests were ………
(negative/positive).
Submit the activity for evaluation.
………………………..
Counsellor Signature
35
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Science
ACTIVITY
4
DETERMINATION OF FRUCTOSE TO GLUCOSE RATIO
Date: ………….
Aim: To determine the fructose to glucose ratio in honey.
Objectives
This activity will help you to:
•
check the given samples of honey for any adulteration with commercial sugars,
and
•
check the conformance or non-conformance of the samples to the standards for
fructose to glucose ratio
Principle
The major sugars present in honey are fructose, glucose, followed by lower
concentration of sucrose and maltose. The actual proportion of glucose to fructose in
any particular honey depends largely on the source of the nectar. The average ratio of
fructose to glucose is 1.1:1. Other sugars found in small amounts in honey are
isomaltose, nigerose, kojibiose, turanose, gentibiose and laminaribose. Although,
analysis of honey for physical, chemical and microbiological parameters give a good
picture about the quality of honey, but, it is possible that the adulteration with the low
cost sugar syrups such as invert syrups or high fructose corn syrup (HFCS) may go
undetected. Thus, now-a-days carbon isotope ratio methods are recommended by
Association of Official Analytical Chemists (AOAC) to detect the adulteration of
expensive honey with cheap HFCS and invert cane sugar. According to this method,
the carbon isotope ratio of the honey and that of the protein isolated for that honey
should be similar, as nearly all the protein in honey originates from the bee in the
form of enzymes that ripen the nectar. The addition of corn syrup to honey will
change the carbon isotope ratio of the honey but not of the protein. If the honey has
been adulterated with invert sugar or HFCS, the honey will have ratio of the carbon
isotope significantly different from that of honey protein.
But, here in this exercise we will be carrying out the simple experiment on detection
of fructose to glucose ratio titration.
Reagents Required
Iodine (I2) solution (0.05 N)
NaOH - 0.1 N
Standard sodium thio sulphate solution = 0.05 N = 12.4 g/l
Starch solution (freshly prepared)
Materials Required
Sample of honey
Iodination flask
Beaker
Burette
Procedure
Carry out the activity following the steps enumerated herewith.
1) Place accurately 1 gm of honey solution in 250 ml of volumetric flask.
2) Dilute with about 150 ml of water.
3) Mix thoroughly contents of glass and make the volume to 250 ml.
4) Pipette 50 ml of honey solution in a 250 ml stoppered iodination flask.
5) Add 40 ml of Iodine solution.
36
6) Add 25 ml of NaOH solution.
Honey
7) Stopper the flask and keep in dark place for 20 minutes.
8) Acidify the solution with 5 ml of H2SO4 and titrate quickly the excess of I2
against standard Sodium thiosulphate solution.
9) After adding some sodium thiosulphate add few drops of starch solution and see
the change of colour from voilet to colourless.
10) Now repeat steps 5 to 9 once again. Start by taking 50 ml water (distilled) instead
of honey solution. This is your blank sample.
11) Calculate the fructose glucose ratio with the help of following calculations:
Calculations
A) Approximate glucose % by mass (W) =
(B − S) × 0.004 × 100 × 5
a
where, B = volume of sodium (Na) thiosulphate used for blank
S = volume of Na thiosulphate used for sample
a = mass of honey taken for the test
B) Approximate fructose % by mass (X) =
Approximate total reducing sugar (% after inversion) – w
0.925
Here total reducing sugar (% after inversion) value can be taken as calculated in
Activity 2 earlier.
C) True glucose % by mass (Y) = W – 0.012 X
D) True fructose % by mass (Z) =
Approximate reducing sugar beforeinversion(%) − Y
0.925
Here approximate reducing sugar before inversion value can be taken as
calculated in Activity 1.
E) Total reducing sugar % by mass = Y + Z
F) Fructose to glucose ratio =
True fructose % by mass (Z)
True Glu cos e % by mass (Y)
Results and Observations
Record your observations in the format given below:
Volume of Na thiosulphate used for blank (B) = ………….. ml
Volume of Na thiosulphate used for sample (S) = …………. ml
Mass of honey taken for analysis (a) = ………….. g
Now calculate the following:
A) Approximate glucose % by mass (W) =
(B − S) × 0.004 × 100 × 5
a
Putting in the values, we get:
Approximate glucose % by mass (W) = …………………
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B) Total reducing sugars after inversion were found to be (% by mass) = ……
Write down the value of total sugar (inverted) obtained in Activity 2 of this
practical from page 33.
C) Total reducing sugars before inversion were found to be (% by mass) = …..
Write the value of total reducing sugar obtained in Activity 1 of this practical
from page 29
D) Approximate fructose % by mass (X) =
Approximate total reducing sugar (% after inversion) – w
0.925
Putting in the values we get
E) True glucose % by mass (Y) = W – 0.012 X
(Putting the values we get):
F) True fructose % by mass (Z) =
Approximate reducing sugar beforeinversion(%) − Y
0.925
(Putting the values we get):
G) Fructose to glucose ratio =
(Putting the values we get):
38
True fructose % by mass (Z)
True Glu cos e % by mass (Y)
Inference
Honey
The sample of honey analyzed gave …………. fructose to glucose ratio. According
to the specifications laid down the fructose to glucose ratio should be ………….
Thus, the sample of honey was found to be conforming/non conforming to the
standards.
Submit the activity for evaluation
………………………….
Counsellor Signature
39
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Science
ACTIVITY
5
DETERMINATION OF ACIDITY
Date: ………….
Aim: To determine the acidity in the given sample of honey.
Objectives
This activity will help you to:
• carry out the acidity test of the given samples of honey,
• learn about the keeping quality of honey, and
• check the conformance or non-conformance of the samples to the standards for
acidity.
Principle
The pH of natural honey ranges from 3.4 to 6.1. Acidity of honey is primarily due to
presence of acids such as formic acid, gluconic acid, pyruvic acid, malic acid, citric
acid and succinic acid. Acidity of a afresh honey is usually very low, 13 to 35
mEq/kg. Honey with acidity more than 40 mEq/kg is considered as poor in quality.
Acidity is determined by titration of a known weight of honey with 0.1M Sodium
hydroxide (NaOH).
Materials Required
0.1 N NaOH
Phenolphthalein indicator
Conical flask
Pipette
CO2 free water
Procedure
Now carry out the activity following the steps enumerated herewith:
1) Take 10 g of honey sample in a ‘conical flask’.
2) Dissolve in it 75 ml of CO2 free water (Boiling distilled water and cooling).
3) Mix thoroughly and titrate against standardized NaOH using phenolphthalein as
indicator. (Add 1 ml of phenolphthalein during mixing of honey and water).
4) Observe for the change in colour to light pink.
5) Pink colour should persist for at least 10 seconds.
6) Also conduct blank titration with 85 ml of CO2 free water and phenolphthalein
indicator.
7) Calculate the acidity using the formula given herewith:
Calculations
Acidity is expressed as % formic acid by mass in honey.
Equivalent weight of formic acid = 0.23
Acidity =
0.23 × Volume of NaOH
Mass of Honey
 Volume of
  Volume of




Volume of NaOH =  NaOH required  −  NaOH required 
 for sample titration   for blank titration 
40
Results and Observations
Honey
Record your observations as indicated
Mass of honey taken for analysis = ……………… g
Volume of NaOH used = ………………. ml
Acidity =
0.23 × titre volume
Mass
Putting in the values we get,
Acidity (% by mass) as ………………….
Inference
Acidity (% by mass) of the given sample was calculated as ……………… .
According to the specifications the acidity of honey should not exceed by …………..
% by mass.
Thus, the given sample of honey was found to be (conforming/non-conforming) to
the standards.
Submit the activity for evaluation.
……………………….
Counsellor Signature
41
PRACTICAL 3 EXPERIMENTS ON THE
CHEMISTRY OF CEREALS
Structure
3.1
3.2
3.3
Introduction
Cereals – Basic Introduction
Characteristics of Various Flours
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
Moisture Content
Ash Content
Gluten Content
Crude and Dietary Fibre
Alcoholic Acidity
Activity 1: Determination of the Moisture Content
Activity 2: Determination of the Total Ash Content
Activity 3: Determination of the Acid Insoluble Ash
Activity 4: Determination of the Crude Fibre Content in the Given Sample of Flour
Activity 5: Determination of the Gluten Content
Activity 6: Determination of the Alcoholic Acidity of the Given Sample of Flour
3.1
INTRODUCTION
The third practical in this manual focuses on experiments specific to the chemistry of
cereals. We have already studied about the chemistry of cereals in the theory booklet
in Unit 2. Here, we shall learn about the various characteristics/parameters specific to
cereals and their processed products refined flour (maida), semolina (suji), whole
wheat flour (atta), whole meal barley flour etc. and the experiments/tests involved in
the analysis of these parameters.
Objectives
After conducting the various activities included in this practical, you will be able to:
•
enumerate the various characteristics/parameters specific to cereals and cereal
products,
•
assess the moisture content in any given sample of flour,
•
determine the ash content in any given sample of flour,
•
analyze the acid insoluble ash in any given sample of flour,
•
assess the crude fibre content in any given sample of flour,
•
demonstrate the procedure for determination of undigestible residue for dry
samples,
•
determine the gluten content and water absorption power of any given sample of
flour,
•
check the acidity of any given sample of flour, and
•
check any given sample for conformance to the standards.
3.2
42
CEREALS – BASIC INTRODUCTION
The word “cereal” is derived from the name of the Roman grain or harvest goddess,
Ceres. Cereals are the seeds of the grass family. These are the complex carbohydrates
and consist of complex mixture of molecules of different sizes and structures. Starch
is the major component but varies in structure in different grains. Cereals are the
energy providers and constitute a high percentage of calorie and protein intakes of
man. They form an important staple food in most developing countries. The major
cereals are wheat and rice. Cereals are mostly consumed in the processed form. The
processing operations involve the processes as sprouting, malting, puffing,
milling/grinding, flaking and extruding. Cereals are covered under PFA rules, 1955
(Appendix B, Rule 5) and are described as:
Experiments on the
Chemistry of Cereals
A.18.01.---ATTA OR RESULTANT ATTA means the coarse product obtained by
milling or grinding clean wheat free from rodent hair and excreta.
A.18.02. ---MAIDA means the fine product made by milling or grinding clean wheat
free from rodent hair and excreta and bolting or dressing the resulting wheat meal.
A.18.01.01---FORTIFIED ATTA means the product obtained by adding one or
more nutrients to atta.
A.18.01.02---PROTEIN RICH (PAUSHTIK) ATTA means the product obtained by
mixing wheat atta with groundnut flour or soya flour or a combination of both.
A.18.05.---PEARL BARLEY or BARLEY (JAU) shall be the product obtained from
sound and clean barley (Hordeum vulgare or Hordeum distichon). It shall be whitish
in colour and shall be free from fermented, musty or other objectionable taste or
odour, adulterants and insect and fungus infestation and rodent contamination. It shall
not contain other food grains more than 1 per cent by weight to an extent of 10.0 per
cent. Soya flour, which is a solvent extracted soya flour used in such mix shall
conform to the standards of soya flour laid down under item A.18.15. It shall be free
from insect or fungus infestation, odour and rancid taste. It shall not contain added
flavouring and colouring agents or any other extraneous matter.
A.18.02.01----FORTIFIED MAIDA means the product obtained by adding nutrients
to maida.
A.18.02.02----PROTEIN RICH (PAUSHTIK) MAIDA means the product obtained
by mixing maida (wheat flour) with groundnut flour or soya flour or combination of
both up to an extent of 10.0 per cent. Soya flour which is a solvent extracted flour
used in such mix shall conform to the standards of soya flour laid down under
Solvent Extracted Oil, Deoiled Meal and Edible Flour (Control) Order, 1967. It shall
be free from insect or fungus infestation, odour and rancid taste. It shall not contain
added flavouring and colouring agents or any other extraneous matter.
A.18.03----SEMOLINA (SUJI or RAWA) means the product prepared from clean
wheat free from rodent hair and excreta by process of grinding and bolting.
A.18.05.01---WHOLE MEAL BARLEY POWDER OR BARLEY FLOUR OR
CHOKER (yukt Jau ka Churan) means the product obtained by grinding clean and
sound dehusked barley (Hordeum vulgare or Hordeum vulgare or Hordeum
distichun) grains free from rodent hair and excreta.
Flours differ from the grains in the extent to which the grain has been subdivided.
You may recall studying about the structure of a cereal grain in Unit 9, section 9.8.
We studied that the kernel consists of four parts: the seed coat (pericarp), the fruit
coat (aleurone layer), the endosperm and the germ, or embryo. Figure 3.1 depicts
these parts.
Whole wheat flour is formed when the entire kernel is sufficiently subdivided. White
flour is obtained when the endosperm is reduced to particles of a small size. Not all
the flours are alike and it is this property that makes them suitable for different
preparations such as chapatis, breads, biscuits, cakes, buns, pastas and so on. As flour
requirement for different operations vary, thus, it is very important to study the flour
43
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Science
characteristics. The next section focuses on the study of the characteristics of various
flours.
Figure 3.1: The cereal grain
3.3
CHARACTERISTICS OF VARIOUS FLOURS
Flours are characterized on various parameters as moisture content, total ash, acid
insoluble ash, gluten content and alcoholic acidity. These parameters are highlighted
in Table 3.1.
Table 3.1: Flour characteristics and their values
Flour Characteristics
Wheat flour
Maida
Suji
Paushtik atta
Moisture (when determined by
heating at 130-133 degree C for
2 hours). Percentage (max)
14.0
14.0
14.5
14.0
Total ash percent (on dry weight
basis) (max)
2.0
1.0
1.0
2.75
Ash insoluble in dilute HCI
percent(on dry weight
basis).(max)
0.15
0.1
0.1
0.1
Gluten percent (on dry weight
basis) (min)
6.0
7.5
6.0
-
Crude fiber percent (on dry
weight basis) (max)
-
-
0.53
2.5
Alcoholic acidity percent (with
90 per cent alcohol) expressed as
H2SO4
(on dry weight basis) (max)
0.18
0.12
0.18
0.12
Source: Prevention of Food Adulteration Act, 1955
Max : Maximum
Min : Minimum
Let us next look at each of these characteristics in greater details. We begin with
moisture content.
44
3.3.1 Moisture Content
Experiments on the
Chemistry of Cereals
Moisture content of the flour is an important parameter and does not remain the same
throughout the period of storage. As the food grains respire and produce heat, water
and carbon dioxide, being porous absorb and give out moisture to maintain
equilibrium with the humidity in environment. It is free water that is held by capillary
force that fluctuates with the environment. Thus, the amount of free water determines
the rate of deterioration in grains and flour. During the milling processes in the
preparation of flour, the husk is structurally separated from the seed thus making the
moisture absorption an easier process.
Increase in moisture content encourages mould growth. Moisture moves from one
portion of the stored mass of flour to another, either due to temperature gradient or
due to differences of temperature between flour particles and environment and this
migration leads to caking associated with growth of mould and yeast.
3.3.2 Ash Content
Ash content of a foodstuff represents inorganic residue remaining after destruction of
organic matter. It may not be the exact measure of the total mineral content as some
changes may occur due to volatilization of some components or some interaction
between constituents. High ash content or a lower alkalinity of ash may be suggestive
of the presence of adulterants. The process of combustion evaporates moisture and
oxidizes the organic matter to vanish in air. The incombustible residue is the ash. The
major constituents of the ash in flours are calcium, phosphorus, iron, sodium,
potassium, halogens, silica or sand or silicious matter. The complete ashing is
indicated by the absence of ember like glow in the ash when the crucible is observed
immediately after taking it out of the furnace.
3.3.3 Gluten Content
What is gluten? Certainly you know that gluten is the protein found in wheat. Gluten
is more or less made up of equal parts of gliadin and glutenin. Look up section 4.3 in
the theory course (MFN-008) under the dough formation function to recapitulate
what you learnt about gluten and its functional properties, particulary with respect to
dough formation. This will help you understand the behaviour of gluten more
precisely.
The flour absorption is the amount of water that flour can take up and hold while
being made into simple dough.
Cake flour has 7-9% protein, all purpose flour has protein content of 9-10%. Bread
flour has a protein content of 12.5-13.5 per cent. The protein consists of ~80%
gluten. Gluten of cake flour is weakest, whereas, that of bread flour is the strongest.
Flour is graded as to its strength depending on its gluten content whether, weak,
medium and strong. Let us see how flours are graded based on the gluten content.
Weak flour (also known as soft flour or hi-ratio flour) has a low gluten content of
approximately 8% and is therefore ideal for delicate cake and sponge production.
Medium flour (also known as all purpose flour) is produced so that it is suitable for
products that have to be chemically aerated. It is weak enough to stop toughening but
strong enough to stand the pressures of the gases resulting from the use of baking
powders etc. It is also a good all round flour for bread-crumbing, batters, scones etc.
Strong flour has a high gluten content that makes it ideal for yeast products, breads
and puff pastry.
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Durum wheat flour (also known as Durum flour and semolina flour) is specially
produced for the production of pastas.
The strength of flour can be tested by squeezing the flour in the hand. The following
conclusions may be derived:
•
a weak flour will cling together when the hand is open
•
a strong flour will crumble to flour again
Wheat flour is made up of 12% protein, 80% carbohydrate, 2% lipid and the
remaining 6% as ash and water. For example, if you use 100 grams of flour to
conduct your gluten experiment, one would expect that 12 grams (or 12%) of the
material would remain as proteins.
Wheat protein is made up of four general proteins: albumins, globulins, glutenin and
gliadin. Albumins and globulins are water soluble thus would wash out during the
"running under the water" step. Glutenin and gliadin are the two proteins that, we
already know, make up gluten. These two proteins are not water soluble thus would
not be washed down the drain by cold running water. This is an important
characteristic.
3.3.4 Crude and Dietary Fibre
Crude fibre is the organic residue which remains after the food sample has been
treated with boiling dilute sulphuric acid, boiling dilute sodium hydroxide solution
and alcohol. The crude fibre consists of cellulose together with a little lignin. Crude
fibre estimation is of great value in judging the quality of wheat products, particularly
flours. High crude fibre foods are low in nutritional value. It also reflects the
efficiency of milling and separation of bran from the starchy endosperm. Further,
crude fibre is a more direct index of flour purity than ash or colour.
Dietary fibre
Dietary fibre is an imporatant ingredient in food and comprises of a diverse group of
plant substances viz. celluloses, hemicelluloses, lignins, gums, mucilages and
phenolic compounds which are resistant to hydrolysis by digestive enzymes of the
human gut regions. We have already studied about these substances in Unit 2 in the
theory booklet.
Crude fibre and hemicellulose are the major components of dietary fibre as crude
fibre itself is made up of cellulose and lignin.
3.3.5 Alcoholic Acidity
Alcoholic acidity is defined as mg of H2SO4 required for 100 g of the sample to have
the same alcohol soluble acids.
Grains or their milled products on storage undergo physical, as well as, chemical
changes. Acid phosphates, amino acids and free fatty acids of flours, under certain
conditions increase considerably due to the enzymatic hydrolysis of phytin, protein
and fat, respectively. Milled products deteriorate faster than their parent grains. The
amino acids and acid phosphates are soluble in strong alcohol. The free fatty acids
are insoluble in water but are soluble in fat solvents or in strong alcohol. For this
reason, the acidity in flours is expressed as either fat acidity wherein benzene is used
as a fat solvent or it is expressed as alcoholic acidity.
Now let us study the analysis of the various parameters of flour in the following
activities and see whether the given samples of flour conform to the laid down
standards.
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Experiments on the
Chemistry of Cereals
ACTIVITY
1
DETERMINATION OF THE MOISTURE CONTENT
Aim: To determine the moisture content in the given sample of flour.
Objectives
Date: ………….
After undertaking this activity, you will be able to:
• assess the moisture content in the given sample of flour,
• determine the moisture content for dry samples, and
• check the given sample for conformance to the standard for moisture content.
Principle
Moisture content in the flour can be determined by:
i)
Oven Drying method, and
ii) Infrared heating
The principle behind each of these methods is given herewith:
Oven drying
This method consists of measuring the weight lost by foods due to evaporation of
water. However, loss of weight may not be a true measure, as in the foods high in
protein content, only a proportion of "free water" present may be evaporated at the
drying temperature. The remaining which is referred to as "bound water" may still
remain associated with the proteins present in the food. The proportion of the loss of
free water increases as the temperature of drying increases. Thus, it is important to
control the conditions of time and temperature during the estimation.
Infrared heating
Infrared moisture balance is an instrument for measuring the moisture content of
materials that do not change their chemical structure while losing water under
exposure to infrared radiation. A graduated scale gives continuous percentage reading
of the loss of weight of the sample due to the loss of moisture. Since, drying and
weighing are simultaneous, this instrument is especially useful in measuring the
moisture content of substances that quickly reabsorb moisture.
Materials Required
Collect the following material for carrying out the activity:
•
•
•
•
•
Sample of flour
Moisture dish-made of porcelain, silica, glass or aluminium
Oven-electric, maintained at 130 ± 2°C.
Desiccator
Weighing balance
Procedure
Now carry out the practical step-by-step as enumerated herewith:
1) Weigh accurately about 5 g of the sample in the moisture dish, previously dried
in the oven and weighed.
2) Place the dish in the oven maintained at 130 ± 2°C for 2 hours.
3) Cool in the dessicator and weigh.
4) Repeat the process of drying, cooling and weighing at 30 minutes intervals until
the difference between two consecutive weighings is less than one milligram.
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5) Record the lowest weight.
6) Calculate the moisture percent by weight as per the formula given herewith.
Calculations
Moisture percent by weight =
100(W1− W2)
W1 − W
where,
W1 = weight in g of the dish with the material before drying
W2 = weight in g of the dish with the material after drying to constant weight, and
W = weight in g of the empty dish.
Precautions
1) The oven-dried sample should not be kept in open but in the dessicator before
weighing.
2) The process of drying should be repeated till the difference in the weighings
should be less than 1 mg.
3) The oven temperature should be regulated throughout the process of drying.
Observation and Findings
Now, record your findings herewith:
W = …………… g
W1 = …………… g
W2 = …………… g
Next, calculate the total moisture content according to the formula given above.
Calculations
Moisture % by weight =
Inference
The given sample of flour has ………….. % moisture by weight. The maximum limit
for the moisture content according to PFA, is ………………. % by weight.
Conclusion
(Comment regarding the acceptability of the sample)
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
Submit the activity for evaluation.
……………………………….
Counsellor Signature
48
Experiments on the
Chemistry of Cereals
ACTIVITY
2
DETERMINATION OF THE TOTAL ASH CONTENT
Aim: To determine the total ash content in the given sample of flour.
Date: ………….
Objectives
After undertaking this activity, you will be able to:
• assess the mineral content in the given sample of flour,
• check the given sample for conformance to the standard for ash content,
• determine the total mineral content for dry samples, and
• estimate the increase in mineral content due to any fortification / enrichment of
the flour.
Principle
Ash content of a foodstuff represents inorganic residue remaining after destruction of
organic matter. It may not be the exact measure of the total mineral content, as some
changes may occur due to volatilization of some components or some interaction
between constituents. High ash content or a lower alkalinity of ash may be suggestive
of the presence of adulterants. The acid-insoluble ash is a measure of sand and other
silicious matter present. The process of combustion evaporates moisture and oxidizes
the organic matter to vanish in air. The incombustible residue is the ash. The major
constituents of the ash in flours are calcium, phosphorus, iron, sodium, potassium,
halogens, silica or sand or silicious matter.
During the process of ashing, if the temperature crosses 570°C, then some of the
inorganic salts in the ash get fused. Although, such fusion may not affect the total ash
content of a sample but it affects the acid-insoluble ash. Over-heated ashes reflect a
metallic tinge of the cations present. Copper imparts a greenish tinge, iron imparts a
brownish and alkali metals a greyish tinge. Incomplete ashing gives a black tinge.
The complete ashing is indicated by the absence of ember like glow in the ash when
the crucible is observed immediately after taking it out of the furnace.
Ash is significant for the miller because it is an indicator of the quality of the streams
that are included in the flour. Ash content in the wheat kernel is higher near the bran
layer or outside of the kernel. The center of the kernel has the lowest ash content.
Materials Required
Collect the following material to carry out the activity:
• Sample of flour
• Flat-bottom dish – of stainless steel, porcelain, silica or platinum.
• Muffle Furnace – maintained at 550 ± 10°C.
• Desiccator
• Weighing balance
Procedure
Now carry out the practical step-by-step as enumerated herewith:
1) Weigh accurately about 3-5 g of the sample in the dish, previously dried in the
air oven and weighed.
2) Heat the dish gently on a flame at first and then strongly in a muffle furnace at
550 ± 10°C till grey ash results.
3) Cool in the dessicator and weigh.
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4) Repeat the process of heating in muffle furnace, cooling and weighing at 30
minutes intervals until the difference between two consecutive weighings is less
than one milligram.
5) Record the lowest weight.
Note: Preserve the dish containing the ash for the determination of acid–insoluble
ash.
6) Calculate the total ash content according to the formula given herewith.
Calculations
Total Ash (% by weight) =
100(W1− W2)
W1 − W
where,
W2 = weight in g of the dish with ash.
W1 = weight in g of the dish with the material taken for test.
W
= weight in g of the empty dish.
Precautions
1) Ashing should be done completely.
2) The process of drying should be repeated till the difference in the weighings
should be less than 1 mg.
3) The temperature of the furnace should be regulated throughout the process of
ashing.
Findings
Record your findings herewith.
W = ………….g
W1 = …………. g
W2 = …………. g
Next, calculate the total ash content according to the formula given above.
Calculations
Total ash % by weight =
Inference
The given sample of flour has ………………… % ash by weight. The maximum
limit for the ash content according to PFA, is ………………… % by weight.
50
Conclusion
Experiments on the
Chemistry of Cereals
(Comment regarding the acceptability of the sample)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
……………………………..
Counsellor Signature
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ACTIVITY
3
DETERMINATION OF THE ACID INSOLUBLE ASH
Date: ………….
Aim: To determine the acid insoluble ash in the given sample of flour.
Objectives
After undertaking this activity, you will be able to:
• assess the mineral content in the given sample of flour,
• check the given sample for conformance to the standard for ash content, and
• determine the acid insoluble mineral content for dry samples.
Principle
Ash content of a foodstuff represents inorganic residue remaining after destruction of
organic matter. High ash content or a lower alkalinity of ash may be suggestive of the
presence of adulterants. The acid-insoluble ash is a measure of sand and other
silicious matter present. Overheating of ash results in the fusion of some of the
inorganic salts which affects the acid-insoluble ash. During the process of
overheating, the ashed material changes from the molecular to the polymerized form
and boiling with 1:9 hydrochloric acid (HCl) does not remove the acid soluble
constituents of the total ash as the acid is not able to act on the entire periphery of
each molecule. Thus, many components remain unreacted and insoluble in acid and
results in the higher value of acid-insoluble ash.
Materials Required
Collect the following material for conducting the activity:
•
•
•
•
•
•
•
Sample of flour
Dilute hydrochloric acid (HCl)
Flat-bottom dish – of stainless steel, porcelain, silica or platinum.
Muffle Furnace-maintained at 550 ± 10°C.
Desiccator
Weighing balance
Whatman number 42 filter paper
Procedure
Now carry out the practical step-by-step as enumerated herewith:
1) Weigh accurately about 3-5 g of the sample in the dish, previously dried in the
air oven and weighed.
2) Heat the dish gently on a flame at first and then strongly in a muffle furnace at
550 ± 10°C till grey ash results.
3) Cool in the dessicator and weigh.
4) Repeat the process of heating in muffle furnace, cooling and weighing at 30
minutes intervals until the difference between two consecutive weighings is less
than one milligram.
5) Record the lowest weight.
6) To the ash contained in the dish, add 25 ml of dilute hydrochloric acid.
7) Cover with watch-glass and heat on a water bath for 10 minutes.
8) Allow to cool and filter the contents of the dish through a whatman filter paper
no. 42.
52
9) Wash the filter paper with water until the washings are free from the acid and
return them to the dish.
Experiments on the
Chemistry of Cereals
10) Keep it in an oven maintained at 100 ± 2°C for about 3 hours.
11) Ignite in a muffle furnace at 550 ± 10°C for one hour.
12) Cool the dish in a desiccator and weigh.
13) Heat the dish again at 550 ± 10°C for 30 minutes, cool in the desiccator and
weigh.
14) Repeat this process of heating for 30 minutes, cooling and weighings until the
difference between two successive weighings is less than one milligram. Record
the lowest weight.
15) Calculating the acid-insoluble ash, using the formula given herewith:
Calculations
Acid insoluble ash, percent weight =
100 (W2 − W)
W1 − W
where,
W2 = weight in g of the dish with the acid insoluble ash.
W1 = weight in g of the dish with the material taken for test.
W
= weight in g of the empty dish.
Precautions
1) Ashing should be done completely.
2) The process of drying should be repeated till the difference in the weighings
should be less than 1 mg.
3) The temperature of the furnace should be regulated throughout the process of
ashing.
Findings
Record your findings herewith.
W
= ……………. g
W1 = ……………. g
W2 = ……………. g
Next, calculate the acid insoluble ash content according to the formula given above.
Acid insoluble ash % by weight =
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Inference
The given sample of flour has …………….. % acid insoluble ash by weight. The
maximum limit for acid-insoluble ash content according to PFA, is
% by weight.
Conclusion
(Comment regarding the acceptability of the sample)
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
Submit the activity for evaluation.
………………………………………
Counselor Signature
54
Experiments on the
Chemistry of Cereals
DETERMINATION OF THE CRUDE FIBRE CONTENT IN
THE GIVEN SAMPLE OF FLOUR
Aim: To determine the crude fibre content in the given sample of flour.
ACTIVITY
4
Date: ………….
Objectives
After undertaking this activity, you will be able to:
• assess the crude fibre content the given sample of flour,
• check the given sample for conformance to the standard for crude fibre content,
and
• determine the indigestible residue for dry samples.
Principle
Crude fibre is the organic residue which remains after the food sample has been
treated with boiling dilute sulphuric acid, boiling dilute sodium hydroxide solution
and alcohol. The crude fibre consists of cellulose together with a little lignin. Crude
fibre estimation is of great value in judging the quality of wheat products,
particularly flours. High crude fibre foods are low in nutritional value. It also reflects
the efficiency of milling and separation of bran from the starchy endosperm. Further,
crude fibre is a more direct index of flour purity than ash or colour.
For determining crude fibre, the material is passed through the soxhlet’s extractor for
dissolving the fat so that the defatted residue is more receptive to the alkali or acid
treatment.
On refluxing with 1.25% sulphuric acid (H2SO4), the fat present within the cell walls
gets dislodged. The starches are hydrolyzed to soluble saccharides. The soluble
minerals are washed out and some of the proteins are hydrolyzed to soluble forms.
Treatment with 1.25% sodium hydroxide (NaOH) results in the hydrolysis of
remaining proteins. This treatment removes tannins and fats. The fats form soaps and
are washed out during hot water washings. The unreacted alkali and the sodium soaps
must be completely washed off otherwise, after washing, free alkali gets converted to
its oxide leaving black residue even after ignition in the muffle furnace.
Materials Required
Collect the following material for conducting the activity:
• Sample of flour
• Flat-bottom dish – of stainless steel, porcelain, silica or platinum.
• Muffle Furnace-maintained at 550 ± 10°C.
• Desiccator
• Weighing balance
• 1.25% H2SO4
• 1.25 % NaOH
• Reflux condenser
• Funnel
• Filter paper
Procedure
Now carry out the practical step-by-step as enumerated herewith:
1)
Weigh accurately about 3-5 g of the sample in flask of the reflux condenser.
2)
Add 200 ml boiling 1.25% H2SO4 solution in the flask.
3)
Reflux* for at least half an hour.
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*Refluxing means to avoid the loss of volatile components during the process
of heating on low flame. This is made possible by use of reflux condenser.
However, if the condenser is not available, then a conical flask with cotton plug
may be used. It should be noted that the latter procedure might result in some
losses and thus cannot be regarded as the standard procedure.
4)
Remove from the flame and add 50 ml of cold water to the solution and filter it
through the filter paper.
5)
Wash the residue on the filter paper with boiling water until the washings are
no longer acid to litmus (acid turns red litmus to blue).
6)
Return the residue to the condenser/conical flask.
7)
Add 200 ml boiling 1.25% NaOH solution.
8)
Reflux for at least half an hour.
9)
Remove from the flame and add 50 ml of cold water to the solution and filter it
through the filter paper.
10)
Wash the residue on the filter paper with boiling water until the washings are
no longer alkaline to litmus (alkaline medium turns blue litmus to red).
11)
Now take the residue to the and wash with traces of organic solvent.
12)
Put the residue in the crucible and dry it in oven at 103°C to 105°C.
13)
Allow to cool and then weigh.
14)
Now put the crucible in the muffle furnace and ash the contents.
15)
Cool and weigh.
16)
Use the following formula for calculating the crude fibre percent by weight
present in the sample.
Calculations
Crude fibre, percent by weight =
100(W2 − W3)
W1 − W
where,
W2 = weight in g of the dish with oven dried residue.
W3 = weight in g of the dish with ash
W1 = weight in g of the dish with the material taken for test.
W
= weight in g of the empty dish.
Precautions
1) The residue should be free from any acid or alkali. Thus it should be washed
thoroughly.
2) Ashing should be done completely.
3) The process of drying should be repeated till the difference in the weighings
should be less than 1 mg.
4) The temperature of the furnace should be regulated throughout the process of
ashing.
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Experiments on the
Chemistry of Cereals
Findings
Record your findings herewith.
W = ………….. g
W1 = …………..g
W2 = ………….. g
W3 = ………….. g
Next, calculate the crude fibre percent by weight present in the sample using the
formula given above.
Calculations
Crude fibre % by weight =
Inference
The given sample of flour has …………………… % crude fibre. The maximum
limit for the crude fibre according to PFA, is …………………………% by weight.
Conclusion
(Comment regarding the acceptability of the sample)
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
Submit the activity for evaluation.
……………………………..
Counsellor Signature
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ACTIVITY
5
Date: ………….
DETERMINATION OF THE GLUTEN CONTENT
Aim: To determine the gluten content in the given sample of flour.
Objectives
After undertaking this activity, you will be able to:
• assess the gluten content the given sample of flour,
•
check the given sample for conformance to the standard for gluten content, and
•
determine the water absorption power of the given sample of flour.
Principle
Gluten is made up of gliadin and glutenin. It is the water-insoluble portion of the
wheat atta obtained by washing away the starch, as well as, the bran from the dough.
Hydrated gluten contains about 66-67% water, and when dried, it becomes sticky or
adhesive. During dough fermentation the gluten forms cells which retain CO2 and
cause the bread to swell. Gluten is insoluble in water at pH 7 but is readily soluble in
acidic or basic aqueous solutions of low ionic strength, therefore it should be noted
that the water used for making the dough and washing away need not be distilled
water but must be neutral and free from chlorine.
Materials Required
Collect the following material for conducting the activity:
•
Sample of flour
•
Flat-bottom dish – of stainless steel, porcelain, silica or platinum
•
Weighing balance
•
Burette
•
Spatula
•
Muslin cloth
•
Butter paper
•
Oven
Procedure
Now carry out the practical step-by-step as enumerated herewith:
58
1)
Weigh 25 g of the flour sample. Put in china dish and add water from burette.
2)
Measure the volume of water used to make a soft dough.
3)
Keep the dough in a beaker filled with water for half an hour.
4)
Now wash this dough with water and keep on removing the starch till clean
water comes out.
5)
Do iodine test to confirm that dough is free of starch.
6)
Take this extracted gluten and weigh.
7)
Dry it in oven maintained at 130 ± 1°C for 2 hours.
8)
Keep in the dessicator, let it cool and weigh.
9)
Calculate the gluten content of the sample using the following formula.
Calculations
Gluten content, percent =
100(W2 − W3)
W
Experiments on the
Chemistry of Cereals
where,
W2 = weight in g of the wet gluten
W3 = weight in g of the dried gluten
W
= weight in g of the flour taken for analysis.
Water Absorption Power
25 g of flour required (Y) ml of water to make a soft dough.
∴100 g of flour would require = (Y × 100/ 25) ml of water.
Precautions
1) The dough should be washed carefully without the loss of any gluten.
2) Iodine test should be performed to check that the dough should be free of any
starch.
Findings
Record your findings herewith.
W = ………….. g
W2 = ………….. g
W3 = ………….. g
Next, calculate the gluten content using the formula given above.
Calculations
Write the formula and calculate the following:
Gluten % by weight =
Water absorption power :
Water absorption power of the given flour is ………….. percent
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Inference
The given sample of flour has …………………………… % gluten.
Conclusion
(Comment regarding the acceptability of the sample)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
…………………………….
Counsellor Signature
60
Experiments on the
Chemistry of Cereals
DETERMINATION OF THE ALCOHOLIC ACIDITY OF
THE GIVEN SAMPLE OF FLOUR
Aim: To determine the alcoholic acidity of the given sample of flour.
ACTIVITY
6
Date: ………….
Objectives
After undertaking this activity, you will be able to:
•
assess the acidity the given sample of flour, and
•
check the given sample for conformance to the standard for its acidity.
Principle
Alcoholic acidity is defined as mg of H2SO4 required for 100 g of the sample to have
the same alcohol soluble acids.
Grains or their milled products on storage undergo physical, as well as, chemical
changes. Acid phosphates, amino acids and free fatty acids of flours, under certain
conditions increase considerably due to the enzymatic hydrolysis of phytin, protein
and fat, respectively. Milled products deteriorate faster than their parent grains. The
amino acids and acid phosphates are soluble in strong alcohol. The free fatty acids
are insoluble in water but are soluble in fat solvents or in strong alcohol. For this
reason, the acidity in flours is expressed as either fat acidity,wherein, benzene is used
as a fat solvent or it is expressed as alcoholic acidity.
Materials Required
Collect the following material to carry out the activity:
•
Sample of flour
•
Conical flask
•
Weighing balance
•
Pipette
•
Standard NaOH solution (approximately 0.05 N)
•
Phenolphthalein
•
Neutral ethyl alcohol- 90% volume by volume
Procedure
Now carry out the practical step-by-step as enumerated herewith:
1) Weigh 5 g of the flour sample. Put in conical flask.
2) Add 50 ml of neutral ethyl alcohol.
3) Stopper the flask, shake and allow to stand for 24 hours.
4) Filter the alcoholic extract (through an ordinary dry filter paper).
5) Titrate 10 ml of alcoholic extract against standard NaOH solution using
phenolphthalein as indicator.
6) Calculate the percentage alcoholic acidity as sulphuric acid.
7) Calculate the alcoholic acidity of the sample using the following formula.
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Calculations
Alcoholic acidity, percent by weight =
22.52 × AN
W
where,
A = Volume in ml of standard NaOH used in titration.
N = Normality of standard NaOH solution used in titration (i.e 0.05 N)
W = weight in g of the flour taken for analysis.
Findings
Record your findings herewith.
A = …………. ml
N = …………. N
W = …………. g
Next, calculate the alcoholic acidity of the given sample using the formula given
above.
Calculations
Alcoholic acidity percent as sulphuric acid:
Inference
The given sample of flour has …………………….. % acidity as alcoholic acidity.
The maximum alcoholic acidity percent according to the specification is…….. .
Conclusion
(Comment regarding the acceptability of the sample)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
…………………………….
Counsellor Signature
62
PRACTICAL 4
FATS AND OILS
Fats and Oils
Structure
4.1
4.2
4.3
4.4
Introduction
Fats and Oils
Analytical Tests for Fats and Oils
Assessment of the Quality of Edible Oils/Fats
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
4.4.6
Moisture Content
Colour
Impurities
Acid Value and Free Fatty Acids
Peroxide Test
Purity Tests
Activity 1: Determination of Moisture Content
Activity 2: Determination of Impurities
Activity 3: Determination of Acid Value and Free Fatty Acids
Activity 4: Determination of Peroxide Value
Activity 5: Purity Tests of Oils/Fats
4.1
INTRODUCTION
We have already studied about the structure, properties and functional role of fats and
oils in the theory Course (MFN-008) in Unit 3. We suggest you look up the unit once
again before you start with this practical on fats and oils which focuses on
determination and assessment of the quality of fats and oils.
Objectives
After undertaking this practical and the activities given herewith, you will be able to:
•
determine the nature of fat or oil or the blends to see whether it is of the type
required or specified, and
•
assess the quality of fat in terms of moisture content, colour, impurities, acid
value, purity.
4.2
FATS AND OILS
Oils and fats form an integral part of the dietaries the world over. In the body they are
the primary source of energy. As you know, chemically they are complex mixtures of
esters of fatty acids and glycerol. Fat in the liquid state is known as oil. There are
various types of fatty acids present, which may be saturated or unsaturated in nature.
Hence, the composition of different fats/oils depends upon the types of fatty acids
present namely, stearic, oleic, palmitic, recinolic etc. Table 4.1 gives you fatty acid
composition of some edible fats and oils. Different forms of oils or fats are available
namely, crude oil, refined oil, lard, hydrogenated fats, butter, ghee, margarine and
shortenings. You will note that acidity in oils/fats is frequently expressed as the
percentage of free fatty acids present in the sample. The percentage of free fatty acid
in most of the oils and fats is calculated on the basis of oleic acid, although in
coconut oil and palm kernel oil it is often calculated in terms of lauric acid, in castor
oil in terms of ricinoleic acid and in palm oil in terms of palmitic acid. However, the
overall composition of fatty acids in a given sample of oil/fat is conducted through
GLC (Gas Liquid Chromatography technique).
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Table 4.1
The type of oil/fat also depends upon the source of extraction.
64
Animal sources provide us with fish oils and fats, milk fat, lard, beef fat and tallow.
Nut oils and fats, seed oils and bran oils are obtained from the plant sources. The
crude oil is obtained from plant seeds and nuts by expelling or extraction with
solvents, whereas, fats from the animal tissue is obtained by the process of rendering.
These crude oils/fats contain suspended impurities, moisture and higher percentage of
free fatty acids.
Fats and Oils
The production of edible oils usually involves the process of alkali refining,
bleaching and deodorization of the crude oils. These processes are designed to
remove suspended impurities and the substances which are responsible for colour,
unpleasant flavour and those substances which either act as catalysts or are associated
with rancidity.
Hydrogenation involves the catalytic addition of hydrogen to highly unsaturated
liquid oils thereby converting them to solid fats. These oils are not susceptible to the
process of hydrolytic rancidity.
We have just recapitulated the basic concept of fats and oils, which you may recall
studying in Unit 3 in the theory booklet. With this basic understanding, we move on
to the study of the analytical tests in fats and oils.
4.3
ANALYTICAL TESTS FOR FATS AND OILS
The analytical tests used in fats and oils are to:
•
determine the nature of fat or oil or the blends to see whether it is of the type
required or specified, and
•
assess the quality of fat.
Many tests are involved to evaluate these two factors involving the physical analysis
and chemical analysis. However, due to the complexities and time constraints, only a
few tests are being discussed in this unit. Only the tests to determine the quality of
fats/oils are being undertaken.
Let us first of all become familiar with the quality parameter requirements for
fats/oils.
It may be necessary to assess the quality of either "crude" oils or "refined and
deodorised" oils. For the former (crude oils), the specified criteria are usually
moisture, impurities, colour and free fatty acid contents and tests for adulteration are
used while for the latter (refined/deodorized oils), flavour, FFA content, moisture,
colour, rancidity, adulteration and stability to autoxidation are the minimum
requirements for reliable judgment. In this practical we will be conducting the
important tests for purity.
The physiochemical characteristics of the fats/oils have been covered under
paragraph A.10 of Appendix B of PFA Rules. Some of the specifications laid down
by PFA/AGMARK for vanaspati and mustard oil are listed in Table 4.2
Table 4.2: Specifications laid down by PFA/AGMARK for vanaspati and mustard oil
Parameters
Mustard oil specifications
Vanaspati oil specification
0.25
0.25
50
--
1.4646-1.4662
---
Saponification value
168-177
--
Iodine value
96-112
---
Moisture content % max
Colour by lovibond tintometer in
1/4" cell expressed as Y+5R
(max)
Refractive index at 40 DC
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Free fatty Acid %max
---
0.25
1.20
2.0
Negative
Positive
----
2.0 red (min)
BR reading at 40 DC
58-60.5
--
Rancidity test
Negative
Negative
Nil
Nil
Negative
Negative
Characteristic
Characteristic
Test for Argemone oil
Negative
Negative
Test for Hydrocyanic acid
Negative
Negative
Polybromide test
Negative
Negative
Unsaponifiable matter %max
Baudauin test
Colour produced by baudauin test
Suspended and foreign matter
Test for mineral oil
Taste and flavour
Source: Prevention of Food Adulteration Act, 1954
After learning about the specifications for oils lay down by PFA, let us get to know
about the procedures for conducting these tests. We will not be covering the tests for
determining the nature of oils/fats like iodine value, unsaponifiable matter, since you
will be covering these in the Nutritional Biochemistry Practical. The tests, which are
required for quality assessment, would be covered here in the subsequent section and
in the experiments included herewith.
4.4
ASSESSMENT OF THE QUALITY OF EDIBLE
OILS/FATS
Various parameters are used for the assessment of the quality of fats and oils. Some
of the important ones include determination of moisture content, colour, impurities,
acid value, peroxide value and tests for the presence of adulterants in fats and oils.
Let us review these parameters one by one, starting with the moisture content.
4.4.1 Moisture Content
Moisture content of the fats/oils is an important parameter and does not remain the
same throughout the period of storage. More the moisture content, more prone is the
fat to the process of hydrolytic rancidity. In this process, the triglyceride reacts with
water and for each molecule of water involved, one molecule of fatty acid is released.
When a molecule of fat reacts with three molecules of water, glycerol and three fatty
acids are formed as shown in Figure 4.1
Figure 4.1: Triglyceride reacts with water to give glycerol and fatty acids
66
Thus, it is very important to control the moisture content in the oils/fats which
otherwise would lead to the development of off flavours.
Fats and Oils
4.4.2 Colour
The colour of the oil is of considerable importance commercially and is an agreed
standard of comparison. The colours of oils are usually declared in Lovibond units,
and may be measured in an instrument designed for the same.
The instrument includes a standard light source, glass ended cells of accurate length
and the series of coloured glasses of yellow, red and blue colour. The colour of the
oil is matched by a suitable combination of them. For an accurate analysis, it is
important to keep the following points in mind:
•
•
•
Number of matching glasses should be kept to a minimum.
The oil must be clear and bright, filtration should be done if required.
The oil should not be heated to an extent so that it affects the colour of the oil.
The dimensions of the cell used and the mode of expressing the colour readings for
different oils as given by BIS in SP:18 (Part XIII) -1984 shall be as indicated in
Table 4.3.
Table 4.3: Colour reading for different oils as given by Bureau of Indian Standards
Oil/Fat
Size-Designation of
cell (in)
Mode of expressing colour reading
Castor
1
Y+5R
Groundnut
1
Y+5R
Coconut
1
Y+5R
Sesame
1/4
Y+5R
Mustard
1/4
Y+5R
Mahua
1/4
Y+5R
Cottonseed (washed
and refined)
1/4
Y+10R
4.4.3 Impurities
The impurities or total dirt in an oil/fat consist of the sum of all mineral matter
present together with the organic constituents, exclusive of water and volatile matter,
which are not dissolved by a specified solvent applied under specified conditions.
The total impurities can be separately estimated for total dirt and organic dirt.
4.4.4 Acid Value and Free Fatty Acids (FFA)
Acid value is a measure of hydrolytic rancidity present in the sample of oil/fat. It
reflects the state of freshness or deterioration of the material and also the quantity of
glycerols to be released as a result of neutralization of fat/oil. It has a wide
implication in the oil refining industry as it gives the fair idea of the state of oil/fat
and also the total quantity of alkali required to neutralize a particular batch of oil or
fat to make it suitable for the purpose of hydrogenation. Acidity also helps in
predicting the quantity of oil or fat, which will pass into soap stock as a compulsive
by-product of the refining process.
High acidity oils or fats produce excess smoke during heating. Moisture content,
temperature of heating, duration of heating, type of metal container are parameters
which act as catalysts to the process of hydrolysis in fats or oils.
Acidity is expressed as FFA% on oleic acid basis like in ghee. However, in certain
oils and fats it is expressed on the basis of the fatty acids which are predominant. For
example, castor oil which has 86-94% recinoleic acid, coconut oil having its fatty
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acid composition as lauric acid- 44-51%, palmitic acid 7-11%, capric 5-9% and palm
oil which contains 35-50% palmitic acid.
In India, we have the Agmark specifications, the PFA Act specifications, as well as,
BIS specifications to denote acidity of fats and oils.
4.4.5 Peroxide Value
Autoxidation leads to the development of off-flavours and objectionable taste in fats.
The initial oxidation products that are formed are hydroperoxides and are measured
by iodimetric methods. The peroxide value of the freshly deodorized fat should be nil
and a fat received directly from a processor should seldom exceed a peroxide value
of 1.0. Most fats are deemed rancid when their peroxide values are between 10 and
20.
4.4.6 Purity Tests
Purity tests for oils/fats would include analyzing the samples for the presence of
sesame oil, cottonseed oil, linseed oil, argemone oil, hydrocyanic acid, mineral oil,
mobile oil, groundnut oil, kusum oil or the presence of animal fats in vegetable oils.
However, we will be covering only a few considering their feasibility in the
laboratories.
A) Test for the presence of sesame oil
The development of pink colour with furfural solution in the presence of
hydrochloric acid (HCl) indicates the presence of sesame oil. This test is also known
as BAUDOUIN Test. Generally this test is also used to check adulteration in the
sample of ghee. The test results should be positive for vanaspati and negative for all
other samples of ghee, oils and fats.
B) Test for the presence of linseed oil (HEXABROMIDE TEST)
Hexabromide test is done to know the extent of presence of linolenic acid. In
presence of fish oils, which are rich in linolenic acid, the test gives precipitates where
as if other oils like rapeseed oil are present, the test gives a clear solution. Animal
fats may give turbidity when tested in this way. Thus, this test is carried out to test
the presence of linolenic acids in the samples.
C) Test for the presence of argemone oil
This test helps to detect the presence of argemone oil. Argemone mexicana is the
plant, which yields seeds of this oil. The seeds are very small similar to black
mustard seeds but has striations and pointed end. Oil extracted from these seeds is
toxic in nature and results in epidemic dropsy. These toxic substances are soluble in
HCl and with Ferric Chloride (FeCl3) they are precipitated out. These precipitates
contain needle-shaped crystals and can be observed microscopically.
D) Test for hydrocyanic acid
Hydrocyanic acid is present as an impurity in synthetic ethyl isothiocyanate, which is
employed to make the flavour of mustard oil more pungent. The method is based on
the reaction of hydrocyanic acid on the picric acid paper, which acquires a red colour
in the presence of that acid.
After learning about the different tests for assessment of the quality of fats and oils,
let us now apply this knowledge in assessing the quality of a given sample of fats and
oils in experiments 1-5.
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Fats and Oils
ACTIVITY
1
DETERMINATION OF MOISTURE CONTENT
Aim: To determine the moisture content in the given sample of oil/fat.
Date: ………….
Objectives
After undertaking this activity, you will be able to:
•
assess the moisture content in the given sample of oil/fat, and
•
check the given sample for conformance to the standard for moisture content.
Principle
Moisture is determined by drying the weighed test material in an air oven. The loss in
weight due to evaporation is accepted as the moisture content. However, it has been
observed that materials in the air oven method shall also entail loss of volatile and
thermo-sensitive constituents, as well as, moisture. Also in case of oils, it is seen that
highly unsaturated oils such as fish oils or linseed oil may oxidize under the test
condition and an increase in weight rather than a weight loss may be recorded.
Lauric acids and other short chain fatty acids slowly volatilizes under the test
condition as their chains are short. Spattering also produces errors as it leads to the
loss of sample during drying.
Several methods such as Dean and Stark method, Karl Fisher method are available
for estimating the moisture content of an oil. However, for our estimation in
laboratories, using the basic infrastructure, we will be conducting the moisture
content with the air oven method.
Materials Required
Sample of oil/fat
Moisture dish-made of porcelain, silica, glass or aluminium
Oven-electric, maintained at 105 ± 1°C.
Desiccator
Weighing balance
Procedure
Carry out the experiment following the procedure enumerated herewith:
1) Weigh accurately about 10 to 15 g of the sample in the moisture dish, previously
dried in the oven and weighed.
2) Place the dish in the oven maintained at 105 ± 1°C for 1 hour.
3) Cool in the dessicator and weigh.
4) Repeat the process of drying, cooling and weighing at 30 minutes intervals until
the difference between two consecutive weighings is less than one milligram.
5) Record the lowest weight.
6) Calculate the moisture content using the formula given herewith.
Calculations
Moisture percent by weight =
100(W1 − W2)
W1 − W
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where,
W1 = weight in g of the dish with the material before drying
W2 = weight in g of the dish with the material after drying to constant weight, and
W
= weight in g of the empty dish.
Precautions
1) The oven-dried sample should not be kept in open but in the dessicator before
weighing.
2) The process of drying should be repeated till the difference in the weighings
should be less than 1 mg.
3) The oven temperature should be regulated throughout the process of drying.
Findings
Record your findings in the format given herewith:
W
= ………………. g
W1 = ………………. g
W2 = ………………. g
Now calculate the moisture content using the formula given above.
Calculations
Moisture % by weight =
Inference
The given sample of oil has ………………… % moisture by weight. The maximum
limit for the moisture content according to PFA, is ………………. % by weight.
Conclusions
(Comment on % moisture content of given sample with respect to PFA)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
……………………………….
Counsellor Signature
70
Fats and Oils
ACTIVITY
1
DETERMINATION OF IMPURITIES
Aim: To determine the impurities in the given sample of oil.
Date: ………….
Objectives
After conducting this activity, you will be able to:
•
•
•
determine impurities such as total dirt and organic dirt in the given sample of oil,
differentiate between total dirt and organic dirt, and
check whether any given samples of oils/fats conforms to the standard.
Principle
As discussed in sub-section 4.4.3, total impurities can be regarded as total dirt and
organic dirt.
The materials required and the procedure for determination of total dirt and organic
dirt is presented separately next.
A)
For Determination of Total Dirt
Materials Required
Sample of Oil/fat
Oven-electric, maintained at 100 ± 1°C.
Dessicator
Weighing balance
Filter paper
Procedure
Carry out the experiment following the procedure enumerated herewith:
1) Take 30-50 g of oil or fat at a temperature below 60ºC.
2) Filter through a filter paper previously dried in the oven at 105ºC and
weighed.
3) Extract the filter paper containing the impurities with light petroleum ether
of grade (boiling pt. 40ºC – 60ºC). In this step, basically pour the ether
onto the filter paper.
4) After complete extraction, dry the filter paper and its contents in the oven
at 98º C-100ºC till a constant weight.
5) Calculate the percentage of total dirt as:
Total dirt, percent by weight =
100(W2 − W)
g
where,
W2 = weight in g of the filter paper with dirt.
W
= weight in g of the filter paper
g
= weight in g of the oil/fat taken for analysis
B) For Determination of Organic Dirt
Materials Required
Sample of oil/fat
Oven – electric, maintained at 100 ± 1°C.
Flat-bottom dish – of stainless steel, porcelain, silica or platinum
Muffle Furnace maintained at 550 ± 10°C
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Desiccator
Weighing balance
Filter paper
Whatman filter paper no. 42 or its equivalent
Procedure
Carry out the experiment following the procedure enumerated herewith:
1) Take 30-50 g of oil or fat at a temperature below 60°C.
2) Filter through the whatman filter paper previously dried in the oven at 105°C.
3) Extract the filter paper containing the impurities with light petroleum ether.
4) After complete extraction, dry the filter paper and contents in the oven at
98°C-100°C.
5) Keep the filter paper in a tared/previously weighed dish.
6) Ignite in a muffle furnace at 550 ± 10°C for one hour.
7) Cool in the desiccator and weigh.
8) Heat the dish again at 550 ± 10°C for 30 minutes, cool in the dessicator and
weigh.
9) Repeat this process of heating for 30 minutes, cooling and weighing until the
difference between two successive weighing is less than one milligram.
Record the lowest weight.
10) Calculate the total organic dirt using the formula given herewith.
Calculations
Total organic dirt, percent by weight =
100(W2 − W)
g
where,
W2 = weight in g of the dish with filter paper with dirt
W
= weight in g of the empty dish
g
= weight in g of the oil/fat taken for analysis
Findings
Record your findings in the format given herewith:
Total Dirt
W2 (weight in g of the dish
with filter paper with dirt)
W (weight in g of the empty
dish)
g
(weight in g of the oil/fat
taken for analysis)
Calculations
72
Organic dirt
Now using the formula given above calculate the following:
Fats and Oils
Total dirt, percent by weight =
Total organic dirt, percent by weight =
Inference
The total dirt percent, present in the given sample is…………………… .
Total organic dirt, percent by weight present in the given sample is ………………. .
Conclusions
(Comment on the total dirt and organic dirt % in the given sample with respect to the
standard).
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
…………………………….
Counsellor Signature
VITY
3
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DETERMINATION OF ACID VALUE AND FREE FATTY
ACIDS
Date: ………….
Aim: To determine the acid value and free fatty acids in the given sample of oil/fat.
Objectives
This activity will help you to:
• know the acidity in given sample of fat/oil, and
• determine the free fatty acid composition in the sample provided for analysis.
Principle
The acid value is determined by directly titrating the material in an alcoholic medium
with aqueous sodium or potassium hydroxide solution. Free fatty acid is calculated as
oleic, lauric, ricinoleic or palmitic acids (refer to section 4.2 of this practical).
The materials required and the procedure for the determination of acid value and free
fatty acid is given herewith.
A)
For Acid Value
Materials Required
Sample of oil/fats namely any refined oil or hydrogenated fat.
Reagents - ethyl alcohol (95%), phenolphthalein indicator solution, standard
aqueous sodium or potassium hydroxide solution (0.1 N or 0.5 N)
Pipette (10 ml)
Conical flask
Procedure
Carry out the experiment following the procedure given herewith:
1) Mix the oil or melted fat thoroughly before weighing.
2) Weigh accurately a suitable quantity of the cooled oil/fat in a 200 ml
conical flask.
3) Add 50-100 ml of the freshly neutralized hot ethyl alcohol (i.e ethyl
alcohol with pH 7).
4) Boil the mixture for about 5 minutes and titrate while as hot as possible
with the standard aqueous alkali solution shaking the solution vigorously
during titration. Continue the titration till the solution turns pink, which is
the end point.
5) Calculate the acid value as per the formula given herewith.
Acid value =
56.1VN
W
where,
V = volume in ml of the standard solution used for titration
N = normality of the standard solution used
W = weight in g of the material taken for the test
B)
Free Fatty Acids
The acidity is frequently expressed as the percentage of free fatty acids present in the
sample.
Materials Required
74
Materials required are the same as above. List down the materials you would require
here.
Fats and Oils
Procedure
Procedure for carrying out the free fatty acids in the given sample is same as that for
acid value determination. Write down the procedure as you conduct the experiment in
the space given herewith.
Calculations
The calculations in terms of different fatty acids are as follows:
Free fatty acids, in terms of
Oleic acid, percent by weight
28.2 VN
=
W
Free fatty acids, in terms of
Lauric acid, percent by weight
20.0 VN
=
W
Free fatty acids, in terms of
Ricinoleic acid, percent by weight =
29.8 VN
W
Free fatty acids, in terms of
palmitic acid, percent by weight =
25.6 VN
W
where,
V = volume in ml of the standard solution used for titration
N = normality of the standard solution used
W = weight in g of the material taken for the test
Results and Observations
Now record your findings for the acid value and the free fatty acid test in the format
given herewith
S. No.
Initial reading
Final reading
Difference
Pilot
1
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2
3
Titre value = ……………(V)
Volume of standard solution used (V) = …………… ml
Weight of the oil taken for analysis = …………… g
Normality of standard NaOH|KOH used = ……………
Now write the formula and calculate the following:
a) Acid Value =
b) Free fatty acids, in terms of
Oleic acid, percent by weight
c) Free fatty acids, in terms of
Lauric acid, percent by weight
=
=
d) Free fatty acids, in terms of
Ricinoleic acid, percent by weight =
e) Free fatty acids, in terms of
Palmitic acid, percent by weight =
76
Inference
Fats and Oils
Acid value, percent by weight calculated in the given sample of oil is………………..
Free fatty acid, percent by weight :
As lauric acid ……………….
As palmitic acid…………….
As ricinoleic acid………….
As oleic acid…………….
Conclusion
(Comment on the acid value and free fatty acids of the given sample of oil/fat)
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
Submit the activity for evaluation.
………………………………
Counsellor Signature
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ACTIVITY
4
DETERMINATION OF PEROXIDE VALUE
Date: ………….
Aim: To determine the peroxide value in the given sample of fat or oil.
Objectives
After undertaking this activity, you will be able to:
• determine the peroxide value in a given sample of fats/oils, and
• check whether any given samples of oils/fats conforms to the standard.
Principle
The peroxide value is a measure of the peroxides contained in a sample of fat
expressed as milli-equivalents of peroxide per 1000 grams of the material.
The material in an acetic acid-chloroform medium, is treated with an aqueous
solution of potassium iodide. The liberated iodine is titrated with the standard sodium
thiosulphate solution.
Materials Required
Reagents
Acetic acid-chloroform solution - Mix three parts by volume of glacial acetic acid
with 2 parts by volume of chloroform
Saturated potassium iodide solution
Sodium thiosulphate solution- 0.1 N
Starch solution (1%)
Apparatus
Pipette 1ml capacity
Conical flask
Procedure
Carry out the experiment following the procedure given herewith:
1) Weigh approximately 5 g of the sample of fat in a 250 ml conical flask.
2) Add 30 ml of the acetic acid-chloroform solution.
3) Swirl flask until the sample is dissolved.
4) Add 0.5 ml of the saturated potassium iodide solution.
5) Allow the flask to stand exactly one minute with occasional shaking and then add
30 ml distilled water.
6) Titrate with 0.1 N sodium thiosulphate solution with constant and vigorous
shaking.
7) Continue the titration until the yellow colour almost disappears.
8) Add 0.5 ml of the starch solution and continue the titration until the blue colour
just disappears.
9) Conduct a blank determination of the process in the same manner as described in
steps 2-8. Here, we start with acetic acid- chloroform solution only. No fat
sample is added.
10) Calculate the peroxide value based on the formula given herewith:
Calculations
Peroxide value as milli-equivalents per 1000 g of sample =
where,
78
(S − B) × N × 1000
g
S = volume in ml of sodium thiosulphate solution used up by the sample.
B = volume in ml of the sodium thiosulphate used up in blank determination.
N = normality of sodium thiosulphate solution.
and g is the weight in gram of the sample.
Fats and Oils
Results and Observations
Weight of the sample taken for the test = …………………..
Volume of acetic acid-chloroform solution added = …………………..
Addition of saturated KI solution = …………………..
Record your observations of the titration performed in the table given herewith.
Titre value
Blank (B)
Sample (S)
1.
2.
3.
Final reading
S= …………………..
B= …………………..
N= …………………..
Weight of the sample = …………………..
Now calculate the peroxide value putting in the values you have written above. But
first write the formulae.
Inference
Peroxide value in the given sample is …………………..
The sample of oil/fat is …………… (conforming/non-conforming) to the
specifications for peroxide value.
Conclusion
(Comment on the peroxide value of the given sample with respect to specifications)
Submit the activity for evaluation.
……………………………….
Counsellor Signature
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ACTIVITY
5
PURITY TESTS OF OILS/FATS
Date: ………….
Aim: To detect the presence for sesame oil, linseed oil, argemone oil, mineral oil and
hydrocyanic acid.
Objectives
After undertaking this activity, you will be able to:
• discuss the various adulterants in oils/fats, and
• qualitatively determine their presence in the given samples.
Principle
You are already aware of the principles involved in the detection of adulterants.
Refer to sub-section 4.4.6. Write the principle involved for each oil in the space
provided.
Sesame oil
Linseed oil
Argemone oil
Mineral oil
Hydrocyanic acid
80
Materials Required
Fats and Oils
1) One sample of oil (sample 1) and one sample of fat (sample 2)
2) Hydrochloric acid - fuming, relative density 1.19
3) Furfural solution - 2 % solution of furfural distilled not earlier than 24 hours. The
reagent is stable up to 3 months if kept in the refrigerator
4) Chloroform
5) Liquid bromine
6) Rectified spirit
7) Ether
8) FeCl3 solution - 10%
9) Alcoholic caustic potash solution- 0.5 N
10) Picric acid paper – soak a filter paper (Whatman no. 1 or equivalent) in a
saturated aqueous solution of picric acid, draining excess liquid and drying the
dyed paper in air. The paper should be prepared freshly before use.
11) Tartaric acid solution - 10 % (m/v)
12) Sodium carbonate solution - 5% (m/v)
Procedure
Now, let us start with the procedure for the detection of the aforesaid adulterants in
the given sample of oils/fats. Carry out the experiment following the procedure given
herewith:
Sesame oil
1.
2.
Take 5 ml of
sample in a
stoppered test tube.
Add 5 ml HCl and
0.4 ml furfural
solution.
3.
Shake vigorously
4.
Allow the mixture
to separate.
5.
Pink or red colour
in the acid layer
indicates the
presence of
sesame oil.
Linseed oil
1.
Take 1 ml of oil
in a dry test tube.
2.
Add 5 ml of
chloroform.
3.
Add 1 ml of
bromine
dropwise till the
mixture is deep
red in colour.
4.
Add 1.5 ml of
rectified spirit
shaking the
mixture till
precipitate
formed gets
dissolved.
5.
Add 10 ml of
ether and place
the tube in ice
water bath for 30
minutes.
6.
Appearance of
precipitate
indicates the
presence of
linseed oil.
Argemone oil
1.
Take 5 ml of oil
and heat it with
5 ml conc. HCl on
a water bath
2.
Add 5 ml of FeCl3
solution slowly.
3.
Orange red
precipitates in the
acid layer indicates
the presence of
argemone oil.
4.
For confirmation
the precipitate
should be observed
microscopically for
the presence of
needle shaped
crystals.
Mineral oil
1.
2.
3.
Take 0.1 ml of
oil in a wide
test tube and
add 2.2 ml of
alcoholic
KOH.
Heat it on
boiling water
bath for 5 min
and add 25 ml
of hot distilled
water and mix.
The presence
of mineral oil
is indicated by
the immediate
turbidity in the
solution.
Hydrocyanic acid
1.
Pour about 30 ml
of oil in a conical
flask.
2.
Add 15 ml of
tartaric acid
solution and mix.
3.
Stopper the flask
with a cork from
which hangs the
picric acid paper
wetted with a
drop of sodium
carbonate
solution.
4.
Place the flask
on a hot water
bath for 30-40
minutes.
5.
The picric acid
paper acquires
red colour in the
presence of
hydrocyanic
acid.
Now, as you have finished with the procedure let us again go through the
confirmatory tests. (Fill in the blanks)
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Principles of Food
Science
Sesame oil - detection of …………… colour in the acid layer. However, if the colour
disappears after a few seconds it is absent.
Linseed oil - appearance of …………… in the tube containing oil, chloroform,
rectified spirit, liquid bromine and ether.
Argemone oil - presence of …………… ppt. on addition of FeCl3. The ppt. are
having …………… crystals when observed microscopically.
Mineral oil - …………… in the solution of alcoholic KOH and oil indicates the
presence of mineral oil.
Hydrocyanic acid- …………… coloured spot on the picric acid solution indicates the
presence of hydrocyanic acid.
Observations
Write the observations in the format given herewith.
Presence of adulterants
Sesame oil
Linseed oil
Argemone oil
Mineral oil
Hydrocyanic acid
Inference
82
Sample 1- observations
Sample 2 - observations
The given samples of oil/fats contains the following adulterants.
Fats and Oils
Conclusion
(Comment on the quality of oil/fat according to the presence/absence of any
adulterant).
…………………………………………………………………………………………..
…………………………………………………………………………………………..
…………………………………………………………………………………………..
…………………………………………………………………………………………..
…………………………………………………………………………………………..
…………………………………………………………………………………………..
Submit the activity for evaluation.
……………………………
Counsellor Signature
83
PRACTICAL 5
EVALUATION OF MILK
SAMPLES
Structure
5.1
5.2
5.3
Introduction
Milk – Quality Specifications
Basic Tests for Milk Analysis
5.3.1
5.3.2
5.3.3
5.3.4
5.3.5
5.3.6
5.3.7
5.3.8
Taste, Flavour and Appearance
Milk pH
Alcohol Test
Presence of Additives
Fat Content in Milk
Total Solids in Milk
Solid Non-Fat (SNF)
Proteins in Milk
Activity 1: Determination of Physical Characteristics and Presence of any Additives
Activity 2: Determination of the Fat Content
Activity 3: Determination of the Percentage of Total Solids
Activity 4: Determination of the Solid Non-Fat (SNF) Percentage
Activity 5: Determination of the Protein Content
5.1
INTRODUCTION
Milk is one of the most common articles of food throughout the world. It is regarded
as a complete food. Why? Simply, because it contains protein, fat, carbohydrates, all
the known vitamins, various minerals and all the food ingredients considered
essential for sustaining life and maintaining health. The protein of milk is of the
highest biological value and it contains all the amino acids essential for body building
and repair of body cells.
Various tests are available for milk composition and milk quality analysis. Practical 5
focus on these tests.
Objectives
After completing this practical and the activity given herewith, you will be able to:
•
•
•
•
•
5.2
enlist the different types of milk available based on their fat percentages,
distinguish between synthetic milk and pure milk,
determine the total fat and protein content in a given sample of milk,
detect the presence of additives in a sample of milk, and
detect the total solids and solids not-fat percentage in a sample of milk.
MILK – QUALITY SPECIFICATIONS
Milk is a whole, clean, fresh lacteal secretion obtained by complete milking of one or
more healthy milch animals. Milking is not done 15 days before or 5 days after
calving or such periods as may be necessary to render the milk practically colostrum
free containing minimum prescribed percentage of milk fat and SNF (solids non-fat).
The components of milk are water, which is around 87 per cent, fat, present in the
form of an emulsion, protein (3.5%), lactose, vitamins and minerals. Milk is
classified on the basis of SNF and fat content. The PFA standards prescribed for milk
is given in Table 5.1.
84
Evaluation of Milk
Samples
Table 5.1: PFA standards prescribed for milk
Types of milk
SNF (percentage)
Fat (percentage)
Skimmed milk
8.7 minimum
0.5 maximum
Double toned milk
9.0 minimum
1.5 maximum
Toned milk
8.5 minimum
3.0 maximum
Standard milk
8.5 minimum
4.5
Full cream
9.0 minimum
6.0
The quality of milk and milk products is rigorously controlled by laboratory tests at
each stage till the milk is delivered to the final consumer. Thus, some tests are
regarded as the platform tests of milk, which results in acceptance, or rejection of the
milk samples collected. Milk is evaluated for its fat, milk solids non-fat and various
adulterants in milk. The tests can be regarded as physical tests, chemical tests and
microbiological analysis. In this chapter we will limit ourselves to the physical and
chemical tests for milk analysis. We shall study about the microbiological analysis of
milk in the Food Microbiology and Safety Practical (Course MFNL-003).
Let us start with the basic tests first.
5.3
BASIC TESTS FOR MILK ANALYSIS
The Federation R&D has developed these tests stepwise and these should be done in
the same sequence along with the blank, good milk. Let us learn about these tests.
5.3.1 Taste Flavour and Appearance
Milk should have its own mild sweet flavour. A soapy or chemical flavour and slight
pale colour or extra white colour may give indication regarding adulteration. Rancid
flavours in milk are also easily detectable through perception of smell.
5.3.2 Milk pH
Milk has a pH between 6.6 to 6.8. The pH of the given sample of milk can be tested
by pH strip prepared with phenol red, which gives a change in colour exactly at pH
7.0. Thus this strip is sensitive to even slight levels of neutralization.
5.3.3 Alcohol Test
Alcohol test is based on the principle of curdling of milk in presence of alcohol. This
forms the principle for testing of synthetic milk, which is composed of neutralizers,
stabilizers and detergents.
Take 0.5 ml of milk sample in a test tube along with a blank (sample of a good milk).
Add to each tube 0.5 ml of 95% alcohol, mix, heat and observe for clotting.
5.3.4 Presence of Additives
The additives such as starch, urea, sugar and soda are added to milk to maintain its
colour, flavour, sweetness and pH. For the analysis of these adulterants, standard
methods are used. These are highlighted herewith:
For Starch: Iodine test is used.
For Soda: Rosalic acid test is used for determination of added soda.
For Sugar: Resorcinol test is used for determination of sugar.
For Urea: Dimethyl amino benzaldehyde test is used for urea determination.
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Principles of Food
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The procedure for detecting the presence of these additives is presented in Table 5.2.
Table 5.2: Procedure for detecting the presence of starch, soda, starch, urea in a sample
of milk
Starch
Soda
1.
Take 1 ml of the
milk sample
1.
Take 5 ml of
milk sample
2.
Add 0.5 ml of
iodine solution
2.
Add equal
quantities of
rosalic acid
solution.
3.
Blue colour in
the solution
indicates starch
aduteration
3.
If solution
turns pink it
indicates that
soda has been
added.
Sugar
1.
Take 0.1 ml of
the milk
sample
2.
Add 0.2 ml of
resorcinol
solution
3.
Boil for 30
seconds
4.
The colour
change to pink
indicates the
presence of
added sugar
Urea
1.
Take 0.5 ml of the
test milk sample
and one control
sample in each test
tube
2.
Add 0.5 ml of the
prepared DAMB
solution in each
test tube
3.
Observe for the
colour changes.
4.
Deep yellow
indicates the
presence of added
urea
We shall apply these procedures in experiment 1 to determine the presence of these
additives in a given sample of milk.
Next, let us get to know about the different tests used to determine the milk
composition. We start with the procedures for fat content in milk.
5.3.5 Fat Content in Milk
The fat content in milk can be determined through various procedures as:
Direct determination of fat by extraction with ether – Adam's coil method
•
Separation of fat by acid/ alkali treatment and its subsequent removal by ether–
Werner-Schimdt and Gottleib method
•
Separation of fat by chemical means followed by centrifugation – Gerber method
The main principle behind the fat determination is protein precipitation, which is
further dissolved in acid to free fat globules. In some methods, amyl alcohol is also
added to produce difference in the surface tension of fat globules and the supporting
liquid, thus causing the aggregation and separation of fat.
As Gerber method gives fast results, thus, it is used in the dairy plants as a platform
test for checking the quality of milk. In this test, fat is dissolved in hot amyl alcohol
and its separation from heavy acid solution is affected by subjecting the mixture to
centrifuging. In Gerber method, 10 ml of conc. H2SO4 is added into the gerber tube.
1 ml of amyl alcohol is added in this tube. 10.94 ml of the milk sample is added and
the tube is stoppered. The tube is then inverted twice or thrice and shaken briskly to
mix the ingredients. The tube is then centrifuged for 3 min at 1000 rpm to get the
reading of fat in the stem of the tube.
However, as this method is requiring special equipments like gerber tube, as
highlighted in Figure 5.1(a), and milk centrifuge system, we will in this exercise limit
ourselves to the Rose-Gottleib method which is a gravimetric extraction method. A
rose-gottleib tube is illustrated in Figure 5.1(b).
86
Evaluation of Milk
Samples
Figure 5.1: Apparatuses for fat analysis in milk
5.3.6 Total Solids in Milk
Total solids determination is a common procedure in many manufacturing plants
using dairy products. The total solids in milk can be calculated from the specific
gravity and fat percentage from the table wherein lactometer reading is taken at
60° F. Table 5.3 gives the lactometer reading for a given percentage of fat. You can
refer to this table to calculate the total solids in milk.
Besides carrying out the total solids percentage from the indirect method of taking
lactometer reading, a direct method of gravimetric analysis can also be used. This
method involves accurately weighing a few grams of the material and subjecting it to
heat until all moisture has been driven off on a water bath. The dry residue is
weighed, its percentage calculated as total dry solids.
We would be analyzing the total solids percentage in the given sample of milk in
activity 3 of this practical.
5.3.7 Solids Non-Fat (SNF)
Solid non-fat is an important criterion of milk selection for further processing. Milk
solids non-fat would include the nitrogenous substances, milk sugar and mineral
matter.
The determination of solid non-fat is done by taking lactometer reading at 40°C. The
method is fully explained in experiment 4 of this practical. You shall be applying this
procedure to determine the SNF of a given sample of milk.
5.3.8 Proteins in Milk
Milk comprises of casein, lactoalbumins and lactoglobulins. About 82 per cent of the
protein in milk is casein and the remaining proteins are whey proteins, which are
lactoalbumin and lactoglobulin. Casein binds with calcium in milk and forms the
calcium-caseinate complex, which is present in the colloidal form. Acid, rennet,
alcohol and heat can precipitate this complex.
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Principles of Food
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88
Table 5.3: Lactometer reading and the percentage of fat
Lactometer reading at 60ºF (15.6ºC) (Quevenne degrees)
Percentage
of fat
26
27
28
29
3.00
10.10
10.35
10.60
10.85
3.05
10.16
10.41
10.66
3.10
10.22
10.47
3.15
10.28
3.20
30
31
32
33
34
35
36
11.10
11.36
11.61
11.86
12.11
12.36
12.61
10.91
11.17
11.42
11.97
11.92
12.11
12.17
12.68
10.72
10.97
11.23
11.48
11.73
12.04
12.11
12.23
12.74
10.53
10.78
10.03
11.29
11.54
11.79
12.10
12.11
12.29
12.80
10.30
10.59
10.84
10.09
11.35
11.60
11.85
12.16
12.11
12.35
12.86
3.25
10.40
10.65
10.90
10.16
11.41
11.66
11.91
12.22
12.11
12.42
12.92
3.30
10.46
10.71
10.96
10.22
111.47
11.72
11.97
11.81
12.11
12.48
12.98
3.35
10.52
10.77
11.03
11.29
11.53
11.78
12.03
12.28
12.54
12.79
13.04
3.40
10.58
10.83
11.09
11.34
11.59
11.84
12.09
12.34
12.60
12.85
13.10
3.45
10.64
10.89
11.15
11.40
11.65
11.90
12.15
12.40
12.66
12.91
13.16
3.50
10.70
10.95
11.21
11.46
11.71
11.96
12.21
12.46
12.72
12.97
13.22
3.55
10.76
10.02
11.27
11.52
11.77
12.02
12.27
12.52
12.78
13.03
13.28
3.60
10.82
10.08
11.33
11.58
11.83
12.08
12.33
12.58
12.84
13.09
13.34
3.65
10.88
11.14
11.39
11.64
11.89
12.14
12.39
12.64
12.90
13.15
13.40
3.70
10.94
11.20
11.45
11.70
11.95
12.20
12.45
12.70
12.96
13.21
13.46
3.75
11.00
11.26
11.51
11.76
12.01
12.26
12.51
12.76
13.02
13.27
13.52
3.80
11.06
11.32
11.57
11.82
12.07
12.32
12.57
12.82
13.08
13.33
13.58
3.85
11.12
11.38
11.63
11.88
12.13
12.38
12.63
12.88
13.14
13.39
13.64
3.90
11.18
11.44
11.69
11.94
12.19
12.44
12.69
12.94
13.20
13.45
13.70
3.95
11.24
11.50
11.75
12.00
12.25
12.50
12.75
13.00
13.26
13.51
13.77
4.00
11.30
11.56
11.81
12.06
12.31
12.56
12.81
13.06
13.32
13.57
13.83
4.05
11.36
11.62
11.87
12.12
12.37
12.62
12.87
13.12
13.38
13.63
13.89
4.10
11.42
11.68
11.93
12.18
12.43
12.68
12.93
13.18
13.44
13.69
13.95
4.15
11.48
11.74
11.99
12.24
12.49
12.74
12.99
13.25
13.50
13.76
14.01
4.20
11.54
11.80
12.05
12.30
12.55
12.80
13.05
13.31
13.56
13.82
14.01
4.25
11.60
11.86
12.11
12.36
12.61
12.86
13.12
13.37
13.62
13.88
14.13
4.30
11.66
11.92
12.17
12.42
12.67
12.92
13.18
13.43
13.68
13.94
14.19
4.35
11.72
11.98
12.23
12.48
12.73
12.98
13.24
13.49
13.74
14.00
14.25
4.40
11.78
12.04
12.29
12.54
12.79
13.04
13.30
13.55
13.80
14.06
14.31
4.45
11.84
12.10
12.35
12.60
12.85
13.10
13.36
13.61
13.86
14.12
14.37
4.50
11.90
12.16
12.41
12.66
12.91
13.16
13.42
13.67
13.92
14.18
14.43
4.55
11.97
12.22
12.47
12.72
12.97
13.22
13.48
13.73
13.98
14.24
14.49
4.60
12.03
12.28
12.53
12.78
13.03
13.28
13.54
13.79
14.04
14.30
14.55
4.65
12.09
12.34
12.59
12.84
13.09
13.34
13.60
13.85
14.10
14.36
14.61
4.70
12.15
12.40
12.65
12.90
13.15
13.40
13.66
13.91
14.16
14.42
14.67
4.75
12.21
12.46
12.71
12.96
13.21
13.46
13.72
13.97
14.22
14.48
14.73
4.80
12.27
12.52
12.77
13.02
13.27
13.52
13.78
14.03
14.28
14.54
14.79
4.85
12.33
12.58
12.83
13.08
13.33
13.58
13.84
14.09
14.34
14.60
14.85
4.90
12.39
12.64
12.89
13.14
13.39
13.64
13.90
14.15
14.40
14.66
14.91
4.95
12.45
12.70
12.95
13.20
13.45
13.70
13.96
14.21
14.46
14.72
14.97
5.00
12.51
12.76
13.01
13.26
13.51
13.76
14.02
14.27
14.52
14.78
15.03
The proteins in milk are determined by the Kjeldahl procedure, which is defined as
the amount of nitrogen experimentally found and multiplied by an approximate
conversion factor. In this procedure, as you may have already studied about in the
Nutritional Biochemistry practical (Course MFNL-002), the sample of milk is
oxidized in the presence of sulphuric acid and nitrogenous compounds are converted
into ammonium sulphate. Ammonia is liberated by adding an excess of alkali and is
quantitatively distilled into a measured volume of standard hydrochloric acid or
sulphuric acid. The acid not neutralized by ammonia is back-titrated with standard
alkali. The conversion factor used for milk and milk products as given by BIS is 6.38.
Evaluation of Milk
Samples
Although Kjeldahl method gives the accurate estimation milk proteins but as the
digestion of milk poses the problem at the laboratory scale thus we would carry out
the estimation of milk proteins through Pyne's method or aldehyde number method.
This method gives the approximate estimation of the total protein present in milk and
is also used as the platform test.
Let us now start with the various tests involved in the evaluation of the given sample
of milk.
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Principles of Food
Science
ACTIVITY
1
Date: ………….
DETERMINATION OF THE PHYSICAL
CHARACTERISTICS AND PRESENCE OF ANY
ADDITIVES
Aim: To determine the physical characteristics and presence of any additives in the
given samples of milk.
Objectives
After undertaking this activity, you will be able to:
• identify the physical characteristics of milk,
• determine any additives present in milk, and
• distinguish between synthetic milk and pure milk.
Principle
The principle is discussed in sub-section 5.3.4 of this practical. We suggest you look
up the sub-section once again and write the principle here in the space provided.
Materials Required
1)
2)
3)
4)
5)
Sample of milk
Iodine solution
0.01% alcoholic solution of rosalic acid
Resorcinol solution (0.05 g resorcinol in 100 ml of dilute HCl (1:2)
DAMB solution- dissolve 0.4 g of p-dimethyl amino benzaldehyde in 250 ml
alcohol and add 23 ml of conc. HCl
6) pH strip prepared with phenol red
7) 95% alcohol
Procedure
You may recall studying about the procedure for determining the physical
characteristics in sub-section 5.3.4 earlier in this practical. Write the procedure for
carrying out the adulteration tests in the format given herewith:
Starch
90
Soda
Sugar
Urea
Next carry out the pH test and alcohol test as indicated in the sub-section 5.3.2 and
5.3.3 earlier.
Evaluation of Milk
Samples
Observations
Based on the experiment you have just conducted, write your observations in the
format given herewith:
Characteristics/adulterants
Sample
Taste, flavour and appearance
pH
Alcohol test
Presence of starch
Presence of soda
Presence of sugar
Presence of urea
Inference
The given samples of milk were found to be of ………….. quality on the parameters
of taste, flavour and appearance and pH. The samples tested for presence of additives
gave the following results:
Additives
Sample
Starch
Soda
Sugar
Urea
Conclusion
(Comment regarding the acceptability of the sample)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
……………………………..
Counsellor Signature
91
Principles of Food
Science
ACTIVITY
2
DETERMINATION OF THE FAT CONTENT
Date: ………….
Aim: To determine the fat content in the given sample of milk.
Objectives
After undertaking this activity, you will be able to:
•
explain the technique of determination of the total fat content in the samples of
milk and milk products, and
•
differentiate between the different types of milk available varying in their fat
percentages.
Materials Required
Samples of milk (toned/double toned and full cream milk)
The rose gottlieb tube/ separating funnels
Tared beakers
Ammonia
Diethyl ether
Petroleum ether (40-60ºC)
95% alcohol
Air-oven maintained at 100ºC
Principle
The principle of the fat extraction has been discussed in sub-section 3.3.5 earlier in
this practical. Recapitulate what you learnt and write down the principle here in the
space provided.
Procedure
Now carry out the experiment step-by-step as enumerated herewith:
1) Take 10 ml of the milk sample in the rose-gottlieb tube. Alternatively, you can
take the contents in a beaker.
2) Add 2 ml of ammonia.
3) Cork the rose-gottlieb tube and mix the contents by shaking, with slight warming,
until the contents present an entirely homogenous appearance and are free from
flakes of protein. In case the beaker is used, mix contents with a glass rod and
pour contents into the separating funnel.
4) Add 10 ml of 95 per cent alcohol with further shaking.
5) Now add 18 ml of ethyl ether and mix the contents of the tube/separating funnel
thoroughly by repeated inversions.
6) Add 18 ml of petroleum ether and mix again.
92
7) Let it stand for a few minutes till the separation of the ether solution containing
fat is obtained.
Evaluation of Milk
Samples
8) Transfer the ether layer in a small tared/ previously weighed beaker by means of
wash bottle tube. Alternatively, do the mixing of the contents in a separating
funnel and separate the ether layer in a tared beaker.
9) Repeat the extraction twice with small quantities of mixture of equal parts of
ethyl ether and petroleum ether and add to the main volume of ether solution
(already collected in the tared beaker).
10) Evaporate the ether by immersing the beaker in hot water bath.
11) Heat it in the air-oven at 100 ºC. Cool and weigh the beaker.
12) Calculate the fat content as given below.
Calculations
Total fat, percent by weight =
100(W1 − W)
g
where,
W1 = weight in g of the beaker with the fat
W = weight in g of the empty beaker
g = weight in g of the milk sample taken for analysis
Results/ Findings
Record you observations/ findings here and calculate the total fat percent.
Milk sample =
Weight of the milk sample used for analysis (g) = …………….. .
Weight of the beaker (W) = ……………...
The final weight of the beaker containing fat (W1) = …………….. .
Total fat percent by weight can be calculated as:
Inference
The given sample of milk is having ---------- fat percent by weight and thus can be
classified as ----------toned/ double toned/ skim/ full cream milk.
Conclusion
(Comment regarding the acceptability of the sample)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
…………………………….
Counsellor Signature
93
Principles of Food
Science
ACTIVITY
3
Date: ………….
DETERMINATION OF THE PERCENTAGE OF TOTAL
SOLIDS
Aim: To determine the percentage of total solids in the given samples of milk.
Objectives
After undertaking this activity, you will be able to:
• explain the technique of determination of the total solids in the samples of milk
and milk products, and
• analyze the percentage total solids in different types of milk available.
Materials Required
Two samples of milk (toned/double toned and full cream)
Shallow flat bottom dishes of aluminium alloy, nickel, stainless steel, porcelain/silica
about 7-8 cm in diameter and 1.5 cm in height.
Air oven maintained at temperature 100°C
Weighing balance
Principle
The knowledge of the fat content and the specific gravity of the milk can determine
total solids in milk. The percentage of total solids can be measured by the application
of a simple formula as given below:
T = 0.25 G + 1.2 F + 0.14
where,
T represents the percentage of total solids
G represents the specific gravity (in degrees)
F represents the percentage of fat
The gravimetric method as discussed in sub-section 5.3.6 earlier in this practical
would be used in this exercise for the determination of total solids. Write down the
principle of gravimetric method here in the space provided:
Procedure
Now carry out the experiment step-by-step as enumerated herewith:
1) Weigh accurately the clean, dry empty dish with the lid.
2) Pipette into the dish about 5 ml of the prepared sample of milk and weigh quickly
with the lid on the dish.
3) Place the dish uncovered on a boiling water bath.
4) Keep the base of the dish horizontal to promote uniform drying and protect it
from direct contact with the metal of the water bath.
5) After at least 30 minutes remove the dish, wipe the bottom and transfer to an air
oven maintained at 100°C ± 2°C.
94
6) At the end of one hour, remove the dish to a dessicator and allow to cool
completely before weighing again.
7) To ensure the constancy of weight, the dish must be replaced in the air-oven for
successive periods of 30 minutes, with intermediate weighing, until two
consecutive weighing differ by less than one milligram.
8) Note the lowest weight.
9) Calculate the total solid percent by weight using the formula given herewith.
Evaluation of Milk
Samples
Calculations
Total solids, percent by weight =
100 × W1
W
where,
W1 = weight in g of the residue after drying.
W = weight in g of the prepared sample taken for test.
Precautions
1) The dish should be kept on a water bath for the evaporation of water.
2) In the oven, do not place the dish near the walls of the oven.
Results/Findings
Record you observations/findings here in the format provided and calculate the total
fat percent.
Milk sample 1
Milk sample 2
Weight of the milk sample used for analysis
Weight of the beaker (W)
The final weight of the beaker containing
residue (W1)
Total solids, percent by weight, can be calculated asSample 1
Sample 2
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Inference
The given sample no.1 is having ---------- total solids percent by weight.
The given sample no.2 is having ---------- total solids percent by weight.
Conclusion
(Comment regarding the acceptability of the sample)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
……………………………….
Counsellor Signature
96
Evaluation of Milk
Samples
DETERMINATION OF THE SOLID NON-FAT (SNF)
PERCENTAGE
Aim: To determine the solids non-fat percentage in the given samples of milk.
ACTIVITY
4
Date: ………….
Objectives
After undertaking this activity, you will be able to:
• explain the technique of determination of the solids not-fat in the samples of
milk,
• check the variations in percentage solids non-fat in various samples of milk, and
• check the given sample for conformance to the standard for SNF content.
Principle
Solid non-fat is an important criterion of milk selection for further processing. Milk
solids non-fat would include the nitrogenous substances, milk sugar and mineral
matter.
The determination of solid non-fat is done by taking Lactometer reading at 40°C.
Also refer to section 5.4
Materials Required
Sample of milk
Lactometer
The rose gottlieb tube/ separating funnels
Tared beakers
Ammonia
Diethyl ether
Petroleum ether (40-60ºC)
95% alcohol
Air-oven maintained at 100ºC
Weighing balance
Procedure
Determine the fat content in the given sample of milk as explained in experiment 2 of
this practical.
For taking the Lactometer reading, carry out the following steps:
1) Warm the milk sample to 40°C.
2) Mix the contents by rotating and inverting the bottle, taking care to avoid air
bubbles. Alternatively, mix the contents in a beaker.
3) Pour about 50 ml of milk in the measuring cylinder.
4) Insert the lactometer gently to wet the stem not more than a short length, about
3 mm beyond the position of equilibrium.
5) Note the reading regarding top of the meniscus on the stem.
6) Calculate the SNF percent using the formula given herewith:
Calculations
SNF, percent
= Lactometer reading + 0.2 F + 0.29
where,
F = Fat percent.
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Precautions
1) Milk should be mixed gently and not vigorously. Vigorous shaking causes the
milk to froth which leads to a fallacious reading.
2) Lactometer should float freely and not touch the sides of the cylinder.
Results/Findings
Record your observations/ findings in the format given herewith and calculate the
total fat percent.
Milk sample 1
Milk sample 2
Lactometer reading
Fat percent
SNF percent by weight can be calculated asLactometer reading + 0.2F + 0.29
Sample 1: SNF per cent =
Sample 2: SNF per cent =
Inference
The given sample no.1 is having ---------- SNF content and ----------- fat percent and
thus can be classified as ---------- (toned/ double toned/ skim/ full cream milk).
The given sample no.2 is having ---------- SNF content and ----------- fat percent and
thus can be classified as ---------- (toned/ double toned/ skim/ full cream milk).
Conclusion
(Comment regarding the acceptability of the sample)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
………………………………
Counsellor Signature
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Evaluation of Milk
Samples
ACTIVITY
5
DETERMINATION OF THE PROTEIN CONTENT
Aim: To determine the protein content in the given sample of milk.
Date: ………….
Objectives
After undertaking this activity, you will be able to:
• explain the technique of determination of protein content in the given samples of
milk,
• discuss the various factors in determination of proteins in milk, and
• check the given sample for conformance to the standard for protein content.
Principle
Pyne's method or aldehyde number method gives the approximate estimation of the
total protein present in milk and is also used as the platform test. Milk proteins
contain amino groups which react with formalin and thereby increasing its acidity
due to formation of an NH3+ ion and lowers the alkalinity of the – NH2 group
CH-NH2
COOH
Amino acid
H
+
C=O
H
Formaldehyde
H2N+– CH2 – COO –
Aldehyde number is expressed as the amount of 1N NaOH required to neutralize the
acidity generated in 1 lt. of milk through the addition of 2 ml of formaldehyde
(HCHO).
Materials Required
1)
2)
3)
4)
5)
Sample of milk
Formaldehyde – 40% concentrated and neutral to phenolphthalein
Phenolphthalein indicator solution
Potassium oxalate solution- saturated and neutral to phenolphthalein
Standard NaOH solution (0.1 N)
Procedure
Now carry out the experiment step-by-step as enumerated herewith:
1) Take 10 gram of sample accurately weighed in a conical flask.
2) Add 1 ml of phenolphthalein indicator.
3) Add 0.4 ml of saturated potassium oxalate solution.
4) Set aside for 2 minutes.
5) Titrate against 0.1 N NaOH till end point (presence of light pink colour)
6) Add 2 ml formaldehyde.
7) Titrate against 0.1 N NaOH till end point.
8) Calculate the protein percent using the formula given herewith.
Calculations
Protein percent is calculated as = Volume of NaOH × 1.7
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Results/ Findings
Record your readings in the observation table given below:
S. No.
Initial reading
Final reading
Difference (v)
Pilot
1
2
3
V = ……………… ml
V= volume of NaOH used
The percentage protein found in the given sample of milk is calculated as:
Volume of NaOH used = ……………. ml.
Protein percentage is = Valume of NaOH × 1.7
Now calculate the protial percentage in the space provided:
Inference
The given sample of milk had ………………… percentage of proteins.
Conclusion
(Comment regarding the acceptability of the sample)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
……………………………….
Counsellor Signature
100
PRACTICAL 6
SENSORY EVALUATION OF
FOODS
Sensory Evaluation of
Foods
Structure
6.1 Introduction
6.2 What is Sensory Evaluation?
6.3 Various Tests Involved in the Sensory Evaluation of Foods
6.4 Techniques of Sensory Evaluation
6.5 Requirements for the Evaluation Process
6.6 Taste Sensitivity
6.7 Descriptive Analysis
6.8 Product Descriptors
Activity 1: Determination of the Taste Threshold for the Different Sensations –
Sweet, Salty and Sour
Activity 2: Conduct a Descriptive Analysis of the Given Sample of White Bread on
the Basis of its Sensory Attributes.
6.1
INTRODUCTION
In Unit 8, in the theory course (MFN-008), you may recall studying that when the
quality of a food product is assessed by means of human sensory organs, the
evaluation is said to be ‘sensory’ or ‘subjective’ or ‘organoleptic’. Sensory quality is
a combination of different senses of perception coming into play in choosing and
eating a food. This practical will focus on the sensory evaluation of foods. We will
see how the individual threshold for different sensations varies from individual to
individual. We suggest, before you start this practical, look up the quality attributes
of foods as discussed in Unit 8 and also the description on sensory evaluation
presented in Unit 14 in section 14.4 in the course MFN-008.
Objectives
After studying this practical and undertaking the activities included in this practical,
you will be able to:
• perceive about the individual differences existing for taste stimulation, and
• recognize your own threshold and identification level for different taste
stimulations.
6.2
WHAT IS SENSORY EVALUATION?
Foods have several characteristics that require evaluation by sensory methods. The
various food attributes that are judged on the sensory scale are flavour, texture,
aroma and appearance. Every time the food is eaten, the quality is evaluated or the
judgment is made. The reaction of the consumer on the basis of the sensory
perception serves as an endorsement or proof of the product acceptance.
The sensory evaluation of food is carried out on a scientific basis to ascertain the
product formulations or processing techniques that are anticipated to be successful in
the market place. In the research and development process of a product, trained
sensory panelists evaluate the samples and provide guidance in improvement of the
product. This type of testing wherein the scores are determined by individual
decisions based on the use of senses and do not rely on the mechanical devices, is
known as sensory or subjective evaluation. Thus, sensory evaluation has been defined
as a scientific method to evoke, measure, analyze and interpret those responses to
products as perceived through the senses of sight, smell, touch, taste and hearing
(Stone and Sidel, 1995).
Sensory receptors such as olfactory receptors, taste receptors and visual receptors are
used to study the following attributes of food:
1) Appearance
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2) Taste
3) Flavour
4) Texture
5) Consistency
You may recall studying about these attributes in Unit 8 in the theory course. Here,
let us briefly review these attributes.
1) Appearance
The appearance of a food can be evaluated in terms of colour, surface characteristics
such as smoothness of a surface, dry surface, glossy surface or the exterior
appearance such as lump formation, thickness or thinness, layering etc.
2) Taste
Individuals respond to a product on the basis of their sensory perception and judge
the product quality differently. The auditory sense is the least used in appreciation of
food quality, however, the senses for taste stimulation has a strong influence on the
acceptability of food quality.
Taste is sensed by taste buds, which you may already know by now, are located in
the papillae on the tongue. Taste buds are located in the epithelium and on the parts
of the tongue where the food contacts the most during chewing and swallowing.
Taste sensations which the taste buds register are sweet, salt, sour and bitter. Taste
buds near the tip of the tongue are more sensitive to sweet and salt, those on the sides
to sour and those near the back to bitter, as illustrated in Figure 6.1.
Figure 6.1: Taste buds on tongue
3) Flavour
Flavour is composed of two subcategories, which are taste and odour. Flavour of a
food is judged on the basis of the sensory message resulting from the combination of
taste and aroma. The temperature at which the food is served may have a very
important influence on the ability to detect taste and to evaluate flavour. The
extremes, whether very hot or cold, limit the ability of people to judge food
accurately. The best temperature range for flavour evaluation is 20-30°C. However,
some foods like ice creams should be evaluated at their serving temperature rather
than at the temperature range ideal for detecting taste and odour.
4) Texture
Texture indicates the characteristic of a food and would include descriptive
parameters like graininess, softness, chewiness, brittleness etc. The textural qualities
of a food have a relationship to the appearance of a product, as described previously
and to its evaluation in the mouth as well. Mouthfeel would include the textural
qualities of a food perceived in the mouth.
5) Consistency
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Both texture and consistency characterize the mouthfeel of the product. As the term
creamy indicates the consistency in an ice cream but is the textural attribute in the
fudge.
Sensory Evaluation of
Foods
With a brief review on the different attributes of foods, we will move on to describe
the various tests involved in sensory evaluation of food.
6.3
VARIOUS TESTS INVOLVED IN SENSORY
EVALUATION OF FOODS
Tests for sensory evaluation are of three types:
•
Difference testing - This is the sensory testing designed to determine whether
detectable differences exist between the products.
•
Preference testing - It is the sensory testing to determine the acceptability or
preference between products.
•
Descriptive testing - It is the testing which provides information on selected
characteristics of food samples.
Look up Unit 14, sub-section 14.4.1 in Course MFN-008 to get more details about
these tests. We shall focus on techniques of sensory evaluation next.
6.4
TECHNIQUES OF SENSORY EVALUATION
The various techniques used in the above mentioned tests for evaluation of food
samples are given in Table 6.1.
Table 6.1: Techniques of sensory evaluation
Techniques
Test characteristic
Single sample
This type of test is used to test acceptability and to aid in the decision on
future development of the product.
Paired
comparison
It is the difference test in which a specific characteristic is to be evaluated
in two samples, and the sample with the greater level of that
characteristic is to be identified.
Duo-trio test
Difference test in which two samples are judged against a control to
determine which of the two samples is different from the control.
Triangle test
Difference test in which three samples (of which two are same), and the
odd sample is to be identified.
Rank order
Preference or difference test in which all samples are ranked in order of
intensity of a specific characteristic.
Descriptive test
Use of key or descriptive words in sensory evaluation to characterize
food samples.
Profiling
It is a very detailed word description like texture profiling or flavour
profiling or characteristics such as chewiness, adhesiveness, hardness.
Descriptive scale
It uses array of words describing a range of intensity of a single
characteristic such as surface colour of a cake can be described as pale,
slightly brown, pleasing golden brown, dark brown, burned etc.
The scales can be designed with an odd number of points usually 5 or 9
point scales.
The above example is that of a 5- point rating scale.
Hedonic scale
Hedonic rating range from unacceptable to very acceptable is relatively
easy to construct and is effective when the desirable and undesirable
characteristics of a few samples are taken into account. The 9 point
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hedonic scale can be described as:
1= like extremely, 2= like very much, 3= like moderately, 4= like
slightly, 5= neither like or dislike, 6= dislike slightly, 7= dislike
moderately, 8= dislike very much, 9= dislike extremely
Smiley scale
This is a sequential series of very happy and continuing through to very
unhappy faces used in evaluating food products when respondents are
unable to use the language easily.
The evaluation of food requires a careful analysis of the ways of assessing food, the
properties of food, and the techniques for measuring these characteristics.
Sensory evaluation gives guidelines for the preparation and serving of samples under
controlled conditions so that the biasing factors are minimized.
We will learn about the requirements for the evaluation process next.
6.5
REQUIREMENTS FOR THE EVALUATION
PROCESS
Some of the requirements to be kept in mind for the evaluation of the products are
listed herewith:
•
People in a sensory test are often placed in individual test booths so that the
judgments they give are their own and do not reflect the opinions of those around
them.
•
Samples are labeled with random numbers so that the people they do not form
judgments based on the labels but rather on their sensory experiences.
•
Products may be given in different orders to each participant to help measure and
counterbalance for the sequential effects of seeing one product after another.
•
Standard procedures may be established for sample temperature, volume and
spacing in time, as needed to control unwanted variation and improve test
precision.
•
Clear instructions should be provided to the panelists before the evaluation
process as enumerated in Table 6.2. These instructions should be pretested by
having someone unfamiliar with sensory testing. Instructions regarding the filling
of the evaluation sheet should also be provided to the panelists.
Table 6.2 : Instructions to the panelists
S.No.
Instructions
1.
Please rinse your mouth with water before starting.
2.
Different codes have been provided for sensory evaluation.
3.
Taste each of the coded sample in the sequence presented.
4.
Rinse your mouth with water and proceed to the next code.
5.
You have to fill the evaluation performa code wise.
In any evaluation process, the individual sensitivity to different taste sensations
varies. Let us study more about this in our next section.
6.6
TASTE SENSITIVITY
The concentration of a substance (in saliva) required to trigger the sensation of taste
is much higher than the concentration of a substance (in air) required to provoke the
sensation of odour.
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The four primary tastes are not sensed equally. They are affected by time and
concentration. For example, salt on the tongue is sensed in a fraction of a second,
while bitter substance require a full second after it comes in contact with the tongue,
however, these bitter sensations tend to linger for a longer duration than any other
sensation.
Sensory Evaluation of
Foods
The concentration needed to bring about a sensation varies from one individual to
another.
The concentration required for identification is known as “threshold”. Individuals
differ in their sensitivity to the four sensations, and the threshold for each of the four
primary tastes is usually not at the same level in any of the individual.
In the following activities we will see how the individual threshold for different
sensations is varying.
6.7
DESCRIPTIVE ANALYSIS
Sensory methods may be used to quantify the perceived intensities of the sensory
attributes of a product. The quantification can be in terms of scaling of a product for
different perceived sensations. This procedure of quantification is known as
descriptive analysis.
Descriptive analysis is generally used in situations where a detailed specification of
the sensory attribute of a single product is required. These are frequently used in
product development to measure how close a new variation is to the desired product.
However, such testing requires trained panelist so that the results are consistent and
reproducible.
As descriptive analysis is very helpful in defining the quality attributes of a product
and is required in the evaluation of variations during product development, thus, for
your understanding we will conduct one activity to assess the sensory attribute of a
product.
Before we go into the details of product evaluation through descriptive analysis, we
must be familiar with various descriptors or selecting terms used to describe the
sensory attributes of the products. Let us get to know them.
6.8
PRODUCT DESCRIPTORS
Descriptors are selected terms used to describe the sensory attributes of products and
vary from one product to the other. The chosen descriptors should be non redundant
with other terms and should have no overlap with other terms used. Descriptors
should have certain desirable characteristics of being discriminating, representative
of the product quality, precise and reliable, unambiguous and should easily relate to
consumer acceptance or rejection.
Descriptive analysis technique involves judging a product on the basis of its
appearance, texture, taste, flavour and mouthfeel. It is a very helpful technique as the
key words used are made to describe the product for a producible and consistent
analysis.
Although this technique involves both quantitative and qualitative analysis of food by
using various methods as flavour profile technique/method, texture profile technique
and so on. However, these type of descriptive analysis would require trained panelists
for the purpose of evaluation. Thus, for our learning we would conduct a qualitative
descriptive analysis of a product. For example, a slice of white bread in our activity 2
to understand the concept of food analysis.
Before we start with the activity, let us list down various descriptors we would be
using for a slice of white bread.
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Example: A Slice of White Bread
A slice of white bread should be evaluated on the basis of its appearance, taste,
flavour, texture and mouthfeel. Let us take these attributes one by one to describe the
product characteristics.
•
Appearance
As studied earlier in section 6.2 of this practical, the appearance of a product would
involve colour (colour at the center and the colour of the crust), smoothness of the
surface, and uniformity of pores, glossiness or shine.
A slice of bread can be having white/creamy white colour at the center and the brown
colour on the crust. The intensity of the colour can vary both in the center and the
crust. A very light brown colour of the crust indicates inappropriate baking and a
darker shade of brown will indicate over baking of the product.
Smoothness/glossiness is the property of reflection of light from the surface and the
scattering of light by the surface over different angles which indicates smoothness or
roughness. Uniformity of pores indicate the moulding and fermentation of the bread
dough. The smooth surface of the slice can also be related to uniformity of the
surface. More the uniformity in the surface, more smooth it will appear and would
reflect more light. The surface may seem quite shiny but would not have the mirrorlike reflection.
•
Taste
Senses for taste stimulation have a strong influence on the acceptability of food
quality. The four primary tastes (sweet, salt, sour and bitter) are not sensed equally.
They are affected by time and concentration. The concentration needed to bring about
a sensation varies from one individual to another. Thus, the perception of each taste
sensation varies from one individual to another. A product may be rated as sweet,
less sweet, very sweet, depending on the individual’s sensitivity to the sweet
sensation. However, it is very important to characterize a product on the basis of the
attributes it should have and then the product can be rated by various individuals. A
slice of bread should be having a pleasant sweet taste. A sourish taste would indicate
the over fermentation or spoilage of breads whereas, slightly bitter taste would
indicate over baking of the product. Thus, the slice of bread can be evaluated in terms
of intensity of sweetness, sourness and bitterness it is having.
•
Texture
Texture can be divided into oral texture which involves the mouthfeel characteristics,
phase changes in the oral cavity and the tactile texture perceived when manipulating
the object by hand. The overall texture of this slice of bread both by the sensation of
eyes and taste can be included in the texture profile analysis. Before we go into the
details of the texture profile, we must understand a few textural attributes and their
definitions as indicated in the Table 6.3.
Table 6.3 : Various texture attributes used in the process of evaluation
S.No.
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Texture Attribute
Definition
1.
Adhesiveness
Force required to separate individual pieces adhering to each
other.
2.
Wetness
Amount of moisture perceived on the surface of the product,
when in contact with the upper lip.
3.
Roughness
Degree of abrasiveness of the product’s surface as perceived
by the tongue.
4.
Springiness
Force with which sample returns to its original size and
shape, after partial compression.
5.
Cohesiveness
Amount of deformation undergone by the material before
rupture when biting completely through sample with molars.
6.
Denseness
Compactness of the cross section of the sample after biting
completely through with molars.
7.
Fracturability
Force with which the sample ruptures when placed between
molars and bitten completely down at a fast rate.
•
8.
Hardness
9.
Adhesiveness
teeth
Force required to bite completely through sample placed
between molars.
to
Sensory Evaluation of
Foods
Amount of product adhering on/in the teeth after mastication
of the product.
Flavour
Bread has its own characteristic baked flavour. This flavour diminishes with shelflife. A freshly baked bread would have intense baked flavour than the bread which is
even one day old. With age, the flavour of bread changes from the baked flavour to
sourish flavour, which is indicative of spoilage or ripening. Even a fresh slice of
bread with over fermentation can have ripened flavour. Thus, the flavour can be
assessed on the scale of pleasant baked aroma to sourish aroma.
A key descriptor sheet is provided for your reference in the activity 2 wherein you
would be conducting the sensory evaluation using this.
Now, as you are familiar with the concept of sensory evaluation, let us get started
with our first activity, which is determination of individual taste threshold.
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ACTIVITY
1
Date: ………….
DETERMINATION OF THE TASTE THRESHOLD FOR
THE DIFFERENT SENSATIONS – SWEET, SALTY, SOUR
Aim: To determine the taste threshold for the three different sensations – sweet, salty
and sour.
Objectives
After conducting the activity included in this practical, you will be able to:
• perceive the individual differences existing for taste stimulation, and
• identify your own threshold and identification level for different taste
stimulations.
Principle
Sensitivity threshold test: Sensitivity tests are used to assess the ability of an
individual to detect the different tastes, odour and feel the presence of specific factors
e.g. astringency tests are used to select and train panel members for evaluating the
quality of products containing spices, salt, acid and sugar. For this purpose, threshold
tests for the recognition of basic tastes or odours are employed for selecting the panel
members. The threshold value is expressed numerically as:
Intensity score key
0
Name or taste of pure water
1
Different from material but quality not identifiable
2
Threshold very weak (taste identification)
3
Weak taste
4
Medium
5
Strong
6
Very strong
7
Extremely strong
These are two different taste thresholds. These include:
1) Stimulation threshold: In this state, the panel member recognizes the taste to be
different from pure water but is unable to identify the taste due to dilution.
2) Identifiable threshold: Here the panel member is able to identify the taste quality
as the taste is pronounced. The panel members are supplied with a series of
beakers containing the increasing concentration of substances with 1 of 4 primary
tastes. The member will start with beaker no. 1 and continue to taste the solution
in other beakers in the increasing numerical order.
Materials Required
Salt solution (%) -0.5, 0.8, 1.0, 1.2, 1.5
Sugar solution (%) - 0.05, 0.5, 0.7, 1.0, 1.2.
Citric acid (%) - 0.02, 0.04, 0.1, 0.5, 1.0
Spoons
Bowls
Beakers
Plain distilled water
Take a group of at least 10 subjects to carry out the process of sensory evaluation.
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Sensory Evaluation of
Foods
Procedure
Now carry out the activity step-by-step as enumerated herewith:
1) Prepare different concentration of sugar (sweet), salt (salty) and citric acid (sour)
as mentioned in the materials required.
2) The beakers should be placed in the increasing order of concentration.
3) The individual members tasting different concentrations should be having plain
distilled water after each tasting.
4) The individual should mark their stimulation threshold and identifiable threshold
in the observation table.
Results and Observations
Now note down your readings in the format given herewith. Under stimulation and
identifiable threshold column in the heading, indicate the total subject participating in
the exercise. Under different concertrations of stimulants, indicate the number of
subjects (out of the total) able to recognize each of the solution concentration:
S. No.
1.
Concentration (%)
Salt
0.8
3.
1.0
4.
1.2
5.
1.5
Sugar
Identifiable
threshold (by ------number of
subjects)
Your Intensity
score*
0.5
2.
6.
Stimulation
threshold (by ------number of
subjects)
0.05
7.
0.5
8.
0.7
9.
1.0
10.
1.2
11.
Citric acid 0.02
12.
0.04
13.
0.1
14.
0.5
15.
1.0
* Intensity score should be based on the 7-point scale given above under the
principle.
Inference
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……….. number of people were able to recognize the sweet taste at ……………%
sugar solution.
…………… number of people were able to recognize the salty taste at ……………%
salt solution.
…………… number of people were able to recognize the sour taste at ……………%
citric acid solution.
Conclusion
(Comment regarding your threshold and identification level)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
………………………………
Counsellor Signature
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ACTIV
2
CONDUCT A DESCRIPTIVE ANALYSIS OF A GIVEN
SAMPLE OF WHITE BREAD ON THE BASIS OF ITS
SENSORY ATTRIBUTES
Aim: To sensory evaluate the slice of white bread on the basis of appearance, taste,
texture and flavour.
Sensory Evaluation of
Foods
Date: ………….
Objectives
After conducting this activity, you will be able to:
• judge the product quality through sensory evaluation, and
• get familiarized with the use of various descriptors used in the evaluation
process.
Principle
Refer section 6.7 and explain what do you understand by descriptive analysis in the
space provided herewith.
Refer to section 6.8 and describe what are descriptors in the space provided herewith:
Materials
Two different samples of white bread slices – coded 001 and 002
Sheet for analysis
Any instructions
Glass of water
Napkins
Sample disposal arrangements
Procedure
Carry out the activity according to the steps enumerated herewith:
1) Read out the instructions carefully (provided in Table 6.2 given earlier in section
6.5).
2) Write the name and code of the sample provided at the top.
3) Fill in the descriptive evaluation proforma for each code separately.
4) Carry out your own individual sensory analysis for the given sample.
5) Take precautions while filling in the proforma for unbiased results.
6) Analyze the data for the product characteristics and report.
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Observation
Descriptive evaluation Proforma
Sample identified as : ………………………………..
Code of the sample provided : ………………………………..
Sample size : ………………………………..
Serving temperature : ………………………………..
Tick mark the most closely describing anchor word for the listed attributes of the
given sample:
Evaluation criteria
Appearance
Attributes
Anchor words
Colour of the center of the slice white- creamy white
Colour of the crust
light brown-golden browndark brown
Uniformity of pores
uniform- non uniform
Surface area
smooth-rough
Glossiness
shiny-dull
Feel
hard-soft-sticky
Taste
Taste during chewing
After taste
sweet-bland-sour
sour-bitter-sweet-none
Texture
Tissue adhesiveness
Brittleness
Chewiness
Elasticity/springiness
Hardness
sticky-tacky-gooey
crumbly- crunchy- brittle
tender- chewy- tough
spongy- elastic
soft- firm- hard (dry)
Flavour
Flavour before and after biting pleasant baked flavour-sour
-ripened flavour
As you have conducted descriptive evaluation of code 001, next carry out the
descriptive analysis for the code 002.
Sample identified as : ………………………………..
Code of the sample provided : ………………………………..
Sample size : ………………………………..
Serving temperature : ………………………………..
Tick mark the most closely describing anchor word for the listed attributes of the
given sample:
Evaluation criteria
112
Attributes
Anchor words
Appearance
Colour of the center of the slice white- creamy white
Colour of the crust
light brown-golden browndark brown
Uniformity of pores
uniform- non uniform
Surface area
smooth-rough
Glossiness
shiny-dull
Feel
hard-soft-sticky
Taste
Taste during chewing
After taste
sweet-bland-sour
sour-bitter-sweet-none
Texture
Tissue adhesiveness
Brittleness
Chewiness
Elasticity/springiness
Hardness
sticky-tacky-gooey
crumbly- crunchy- brittle
tender- chewy- tough
spongy- elastic
soft- firm- hard (dry)
Flavour
Flavour before and after biting pleasant baked flavour-sour
-ripened flavour
Now, when you have carried out the descriptive analysis for both the samples, study
their product characteristics in detail. Report your findings in the table given below.
S.No.
1.
Attributes
Evaluation
criteria
Appearance
Code 001
Sensory Evaluation of
Foods
Code 002
Colour of the center of the
slice
Colour of the crust
Uniformity of pores
Surface area
Glossiness
Feel
2.
Taste
Taste during chewing
After taste
3.
Texture
Tissue adhesiveness
Brittleness
Chewiness
Elasticity/springiness
Hardness
4.
Flavour
Flavour before and after biting
Interpretation:
Code 001
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Code 002
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Conclusion
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
……………………………..
Counsellor Signature
113
PRACTICAL 7 CHEMISTRY OF COLLOIDAL
PARTICLES
Structure
7.1 Introduction
7.2 Colloidal Systems in Foods
7.3 Gels
7.4 Foams
7.5 Emulsions
Activity 1: Study the Effect of Various Additives on the Stability of Egg White
Foam
Activity 2: Demonstration of the Effect of Foaming in Preparation of Cold and Hot
Soufflé
Activity 3: Determination of the Best Method of Preparing a Stable Emulsion
7.1
INTRODUCTION
Unit 7 in the theory course presented a detailed review on the colloidal system – their
nature and properties. The focus was on foams, gel, sols and emulsions. Here in this
practical, we will get hands down experience of preparing these colloidal systems and
analyzing their properties and factors which influence them. There are three activities
in this practical.
Objectives
After studying this practical and undertaking the activities given herewith, you will
be able to:
• define and identify different colloidal systems (gels, foams, emulsions etc.)
• recognize the different stages of foam formation and explain the factors
influencing foam formation,
• apply the concept of foam development in preparation of various foods,
• prepare hot and cold soufflés and learn about factors affecting formation of
soufflés, and
• prepare stable emulsions and recognize the factors affecting the formation of a
stable emulsion.
7.2
COLLOIDAL SYSTEMS IN FOODS
A colloidal system is a heterogeneous system. The material that forms the base of the
system is called the dispersion medium or the continuous phase. The material that
exists in the colloidal condition is called the dispersed medium or the discontinuous
phase.
Of the three states of matter (solid, liquid and gas), eight classes of colloidal systems
can be formed. Solid in a solid, a solid in a liquid, a solid in a gas, a liquid in a gas, a
liquid in a liquid, a liquid in a solid, a gas in a solid and a gas in a liquid. Look up
sub-section 7.2.1 in the Unit 7 in the theory course (MFN-008) which presents this
classification.
Colloidal particles, we also learnt, are in motion and are electrically charged.
Colloidal systems may be lyophilic or lyophobic. These properties affect viscosity, as
even changing the concentration of solutes like sugars and salt and the addition of
electrolytes may cause precipitation.
114
The colloidal property of adsorption makes it useful in cookery, giving protection
against precipitation and agglomeration. Another property of imbibition, is the ability
to pick up water and swell. Components such as starch, proteins and fat when
dispersed in water forms colloids.
Examples of such dispersion in our food system are the formation of gels, foams and
emulsions. Some of the colloidal systems in foods are listed in the Table 7.1.
Chemistry of Colloidal
Particles
Table 7.1: Colloidal Systems in Food
S. No.
Name of the
colloidal system
Dispersed
phase
Continuous
phase
Example in food
1.
Emulsion
Liquid
Liquid
Salad dressing
2.
Sol
Solid
Liquid
Gravy
3.
Gel
Liquid
Solid
Baked custard
4.
Foam
Gas
Liquid
Egg white foam
5.
Suspensoid
Gas
Solid
Whipped gelatin
In this practical, we will be highlighting the properties of gels, foams and emulsions
with various factors affecting their formation. We begin with the properties of gels.
7.3
GELS
Gels may be formed by the proteins of egg or flour in products like soufflés,
puddings, custards, batters and doughs. When the protein particles are dispersed in
water, the solution like mixture results in the formation of a sol. When a sol assumes
a rigid form, it is referred to as a gel.
The change of sol to gel form may be brought about by a change of concentration of
the dispersed phase, a change in temperature, or a change in the hydrogen-ion
concentration or electrolyte content.
Gel formation takes place when the dispersed phase develops into a network structure
that holds the liquid phase in its meshes. In some gels, the framework can be broken
by agitation or heat. When this happens, the gel structure reverts back to the sol form.
However gels formed as in case of baked custards are of non-reversible types.
When only a part of sol changes to the gel form, the process is known as flocculation.
An example of this process can be seen in heated milk when a precipitate coats the
bottom of the pan.
Syneresis is the process when the gel on shrinkage results in the loss of liquid. This
process was first observed in 1861 by T. Graham, who described the process as an
exudation of small amounts of liquid on standing because of a slight contraction of
the gel. Although no net volume change occurs in the gel, syneresis cannot be
described as a reversible process.
7.4
FOAMS
Foods like meringue, ice cream and beer contain foams. A number of foods possess
good foaming properties on account of the proteins they contain that can provide the
stability to products and impart characteristic qualities to foods.
Surface proteins are stretchy and flexible almost like a loose rubber sheet, which
provide resistance to disruptive shear forces and compression/dilatation forces. This
is obtained by denaturation/unfolding of polypeptide chains and exposing substantial
regions of hydrophobic residues into air or lipid phases where they are stable. The
ability of the protein films to resist shearing and high level stretching capability
contributes to good foaming and emulsifying properties. These properties are
provided from extensive interactions between protein molecules and reach a
maximum at the isoelectric point of the protein where electrostatic repulsion is at a
minimum.
Foaming is characterized by a foam expansion index (FEI) which indicates the foam
formation property of any product and a foam liquid stability (FLS) which is the
indicator of the strength of foam. The foam expansion index and the foam liquid
stability of proteins is given in Table 7.2.
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The foam expansion ratio is the ratio of the weight of a given volume of expanded
foam to the weight of that same volume of unexpanded foam solution.
Table 7.2: The foam expansion index and the foam liquid stability of proteins
Protein
FEI %
FLS %
Whey protein
600
21
Egg albumin
240
24
Casein
460
14
Soya (hydrolyzed)
500
10
Gelatin
760
55
0
0
Lysozyme
From Table 7.2 it can be observed that casein forms good foam which is not stable.
Egg forms a stable foam. Whereas gelatin provides good amount of foam that is also
stable. Thus, we can say that not all proteins foam equally well and not all of the
foams are particularly stable.
Foam is caused by the protein film lowering surface tension i.e. cohesive force of
water molecules that tend to collapse a bubble, and give resistance to shearing/tearing
with high level of stretching capacity. So when protein solution is whipped or stirred
vigorously, air is pulled down into solution and when it tries to escape up, flexible
protein surface forms a bubble.
Next, let us review the properties of different food foams such as milk foam, cream
foam and egg white foam.
A) Milk Foams
The proteins and water in milk are extended into thin films by agitation. These thin
films enclose small air bubbles to make foam in which the protein and water provide
the continuous network of the colloidal dispersion, and the air is the discontinuous or
dispersed phase. This arrangement is possible because the native proteins in milk
have a low surface tension and low vapour pressure. The low surface tension makes it
possible to spread the liquid proteins into thin films, and the low vapour pressure
reduces the likelihood that evaporation will occur.
In fluid milks, the concentration of protein is too low to permit the production of
foam with any stability. However, evaporated milk can be whipped into foam with a
very large volume. The increased protein and fat concentrations of undiluted
evaporated milk make it possible for the foam to form, and the foam will even have
some limited stability. Foam formation and stability are enhanced if the undiluted
evaporated milk is chilled until ice crystals start to form in it. This condition causes
the fat to be rather firm, which concentrates the protein in the remaining unfrozen
water and also helps to give some rigidity to the cell walls in the foam.
Stability can be achieved by adding lemon juice because the acid promotes
precipitation of the milk proteins to give more strength to the cell walls.
B) Cream Foams
Cream, with a fat content of at least 30 per cent, can be beaten to form foam.
However, it is observed that a cream with 36 per cent fat can be beaten quickly to
more stable foam.
The fat contributes considerable rigidity to the cell walls in whipped cream foam that
is kept chilled. Over beating whipped cream causes reversal to water-in-oil emulsion.
Butter results.
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As fat is the principal component contributing to the strength of the cell walls, it is
essential that whipped cream be stored under refrigeration until the time it is served.
If cream is allowed to begin to warm to room temperature, the fat will start to soften,
and the rigid cell walls containing the warming fat will weaken. If warm enough, the
whipped cream foam may melt into a liquid system.
C) Egg White Foams
Egg white foams when whipped or beaten, the air gets entrapped in the liquid
present, and an interfacial tension is established between the air-liquid interface. The
three proteins which are responsible for foam formation in eggs are globulin,
ovalbumin and ovomucin. On beating, ovomucin gets sheared to form hollow tubes
about 300-400µ in length. The foam is further helped by some protein coagulation at
the air-water interface. With agitation, the egg albumin can be spread over a large
surface area, and air can be incorporated into bubbles created by beating the proteins.
Some of the proteins are denatured by beating action and then aggregate to enhance
stability of the developing foam. Figure 7.1 illustrates the egg white foam.
Chemistry of Colloidal
Particles
Figure 7.1: Egg white foam
Foams need to be stable if they are to have a role in food preparation. Stability is
enhanced if the surface tension is low, if vapour pressure is low, and if a substance
solidifies on the surface of the bubbles. Egg white meets all of these requirements,
making it a particularly useful food when foam is desired.
Egg foams at different stages of formation, as illustrated in Figure 7.2, have many
applications in food preparation and processing such as:
1) Soft peak stage, as shown in Figure 7.2(a), is used in the preparation of baked
products like cakes, meringues, soufflés.
2) The stiff peak stage of foam, as shown in Figure 7.2(b), is needed for hard
meringues and chiffon cakes, as well as sponges and soufflés.
3) The initial peak stage can be used for clarifying soups and consomme.
4) Products like french toasts, fluffy omelets, angel cakes require egg foams.
Figure 7.2: Foam formation in egg white
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Having looked at the properties and applications of egg white foams, we move on to
the stability of egg foams.
Egg foam stability
The two factors of utmost importance in egg white foams are stability and volume.
Several factors influence one or both of these characteristics and are of significance
regardless of the product into which the foam is ultimately incorporated.
The extent of beating is an important factor in stability of egg white foam. As beating
progresses, the foam becomes increasingly stable up to a critical point, after which
continued beating decreases stability. Maximum stability is reached when the whites
just bend over, but before maximum volume has been reached. If beating continues
beyond the point of maximum stability, the surface begins to look slightly dry, and
the foam exhibits some brittleness. Foam formation is delayed when the whites are
well below room temperature.
You would realize that there are various ingredients which influence the stability of
egg white foams. We shall review these ingredients, next.
Effect of addition of ingredients on egg white foam stability
The addition of other ingredients also influences stability. Sometimes salt is added to
an egg white foam for flavour, but this addition reduces stability slightly.
Occasionally recipes include some added liquid in making egg white foam. This
dilutes the proteins in the foam and decreases stability. If yolk happens to
contaminate the white at all, as can happen during the separation of yolks and whites,
stability of the foam formed from the whites is reduced.
Not all ingredients reduce stability. In fact, the addition of sugar has a very laudatory
effect on foam stability. A possible explanation is that the addition of sugar delays
foam formation significantly, which means that considerably more beating is
necessary to reach the proper stage of foam development. This increased beating
results in foam with a finer texture and more surface area. This foam is stabilized
with protein that has been partially denatured by beating.
Acidic ingredients, commonly either cream of tartar or lemon juice, are useful
stabilizing agents when making egg white foams, particularly when added early in
the formation of the foam. Although stability is promoted by reducing the pH of the
egg white foam, formation of the foam is delayed by this addition. Again, the delay
in reaching the desired end point in whipping the foam results in increased total
agitation and a finer, more stable foam. Cream of tartar is particularly effective as the
acid ingredient when the pH of the white foam approaches pH 6.0, whereas, citric
acid and cream of tartar are about comparable in their effect at pH 8.0.
With this, we come to an end of our discussion on foams, next let us look at the
emulsions.
7.5
EMULSIONS
Emulsions, as you may already know by now, are colloidal dispersions of a liquid in
another liquid with which it is immiscible. Emulsions can be formed by shaking the
two liquids together until they appear to be well mixed. Shaking provides the energy
needed to enable the liquid with the higher surface tension to form many small
droplets or spheres which then are surrounded by the other liquid. Formation of these
numerous small spheres creates a far larger surface area for the dispersed liquid that
was the case when two liquids were in contact as two layers.
The droplets of the dispersed phase tend to coalesce when they bump into each other
as they move through the emulsion because the one large droplet represents a lower
energy state than two. Because one large droplet has less surface area than two small
droplets, thus the droplets in an emulsion continue to coalesce into larger droplets
until the emulsion breaks or separates into two distinct phases.
118
Emulsions, as you may recall studying in Unit 7 in the theory course (MFN-008), are
classified on the basis of the type of liquid constituting each of the phases. Let us
quickly review the classification and types of emulsions once again.
Chemistry of Colloidal
Particles
Classification of Emulsions
Emulsions are classified as:
•
Oil-in-water emulsion: This is a colloidal dispersion in which droplets of oil are
dispersed in water. Example is mayonnaise. Look at Figure 7.3 which illustrates
the oil-in-water emulsion.
Figure 7.3: Oil-in-water emulsion
•
Water-in-oil emulsion: This is a colloidal dispersion in which droplets of water
are dispersed in oil as illustrated in Figure 7.4. Example of water-in-oil emulsion
is butter.
Figure 7.4: Water-in-oil emulsion
What are the types of emulsions?
Emulsions can be of three types:
1) Temporary emulsion: These require vigorous shaking just before they are used,
as they separate out easily on storage, as used in French dressing and Italian
dressings. Such emulsions exhibit a low viscosity.
2) Semi permanent emulsion: Such emulsions have viscosity of thick cream and
thus are more stable than the temporary emulsion. Examples of such emulsions
are salad dressings containing syrups, honey and condensed soups.
3) Permanent emulsions: These are characterized by a very high viscosity and
therefore are very stable. They contain emulsifiers and stabilizers which aids to
their stability. Example of this category is mayonnaise.
With a basic understanding about the types of emulsions, let us also review the uses
of emulsions in food preparation.
Uses of Emulsions
Emulsions provide many useful functions in food preparation and processing. They:
1) act as vehicles for flavour to foods,
2) dilute ingredients,
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3) hide objectionable odours or tastes,
4) provide variety in food preparation,
5) control agglomeration of fat globules in food products,
6) modify the rheological properties of doughs, by reacting with gluten proteins,
7) improve wettability and dispensability of dehydrated products,
8) modify crystals in candies, and
9) dissolve flavours and essential oils in micelles of aqueous systems.
Having looked at the uses of emulsions next, let us learn about the stability of
emulsions.
Emulsion stability
The stability of an emulsion is determined by the viscosity of the continuous phase,
presence of an emulsifier, the concentration of the emulsifier, size of the droplets and
the ratio of the dispersed phase to the continuous phase. Interfaces in emulsions and
foams can be stabilized by:
•
•
•
small molecule surfactants,
adsorbed macromolecules – often proteins, and
fat globule networks.
We have studied above that the stability of an emulsion is influenced by emulsifiers.
What are emulsifiers? Let’s get to know them.
What is an Emulsifier?
An emulsifier is a compound that contains both polar and nonpolar groups and thus
is drawn to the interface between the two phases of an emulsion to coat the surface of
the droplets. The nature of the emulsifier influences the type of emulsion that is
formed. If it is attracted more strongly to water than to oil, the surface tension of
water is reduced more than that of oil. The result is the formation of an oil-in-water
emulsion. What is the role of the emulsifier in food systems? Let us find out next.
The major functions of emulsifiers in food systems are as follows. The emulsifier:
•
•
•
•
•
•
•
•
modifies the intermolecular forces which stabilize or destabilize the structure of
food colloids and gels,
lowers the interfacial tension between two liquid phases or liquid-air phases,
reduces the pressure gradients required to disrupt the droplets when forming a
dispersion,
reduces the tendency of droplets once created to coalesce,
alters the flow properties,
modifies the crystallization of fats/oils,
improves whipping quality of foam, and
interacts with starch and protein components in foods, which modify texture and
rheological properties.
So we have seen that emulsifiers have an important role to play in food systems.
There are different types of emulsifiers, which can be used. Let us look at these
different classes of emulsifiers next.
Classification of emulsifiers
Emulsifiers can be classified under two categories. These are:
•
120
Natural: These are naturally present in foods. Some examples are phospholipids
and lecithin in egg yolk, which are responsible for the natural stability of
mayonnaise and other products.
•
Synthetic: These are chemicals prepared in the laboratories, which are used to
stabilize food products. These are further classified as emulsifiers affirmed as
GRAS (Generally Regarded As Safe) and emulsifiers as direct food additives
Chemistry of Colloidal
Particles
Table 7.3 gives the list of these commonly used food emulsifiers.
Table 7.3: Common food emulsifiers
S.No.
Emulsifier
Typical Applications
Emulsifier affirmed as GRAS
1.
Lecithin
Margarines, chocolate products
2.
Monoglycerides
Margarines, whipped cream, ice-cream
3.
Diacetyl tartaric acid
Baked goods, confectionary, dairy products
4.
Monosodium salt of phosphated
monoglycerides
Dairy products, soft candy
Emulsifiers
additives
as
direct
food
1.
Lactylated monoglycerides
Baked goods, whipped toppings
2.
Acetylated monoglycerides
Pizza
3.
Succinylated monoglycerides
Shortenings, bread
4.
Ethoxylated
monoglycerides/
esters (TWEENs)
Cakes, whipped toppings, frozen desserts
5.
Sorbitan
(SPANs)
Confectionary coatings, yeast cakes, icings
6.
Polyglycerol esters
Icings, salad oils, peanut butter, fillings
7.
Sucrose esters of fatty acids
Baked foods, fruit coatings, confectionary
8.
Polysorbates
Salad dressings, coffee whiteners, ice creams
9.
Propylene glycol esters
Cake mixes, whipped toppings
monostearate/esters
GRAS: Generally Regarded As Safe
With this basic knowledge, let us now carry out the activities given in this practical.
There are three activities included in this practical. So get started.
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ACTIVITY
1
Date: ………….
STUDY THE EFFECT OF VARIOUS ADDITIVES ON THE
STABILITY OF EGG WHITE FOAM
Aim: To study the effect of various additives on the stability of egg white foam.
Objectives
After undertaking this activity, you will be able to:
•
recognize the different stages in the foam formation,
•
explain the effect of various factors in foam formation, and
•
apply the concept of foam development in preparation of various food.
Principle
The two factors of utmost importance in egg white foams are stability and volume.
Several factors influence one or both of these characteristics
The extent of beating is an important factor in stability of egg white foam. As beating
progresses, the foam becomes increasingly stable up to a critical point, after which
continued beating decreases stability.
Maximum stability is reached when the whites just bend over, but before maximum
volume has been reached. If beating continues beyond the point of maximum
stability, the surface begins to look slightly dry, and the foam exhibits some
brittleness. Foam formation is delayed when the whites are well below room
temperature.
Addition of ingredients
The addition of other ingredients also influences stability. Comment on the stability
of foams as influenced by the addition of the following ingredients in the space
provided herewith. We have already discussed about these effects earlier in section
7.4 under the heading egg foam stability:
Addition of Salt
Addition of Egg Yolk
Addition of Sugar
Acidic Ingredients
122
Equipments
Measuring cylinder, funnel, stopwatch, filter paper, beater (rotatory, whisk beater).
Chemistry of Colloidal
Particles
Materials
Eggs, salt, castor sugar, cream of tartar, fat, distilled water.
Procedure
Now carry out the experiment step-by-step as enumerated herewith:
A) Preparation of white egg foam.
i)
Separate the white from the yolk egg.
ii) Beat egg white to stiff peak using a rotary beater or a whisk and note the time
taken for foam formation.
iii) Transfer the prepared foam to a funnel lined with filter paper and placed over
a measuring cylinder. Keep aside for 45 minutes and record the volume of
the liquid drained.
Use one egg white for each of the variations given below and carry out the variations
B to I repeating the procedure of preparation of egg white foam as given above in A
(i-iii).
B)
Add 1/8th teaspoon salt to egg white for preparing the foam.
C)
Add 1/8th cream of tartar and then beat.
D)
Add 1/4th of egg yolk and then beat to attain the foam
E)
Add 10 ml of water and then beat
F)
Add 2 teaspoon of castor sugar and prepare the foam
G)
Add 10 ml distilled water and proceed
H)
Add 10ml oil and beat
I)
Use a different type of beater
After keeping the foams for 45 minutes, compare the results of the samples A to I
(total of 9 samples) with respect to time taken for foam formation, colour of the foam
formed, stiffness, dullness or shiny texture and other sensory attributes to determine
the most stable foam. Record your observations in the format given on page 124
under results and observation section.
Precautions
1) Egg white should be separated carefully from the yolk so as not to mix even at
trace of the yolk.
2) Beating should be done till the stiff peak stage only.
3) Added substances should be measured accurately.
4) Time should be noted when the stiff peak is reached.
5) All samples should be neatly labeled on completion and drained for exactly 45
minutes before observations are recorded.
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Results and Observations
Principles of Food
Science
Record the observations made as indicated in the format given herewith. Record the
effect of added substances on foam formation:
Variation
Time
(min)
Colour
Foam
Liq.
Texture
Foam
Liq.
Gloss (shiny
or dull)
Stability
(Yes/no)
Drained
Liquid (ml)
Applications
Egg white
A.
B.
C.
D.
E.
F.
G.
H.
I.
From the above observations, inferences may be drawn regarding the stability and
suitability of various foams for food preparation and processing.
Inference
Egg white foam when treated with acid results in……………………
Egg white foam when treated with salt results in……………………
Egg white foam when treated with sugar results in……………………
Egg white foam when treated with oil results in……………………
Egg white foam when diluted with water results in……………………
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Conclusion
(Comment regarding the stability and suitability of various foams for food
preparation and processing)
Chemistry of Colloidal
Particles
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
Submit the activity for evaluation.
……………………………..
Counsellor Signature
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ACTIVITY
DEMONSTRATION OF THE EFFECT OF FOAMING IN
2
PREPARATION OF COLD AND HOT SOUFFLÉS
Date: ………….
Aim: To demonstrate the effect of foaming in preparation of cold and hot soufflés.
Objectives
After undertaking this activity, you will be able to:
• learn how to prepare hot and cold soufflé, and
• explain about the various factors affecting formation of hot and cold soufflés.
Principle
Soufflés are egg white foams, which can be modified to prepare savory or sweet
dishes. These preparations usually involve beating of egg whites till they foam to
peak stage and then folding them into a flavoured base of other ingredients. If served
hot, they are usually baked just before service so as to prevent the foam from
collapsing on cooling. In such preparations the air entrapped in the mixture during
foaming expands on heating to give volumes, which may be 2- 2 ½ times greater on
cooking. This results in products having a light soft texture and mouthfeel. However,
on keeping the product, its volume decreases due to some of the entrapped air
bubbles escaping where the protein fibers are weak, having lost their elasticity. A
well-made product shows only slight variations in the volume because of denatured
surface proteins on foaming, provide enough elasticity to stabilize the product. When
served cold they are refrigerated immediately after the mixture is ready so that the
protein films formed around the air bubbles get set preventing their escape and
maintaining the volume of the desert.
Equipments
Baking dish, soufflé dish, frying pan, weighing scale, measuring cups, spoons,
spatula, beater refrigerator and oven.
Materials
Eggs, cream, lemon or orange, castor sugar, gelatin, water, essence, butter paper.
Procedure
Now carry out the activity step-by-step as enumerated herewith. Start with the
preparation of cold soufflé.
A)
Preparation of a cold soufflé
i)
ii)
126
Prepare a soufflé dish.
Wash and dry a small lemon. Grate the rind, extract the juice and keep
aside.
iii) Take one egg, separate the white from the yolk, putting the yolk in a bowl
along with ¾ of lemon extract and 30 g of sugar.
iv) Place the bowl containing the mixture in a double boiler in which the water
is simmering at 97ºC and beat or whisk until creamy.
v)
Remove the bowl from the boiler and continue beating till the mixture is
cool.
vi) Sprinkle 5 g gelatin in 30 ml water and keep aside for few minutes to swell.
Then stir to dissolve.
vii) Add the gelatin to the egg yolk mixture gradually and mix well. Place in
the refrigerator to set.
viii) Whip 80 g cream, and beat egg whites till peak stage.
ix) Fold in whipped cream and the stiff egg white into slightly set yolk
mixture.
x)
Pour the mixture into the prepared soufflé dish and leave in the refrigerator
till set. Gently remove the paper from the dish before serving.
Next, follow the steps given herewith and prepare the hot soufflé.
B) Preparation of hot soufflé
i)
Chemistry of Colloidal
Particles
Melt 12 g butter in a saucepan. Add 12 g flour and stir cook for 1-2 minutes.
ii) Gradually add ¼ cup of scalded milk stirring continuously till it comes to a
boil. Cook till the mixture coats the back of a spoon and remove from fire.
iii) Prepare orange rind and extract juice of ½ orange. Stir the juice and 10 g of
castor sugar into the sauce prepared in (ii).
iv) Allow the mixture to cool and beat in ½ egg yolks.
v) Whisk the egg whites to stiff peak stage and gently fold them into the
prepared yolk mixture.
vi) Spoon the mixture into a greased oven-proof dish and bake at 175ºC for 20
minutes.
vii) Serve hot decorated with orange rind.
C) Make variations in the soufflé recipes A and B with regard to:
i)
The kind of beater used – rotatory or electrical blender.
ii) Improper yolk – white separation i.e. partial mixing of egg yolk and white.
iii) Amount of added ingredients (vary the amounts of different ingredients
required for the preparation of soufflé like using more flour than required,
using less egg white also one can vary the process as egg white not beaten to
a stiff peak stage or in cold souffle addition of cream without whipping).
Subject the samples to sensory evaluation and carry out the percent sag as given
below.
Percentage sag
Percentage sag is used to determine the firmness of a product. To calculate the
percentage sag for cold souffle follow the steps given below:
1)
2)
3)
4)
Pierce a toothpick vertically in the centre of the set soufflé and pull it out.
Measure the moist level with the help of a scale.
Note down the reading (mm). This reading is R1.
Loosen the sides of the set gel with a moist knife and invert the gel on the centre
of a plate.
5) Again take the reading as in steps 1-3. This is R2.
6) Calculate the percentage sag using the formula:
R1 − R 2
R1 × 100
To calculate the Percentage Sag in Hot soufflé carry out the following process:
1) Pierce a toothpick vertically in the centre of the hot soufflé immediately after it is
taken out of oven and pull it out.
2) Measure the moist level with the help of a scale.
3) Note down the reading (mm). This reading is R1.
4) You will observe the centre sag of the product after some time, now pierce a
toothpick vertically in the centre of the hot soufflé which has sagged.
5) Again take the reading as in steps 1-3. This is R2.
6) Calculate the percentage sag using the formula:
R1 − R 2
R1 × 100
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Precautions
1) Use dishes with vertical sides for making soufflés.
2) To prevent sticking, coat the baking dish with butter and sugar. For cold soufflés
rinse out the dishes with water and do not wipe dry.
3) Bake or refrigerate immediately after the foam mixture is ready. Do not freeze.
4) Preheat oven and bake at 180ºC to obtain a dry and stable product.
5) Leave soufflés in the oven for 5-10 minutes after switching off.
6) To prevent their sudden collapse on serving, open the oven door slightly to
enable temperature to gradually come down and stabilize the product.
Results and Observations
Record the observations made through evaluation of i, ii and iii in point C above,
with respect to volume, % sag after 10 minutes at room temperature, texture, taste
and acceptability (sensory evaluation) in the format given herewith.
S. No.
1)
Variations
Variations in cold
soufflé
a)
b)
c)
d)
e)
f)
2)
a)
b)
c)
d)
e)
f)
128
Variations in hot
soufflé
Percent Sag
Sensory evaluation
Inference (with regard to)
i)
Quality of souffle with regards to the kind of beater used
Chemistry of Colloidal
Particles
ii) Quality of soufflé with regards to improper yolk – white separation
iii) Quality of soufflé with regards to amount of added ingredients
Conclusion
(Indicate the applications of the foams as used in food preparation).
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
Submit the activity for evaluation.
……………………………….
Counsellor Signature
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ACTIVITY
3
DETERMINATION OF THE BEST METHOD OF
PREPARING A STABLE EMULSION
Date: ………….
Aim: To determine the best method of preparing a stable emulsion like mayonnaise.
Objectives
After undertaking this activity, you will be able to:
•
learn the process of preparation of a stable emulsion, and
•
discuss the various factors affecting the formation of a stable emulsion.
Principle
Mayonnaise is an emulsified salad dressing, which requires ingredients in certain
proportions to be mixed together to form a stable oil-in-liquid emulsion. The egg
forming about 20% of the total weight provides the emulsifying agent lecithin,
present in the yolk. This helps in stabilizing the other ingredients in the mixture.
While whole egg may be used in the preparation of the product, it is the yolks, which
have better stabilizing ability as they hold moisture in dispersion. Therefore the ratio
of other ingredients such as salt, vinegar and spices should not exceed 65:10:5
percent of the weight of the egg contents, since the yolks have limited assimilating
power. Continuous beating breaks up the oil into fine globules, which get
simultaneously dispersed in liquid to convert it into a semisolid stable product.
Equipments
Rotary beater or whisk, blender, bowl, standard cups and spoons
Materials
Eggs, 1 cup refined oil, 1tablespoon vinegar, ½ teaspoon salt, ½ teaspoon sugar,
½ teaspoon mustard powder.
Procedure
The activity is divided into three sections A, B and C to study the effect of variations
on the end result and determine the most suitable method of preparing mayonnaise
for different applications. So carry out the activity following the steps indicated
herewith:
A)
B)
Method of preparing mayonnaise
i)
Separate yolks from the eggs and drop into small bowl.
ii)
Add all the ingredients except vinegar and oil to the yolks.
iii)
Beat with a whisk or beater till ingredients are well blended.
iv)
Add the oil drop by drop alternating it with the vinegar while
continuously beating the mixture. Continue beating till the mixture
begins to thicken.
v)
Continue the process, gradually increasing the quantity of oil added at
one time, till all the ingredients have been used up and the resultant
product is spoonable into a jar.
vi)
Observe samples for microscopic structure, colour, consistency, taste,
flavour and applicability.
Effect of varying the method of combining ingredients
i)
130
Add seasonings and vinegar to the yolks and then start the whisking. Add
oil as in ‘A’ (iv – v) and when ready, keep sample aside for assessment.
ii)
Beat the egg yolks first and then add the oil drop by drop till thickened,
followed by spices and vinegar. Set the sample aside.
iii)
Chemistry of Colloidal
Particles
To the yolk, add seasoning, 1/3 vinegar and then oil drop by drop
beating till thickened, followed by 1/3 vinegar again and then the rest
of the oil and the remaining 1/3 vinegar to complete the product. Keep
sample aside.
For quick and even continuous beating, an electrical blender may be used and the
ingredients continuously added without much pause following the method in A(i-vi).
With this method, the time can be monitored for equal number of revolutions when
variations are used.
C) Effect of substituting emulsifying agents
i)
Make A starch gel with ½ T (tablespoon) of cornstarch add ½ cup of water.
Cool the gel. Take 2 T of this gel and add it to the egg yolks with all the
other ingredients except oil, and mix together. Add oil as in A (iv) and follow
procedure till A (vi). Keep sample aside.
ii) Prepare a gel using 2T gelatin in ½ cup water and cool to room temperature.
Use 1T of gel to make the emulsion as in (i) above. Keep sample aside.
iii) Substitute egg white for yolk and proceed as in A (i-vi). Keep sample aside.
iv) Substitute whole egg for yolk and proceed as in A (i-vi). Keep sample aside.
D) Effect of temperature of ingredients on formation of emulsion
i)
Add vinegar and seasoning to egg yolk at room temperature, then mix and
refrigerate till cold. Keep the oil for some time in the fridge too. Remove
from fridge and note the temperature of the mixture and oil. Place bowl in ice
and add cold oil as in experiment A till ready. Keep aside.
ii) Heat oil and vinegar separately to 100ºC. Combine the ingredients as in ‘A’
till ready. Keep aside for assessment.
Note: Temperature plays an important role in the formation of an emulsion. As
temperature rises the surface tension of the continuous phase gets reduced, and the oil
too becomes more mobile and less viscous.
Precautions
1) The oil should be added drop wise initially and then gradually as the emulsion
forms.
2) Beating should be continuous while preparing the product.
3) Proportion of ingredients should be exactly controlled for all samples even when
substitutes are used.
4) Proportion of ingredients should be strictly controlled for all samples even when
substitutes are used.
5) Adding oil and vinegar alternately is essential for dispersion.
6) Temperature must be kept constant throughout the experiment.
Results and Observations
All the samples should be labeled correctly and assessed for appearance, consistency,
taste, mouthfeel and application in food preparation and service. Record the results in
the format given herewith.
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Sensory quality of mayonnaise for different variations.
Variation
Appearance
Stability
Taste
Mouth feel
Application
A
B (i)
(ii)
(iii)
C (i)
(ii)
(iii)
(iv)
D (i)
(ii)
Inference
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
Conclusion
(Comment regarding the applications of emulsions as used in food preparation)
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
…………………………………………………………………………………………
Submit the activity for evaluation.
………………………………..
Counsellor Signature
132
PRACTICAL 8 FOOD COLOURS
Structure
8.1 Introduction
8.2 What are Natural or Synthetic Food Colours?
8.3 Characteristics and Structure
8.4 Permissible Level
8.5 Estimation of Synthetic Food Colours in Foods
Activity 1: Isolation of Various Synthetic Colours in the given Samples of Jams,
Squashes and Sauces
8.1
INTRODUCTION
Colour is an important constituent of food. You would recall studying in Unit 8 in the
theory course (MFN-008) that colour is an important attribute. It gives food an
attractive and appetizing appearance, and you would agree, also enhances the
acceptability of foods. Natural vegetative colours derived from beet root, chillies
(paprika), spinach, curcumin (turmeric), black grapes etc. are used in food and
pharmaceutical industry. Use of synthetic colours is also prevalent. However, the use
of synthetic colours in the food products comes to be looked upon with certain
amount of apprehension with regard to their safety. Many countries have restricted
the use of synthetic colours in food products. In this practical, we shall learn about
the various natural and synthetic colours in foods. The practical will equip you to
identify and isolate synthetic colours found in foods. You will become aware of the
permissible limits of the synthetic food colours.
Objectives
After undertaking this practical, you will be able to:
• describe the kind of natural and synthetic colours used in the food industry,
• recognize the permissible limits of the synthetic food colours,
• isolate the synthetic colours in various food products, and
• identify these synthetic colours.
8.2
WHAT ARE NATURAL OR SYNTHETIC FOOD
COLOURS?
Food in raw state has a natural colour, which is associated with the characteristics of
that food. In the processing, preservation and storage of some foods, this natural
colour is destroyed or modified and in some instances, off-flavour develops. The fact
that food colour is a very important factor in determining food acceptability has
stimulated the grocers and manufacturers of food to develop and make the best
possible food colours. These colours are frequently added to food processing or to
give the preparations the natural colour as expected. The need for colours arose
because some of the natural preparations such as jams, jellies, beverages tend to lose
their colour during the processing as the natural colours are sensitive to heat and light
or acidic or alkaline conditions. Certain mineral pigments like iron oxide, chrome
yellow, manganese brown, CuSO4 were also used to colour food. This give place to
synthetic dyes obtained from coal tar. Synthetic colours have the characteristics of
colour intensity, colour uniformity, colour stability and lower costs. Out of the
number of dyes (coal tar) available, only some are permitted for use in foods and are
called esterified food colours. These are water-soluble. However, a number of coal
tar dyes have been shown to be potent carcinogens therefore the use of coal tar dyes
as food additives is restricted. Synthetic colours form a major group of food colours
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which are classified into synthetic colour dyes and mineral pigments. These synthetic
colours are futher divided into acidic and basic dyes. Certain unpermitted colours
such as rhodamine B, blue VRS, Orange G are being used in foods and thus are of
great concern.
Natural colours consist of chlorophyll, carotenes, anthocyanins, flavones, annatto,
cochineal, saffron, turmeric, cardamom, betanin, safflower, caramel etc.
Let us study about the structure and characteristics of these natural and synthetic
colours next.
8.3
CHARACTERISTICS AND STRUCTURES
Look at the structure and the characteristics of some natural and synthetic colours
given herewith.
134
Amarnath
Amaranth is a dark reddish powder
slightly soluble in alcohol. HCl
(hydrochloric acid) does not change
the colour intensity of the solution.
NaOH (sodium hydroxide)
increases it.
Erythrosine
Erythrosine is a brown powder. It is
soluble in water and alcohol.
Reaction with HCl produces a
yellowish brown precipitate. NaOH
produces a rich precipitate soluble
in access of the reagent.
Indigo Carmine
Indigo carmine is a dark blue
powder, soluble in alcohol and
insoluble in organic solvent. Colour
of aqueous solution fades on
standing.
Tartrazine
Tartrazine is a bright-orange yellow
powder freely soluble in water. The
aqueous solution is not changed by
HCl but becomes redder with
NaOH.
Food Colours
Brilliant Blue
Brilliant blue FCF is reddish violet
powder/granules with a metallic
luster. It is soluble in water and
ethanol. It has pale amber solution
in conc. H2SO4, changing to yellow
then greenish blue on dilution.
Sunset Yellow (FCF)
Sunset yellow (FCF) is in the form
of orange-red crystals, soluble in
water. It forms reddish-orange
solution in conc. H2SO4, changing to
yellow on dilution.
Fast green (FCF)
Fast green (FCF) is dark green
powder, soluble in water and
ethanol. It forms dull orange
solution in conc. H2SO4 and bright
blue solution in 10% aqueous
NaOH.
Rhodamine B
Rhodamine B is a green crystal/
reddish violet powder. It is soluble
in water, soluble in alcohol and
slightly soluble in HCl and NaOH.
With a basic understanding of the characteristics and structure of the colours, we
move on study about the permissible level as recommended by PFA for their use in
foods.
8.4
PERMISSIBLE LEVEL
To regulate and enforce safety about the use of these synthetic colours and dyes PFA,
1954 has covered their use in part IV comprising of rules 23 to 31. Until 1968, 13
colours were allowed under the purview of the PFA Act. Subsequently, 5 colours
were withdrawn due to their toxic properties and 3 new colours were added in 1973
to make a list of 11 colours. At present, 8 colours are allowed mainly Carmoisine,
Ponceau 4R, Erythrosine, Sunset yellow, Tartrazine, Brilliant blue, Indigo Carmine
and Fast green.
The maximum permissible level of 200 ppm of food colour laid down in Rule 29 of
the PFA Act has been recently amended in 1995 to a level of 100 ppm in all the foods
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except for jams, jellies and canned foods in which the permissible level still remains
200 ppm.
As you are now familiar with the kinds and structure of synthetic colours and their
importance in food evaluation, let us therefore, study the process of estimation of
these colours in food.
8.5
ESTIMATION OF SYNTHETIC FOOD COLOURS IN
FOODS
Food colours in various products need to be isolated, identified and then
quantitatively measured for their limits. Estimation techniques for water soluble and
oil soluble colours vary. One can use the wool dyeing method for isolation of acidic
colours and can also use chromatographic techniques for their identification and
measurement.
To identify them, we must study the colour reactions of these water soluble, acidic
dyes which are characteristic to each colour and thus can be used as conformatory
tests. The reactions of various colours with different chemical medium are given in
Table 8.1.
Table 8.1: Reactions of various colours with different chemical medium
Name of the dye
Shade
Conc. HCl
Conc.H2SO4
10% NaOH
Liquor
Ammonia
(NH3)
Carmoisine
Violet
Little change
Deep violet
Red
Red
Erythrosine
Yellow red
Orange yellow
Orange yellow
No change
No change
Amaranth
Violet
Slightly darker
Violet
brownish
Dull brownish
to orange red
Little change
Tartrazine
Yellow
Slightly darker
Slightly darker
No change
No change
Sunset yellow FCF Orange
Slightly red
Redder
Brown
No change
Indigo carmine
Blue
Slightly darker
Darker
Greenish yellow Greenish blue
Rhodamine
Red
Colourless
Dark blue
No change
to
No change
The permitted colours should be checked for their limits through colourimeter. The
absoption maxima of various food colours is given in Table 8.2.
Table 8.2:Absoption maxima of various food colours
Name of the food colour
136
Absorption maxima (nm)
Amaranth
520
Fast red E
508
Carmosine
516
Ponceau 4R
507
Erythrosine
527
Green FCF
624
Indigo carmine
609
Green S
636
Brilliant blue FCF
630
Tartrazine
427
Sunset yellow FCF
482
Now, as you are aware about the structure and properties of various synthetic colours,
let us, in the activity given in this practical, carry out the isolation of various
synthetic colours in the given samples of jams, squashes, sauces and other preserves
and identify them according to given information. The given samples containing the
unpermitted synthetic colours would also indicate the positive adulteration.
Food Colours
ISOLATION OF VARIOUS SYNTHETIC COLOURS IN
THE GIVEN SAMPLES OF JAMS, SQUASHES AND
SAUCES
Aim: To detect the presence of synthetic food colours in the given samples.
ACTIVITY
1
Date: ………….
Objectives
After conducting this activity, you will be able to:
• describe the kind of natural and synthetic colours used in the food industry,
• recognize the permissible limits of the synthetic food colours,
• isolate the synthetic colours in various food products, and
• identify these synthetic colours.
Principle
Synthetic colours form a major group of food colours which are classified into
synthetic colour dyes and mineral pigments. These synthetic colours are futher
divided into acidic and basic dyes. The isolation is carried out with the wool dyeing
technique.
To identify them, you must study the colour reactions of these water soluble, acidic
dyes which are characteristic to each colour and thus can be used as conformatory
tests. The reactions of various colours with different chemical medium are given in
Table 8.1 earlier. Write down the reactions once again here in the format given:
Name of the
dye
Shade
Conc. HCl
Conc. H2SO4
10% NaOH
Liquor NH3
Carmoisine
Erythrosine
Amaranth
Tartrazine
Sunset yellow
FCF
Indigo carmine
Rhodamine
Materials Required
–
–
–
–
–
–
–
Pure white wool {defatted}
Sample (Jam, Squash, Sauce)
Glacial acetic acid
Ammonium hydroxide 2%
NaOH 10%
Solvent ether
NaCl 20%
–
–
–
–
–
–
–
Amyl alcohol
Conc. HCl and Conc.H2SO4
NH3 (Ammonia)
Separating funnels
Petri dishes
Glass rods
Beakers
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Procedure
Carry out the activity following the procedure enumerated herewith:
1) Preparation of the Sample
Before carrying out the isolation of acidic colours, it is necessary to remove the
interfering substances such as starches and fats, which hinder with the extraction
procedures. The pre preparation of the sample for the extraction process would
involve:
1) For Alcoholic drinks
Boil the alcoholic drinks to remove alcohol.
2) For the starchy products carry out the following steps:
Grind the starchy products like custard powders, cakes, pulses, candied fruits.
Treat 10 g of the ground sample with 50 ml of 2% NH3 in 70% ethanol.
Keep aside for one hour.
Centrifuge and take the liquid portion in a beaker.
Evaporate on the water bath.
Dilute the residue with 30 ml of dilute acetic acid.
3) For fatty food products like sausages, meats, fish pastes, processed nuts etc.
Defat the product with light petroleum in soxhlet apparatus.
Treat the defatted sample with 50 ml of 2% NH3 in 70% ethanol.
Keep aside for one hour.
Centrifuge and take the liquid portion in a beaker.
Evaporate on the water bath.
Dilute the residue with 30 ml of dilute acetic acid.
4) For the acidic products like fruit preserves and sauces
Solid samples are mixed with water and acidified with glacial acetic acid.
2) Dyeing of Wool
1) Immerse a 1m piece of pure white wool in the acidified solution of the
sample.
2) Warm the solution till the wool gets dyed.
3) Take out the wool wash in water.
4) Put the dyed wool in 25 ml of 2% NH4OH and boil it.
5) Add NH4OH in excess till the colour gets extracted and comes in the solution.
6) Take 24 ml of this aqueous solution add 6 ml of 10% NaOH and 30 ml of
solvent ether.
7) Take them in separating funnel, shake gently to mix all the layers.
8) Remove the aqueous fraction in another beaker.
9) To the ether layer add 5 ml of glacial acetic acid, if pink colour appears in the
ether layer, it indicates the presence of rhodamine.
10) Take the aqueous layer from the 8th step, add 10 ml of glacial acetic acid and
30 ml of ether. Shake well.
11) Remove the aqueous layer in separate beaker and to the ether layer add
excess of 10 ml of conc. NH4OH. If pink colour appears in the ether layer, it
indicates the presence of Erythrosine.
12) Take 25 ml of the aqueous layer, add 10 ml of 20% NaCl shake and add 30
ml amyl alcohol. Add excess of conc. HCl so that the total volume becomes
60 ml.
13) Remove the aqueous layer and to this add 30 ml ether. Shake. Pink colour
will appear in the water layer.
138
14) Remove the water layer and add 10 ml acetic acid. If the water layer is pink,
it indicates the presence of Amaranth. If it is orange, it indicates the presence
of Sunset yellow and if yellow, it may be Tartrazine.
Food Colours
Results and Observations
Record your observations as indicated herewith:
A) Product analyzed (Give the name of the product): ……………………………..
B) Sample Preparation steps
(Write down the steps followed by you in preparing the sample for analysis in the
space provided herewith):
C) Dyeing of wool
Colour observed-----------------------------Results of Extractions
Note your observations in the format given herewith:
Observations
S.No.
Extractions
1.
First (treated with NH4OH)
2.
Second
3.
Third
4.
Fourth
Aqueous fraction
Ether layer
Inference
The given sample of ……………… was found to contain ………………………
colour and thus could be regarded as adulterated/ non-adulterated sample.
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Conclusions
(Write briefly about the sample and the adulterant found in the sample, summing up
the activity).
…………………………………………………………………………………………..
…………………………………………………………………………………………..
…………………………………………………………………………………………..
…………………………………………………………………………………………..
…………………………………………………………………………………………..
Submit the activity for evaluation.
……………………………….
Counsellor Signature
140
PRACTICAL 9 PRESERVATION OF FOOD
Structure
9.1
9.2
9.3
9.4
Introduction
Food Spoilage
Principles of Preservation
Techniques of Preservation
9.4.1
9.4.2
9.4.3
9.4.4
9.4.5
9.4.6
Freezing
Blanching
Dehydration
Sulfuring
Canning
Preservation by Preservatives
Activity 1: Effectiveness of Blanching by Peroxidase Inactivity Test
Activity 2: Methods for Blanching Vegetables
Activity 3: Moisture Removal Techniques in Foods
Activity 4: Rehydration Test for the Dried Samples
9.1
INTRODUCTION
Food preservation is the process of treating and handling food in such a way as to
stop or greatly slow down spoilage to prevent food borne illness while maintaining
nutritional value, texture and flavour. Units 10, 11 and 12 in the theory course (MFN008) dealt exclusively with the concept, principles and techniques of food
preservation. Surely you must have gone through these units carefully and are well
equipped to conduct this practical which focuses on preservation techniques. We
suggest you look up these units once again now before you start with the activities
given in this practical.
Objectives
After undertaking this practical, you will be able to:
• carry out various methods of blanching,
• check the adequacy of blanching,
• appreciate the time–temperature relationship in food preservation,
• select an effective pre-treatment before any processing with maximum retention
of the sensory attributes and select the best method for further processing,
• adopt different drying techniques for food preservation,
• comment on the effectiveness of different drying techniques,
• select the best method of dehydration on the basis of various parameters such as
drying time and sensory characteristics of foods, and
• describe the sensory changes that take place during the dehydration of the
samples.
9.2
FOOD SPOILAGE
Food spoilage is a major concern of all people. Spoilage by growth of bacteria, yeasts
and moulds limits the time that the food can be stored and still be safe and palatable.
The environmental conditions optimal for reproduction vary with the type of these
microorganisms. Foods can be preserved by altering these so that they no longer
serve as a suitable host for microorganisms.
Foods also spoil when they undergo physical and chemical changes which may be
due to the action of enzymatic and non-enzymatic reactions such as oxidation,
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Principles of Food
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mechanical damage etc. Therefore, the major causes of food spoilage and
deterioration can be summarized as:
•
Biological
– growth of bacteria, yeast, mould
– activity of enzymes
– insects, rodents and parasites
•
Chemical
– reaction with oxygen
– chemical reactions within food constituents
– light
•
Physical
– temperature
– physical stress or abuse
Microbial spoilage readily occurs in foods having sufficient moisture and a
favourable temperature and other conditions of growth like pH, oxidation-reduction
potential. Thus, to hinder the growth of the microorganisms these conditions must be
taken care of and you would realize, this is the basis of food preservation. The next
section focuses on the principle of food preservation.
9.3
PRINCIPLES OF PRESERVATION
Various methods can be used for preservation of foods like freezing, pasteurization,
sterilization, canning, dehydration, use of preservatives and preservation by high
osmotic pressure.
All these techniques of food preservation involve the following principles of
preservation:
1) Prevention or delay of microbial decomposition.
a) By keeping out microorganisms (asepsis).
b) By removal of microorganisms e.g. by filtration.
c) By hindering the growth and activity of microorganisms e.g. by low
temperature,
drying, use of chemicals.
d) By killing microorganisms e.g. by heat, radiations.
2) Prevention or delay of self-decomposition of food
a) By destruction or inactivation of food enzymes e.g. by blanching.
b) By delay of chemical reactions e.g. use of antioxidant to prevent oxidation.
3) Prevention of damage caused by insects, animals and mechanical damage by
rodents etc.
Having learnt about the principle next let us study about the techniques of
preservation.
9.4
TECHNIQUES OF PRESERVATION
In the last section we have read that various methods can be used for preservation of
foods. Some of the common methods employed to preserve foods are summarized
herewith:
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•
Heat (blanching, pasteurization, sterilization...)
•
Cold (chilling, freezing etc.)
•
Drying (partial or fully)
•
Acid (fermentation, addition)
•
Sugar and salt (addition– osmotic effect)
•
Smoke (heat + smoke, formaldehyde and others)
•
Atmospheric conditions (O2 or CO2)
•
Radiation (X-ray, UV, microwaves, ionizing)
•
Chemicals (preservatives)
Preservation of Food
Since we have already studied about these methods in the theory course, let us
quickly review these methods (very briefly) here in this practical.
9.4.1 Freezing
This is a method of preservation using low temperature. The chief preservative effect
of freezing lies in the inability of microorganisms to grow at freezing or below
freezing temperature. Freezing can be carried out either by slow freezing process,
quick freezing process or dehydro freezing.
In vegetables, enzymatic action may still produce undesirable effects on flavour and
texture during freezing. The enzymes are thus destroyed by heating before the
vegetables are frozen. This is known as the process of blanching, about which we
shall discuss next.
9.4.2 Blanching
As described in Table 9.1, the enzymes in the food system can be separated into four
groups relating to the changes in flavour, colour, texture and nutritive value.
Table 9.1:Food quality related enzymes
S.No.
Quality
attribute
Enzymes
Quality defect
1.
Flavour
Lipoxygenases, Lipases
Off flavour development
2.
Colour
Polyphenol oxidases
Dark colour
3.
Texture or
consistency
Pectin methyl esterase, Amylase
Softness, loss in viscosity
4.
Nutritional value
Ascorbic
Thiaminase
Loss in Vitamin C and
loss in Vitamin B1 content
acid
oxidase,
The inactivation of these enzymes is dependent upon both the time and temperature
of heat treatment during the process of blanching. Peroxidase is the most heat stable
enzyme in plants and thus is taken as the “universal indicator” for checking the
adequacy of blanching for fruits and vegetables.
Blanching of vegetables prior to freezing and dehydration has some advantages, as
well as, disadvantages. The advantages include stabilization of texture, colour,
flavour and nutritional quality; removal of intercellular gases, reduction in microbial
load and shrinkage of vegetable matter which can aid in the achievement of required
fill weight. The disadvantages include loss of colour, flavour and nutritive value.
However, the disadvantages can be taken care of by optimizing the time and
temperature required for blanching.
9.4.3 Dehydration
The word dehydration usually refers to the use of controlled conditions of heating,
with the forced circulation of air/artificial dryer as compared to the use of sundrying. Dried foods have low available moisture level [low water activity (aw)] so
that the microorganisms cannot grow and enzyme activity is controlled. Water
activity refers to the amount of unbound or "free" water in a system available to
support biological and chemical reactions.
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Dehydration processes are used commercially for many foods including dried milk,
coffee, tea, fruit mixes, dried fruits, vegetables, meat, fish etc. Although the process
of drying lowers water activity (aw) so as to hinder the growth of microorganisms
however, this technique of preservation is also requiring certain pre-treatments like
blanching and sulfuring. You are already familiar with the term blanching (discussed
in sub-section 9.4.2). We shall learn about sulfuring in the next sub-section.
Here let us now look at the advantages of drying.
Advantages of drying
Drying has been attributed with advantages of weight reduction, ease of packing,
storage and transportation. However, loss of colour, texture and nutritive value has
also been observed in this process.
9.4.4 Sulfuring
Sulfuring is the process which is used to destroy microorganisms and to preserve
colour. Fruits after blanching may be dipped into a sulphite solution. This process of
sulfuring maintains colour of the food as it hinder the process of browning. Apples
and bananas are examples of fruits that retain their colour during the process of
drying if they are dipped in an acidic fruit juice or exposed to sulfuring which
minimizes browning.
Next, we move on to the canning process.
9.4.5 Canning
Canning involves the application of heat that is high enough to destroy all pathogenic
microorganisms and their spores present along with the air tight sealing in sterilized
containers. Canned foods can be stored at room temperature for at least a period of
2 years and still be safe to eat if they have been processed to be commercially sterile.
The processing of food before the process of canning would involve blanching,
filling the canned food with brine or syrup, exhausting, sealing and then heating.
Microbial spoilage in canned fruits and vegetables is due either to under processing
or leakage. Under processing is the failure to destroy during the heat process all
bacteria capable of subsequent growth in the product. Leakage is due to the
contamination of the product after an adequate heat process, either due to faulty seam
or damage to the can after sealing. It is very important to know the pH classification
of these fruits and vegetables so as to study their spoilage relationships. pH, we
already know, is a scaled measure of the acidity or alkalinity of a food: the lower the
pH, the higher the acidity.
Table 9.2 gives the classification of various fruits and vegetables on the basis of their
pH value.
Table 9.2: Classification of various fruits and vegetables on the basis of their pH value
S. No.
Class
pH range
Products
1.
Low acid
5.3 and higher
Vegetables such as corn, peas, lima beans,
cauliflower, potato, spinach, French beans and
beets
2.
Medium acid
5.3-4.5
Cabbage, turnip, pumpkin,
products like soups and sauces
3.
Acid
4.5-3.7
Tomato, pear, pineapple, banana, mango, apple,
jackfruit, peach and other fruits
4.
High acid
3.7 and lower
Sauerkraut, citrus juice,
pickles, chutneys etc.
Source: Adapted from Ranganna, 1999
Finally, let us learn about preservation by preservatives.
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carrot,
rhubarb,
okra,
prunes,
Preservation of Food
9.4.6 Preservation by Preservatives
Preservatives, as you may already know, belong to a class of food additives that
extend shelf life by inhibiting microbial growth, or by minimizing the destructive
effects of oxygen, metals, and other factors that may lead to rancidity. Common
preservatives include nitrites (used extensively in processed meats), sodium benzoate
(often added to soft drinks), sorbic acid (dairy products), calcium and sodium
propionates and sorbates (mould inhibitors used in baked goods) and common table
salt.
The preservatives generally used in fruit and vegetable products may be broadly
classified as class I and class II preservatives.
The class I preservatives are the natural preservatives which are not restricted in any
food. Examples of class I preservatives are common salt, sugar, dextrose/glucose
syrup, spices, vinegar or acetic acid and honey.
Class II preservatives are the chemical preservatives, which prevent or delay the
growth of microorganisms. However, the use of chemical preservatives is limited in
foodstuffs.
Table 9.3 summarizes some of these chemical preservatives generally accepted as
safe (GRAS) and their uses in various foods.
Table 9.3: Chemical preservatives generally accepted as safe (GRAS) and their uses in
various foods
S. No.
Preservatives
Maximum
Tolerance
Organism
Affected
Foods
1.
Propionic
acid/propionates
0.32%
Moulds
Bread, cakes, some cheeses,
rope inhibitor in bread dough
2.
Sorbic acid/
sorbates
0.2%
Moulds
Hard cheeses, figs, syrups,
jellies and cakes
3.
Benzoic acid/
benzoates
0.1%
Yeasts and
Moulds
Pickles, sauces, Ketchups,
salad
dressings
and
margarine
4.
SO2/sulphites
200-300ppm
Insects,
micro
organism
Molasses, dried fruits, wine
making
5.
Sodium diacetate
0.32%
Moulds
Bread
6.
Sodium nitrite
120 ppm
Clostridia
Meat-curing preparation
Source: GRAS, section 201(32) (s) of the U.S. Federal Food, Drug, and Cosmetic Act as
amended .
Commercially used natural preservatives are often used in preparation of jams, jellies
and pickles preparation. Water is withdrawn from microbial cells when they are
placed in solution containing large amounts of dissolved substances such as
sugar/salt. As a result of this water loss, microbial metabolism is halted and because
of this lower water activity, the microorganisms are not able to grow.
Food preservatives are often used in conjunction with other methods of preservation.
Now, with an understanding of the principles and various techniques involved in
preservation, let us carry out a few activities wherein we will be using these
techniques. There are four activities in this practical.
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ACTIVITY
1
Date: ………….
EFFECTIVENESS OF BLANCHING BY PEROXIDASE
INACTIVITY TEST
Aim: To test the effectiveness of blanching by peroxidase inactivity test.
Objectives
After undertaking this activity, you will be able to:
•
•
•
check the adequacy of the blanching process,
appreciate the importance of time–temperature relationship in blanching process,
and
select an effective pre-treatment before any processing with maximum retention
of the sensory attributes.
Principle
Raw or under blanched vegetables discolour, lose flavour and develop off flavours
during processing. The loss of quality is caused by enzymatic action. Peroxidase is
the most heat-resistant enzymes present in all vegetables. When these are inactivated
by heating, the enzymatic processes, in general would have been inhibited as other
heat resistant enzymes would have also been inactivated. Hence, blanched vegetables
should have been tested for their inactivation.
Materials Required
Green leafy vegetable
Other vegetable
0.08 % of peroxide solution H2O2: Dilute 2.8 ml of 30% H2O2 with water and store in
a dark bottle in a refrigerator. Prepare fresh every week
0.5 % Guaiacol in 50% ethyl alcohol
Stop-watch
Thermometers
Beakers
Pestle and Mortar
Test Tubes
Funnel
Cotton Distilled Water
Procedure
Carry out the activity following the procedure enumerated herewith:
1) Wash the given sample of vegetable thoroughly.
2) Dice or cut the vegetable.
3) Blanch small edible portions of vegetables at 85ºC, 100ºC for different time and
then carry out the following test for peroxidase activity.
4) After blanching put the vegetable immediately under cold water.
5) Take 10 g of representative sample.
6) Grind in a mortar using sand and 30 ml water added in small portions.
7) Filter through cotton cloth.
8) To 2.0 ml of filtrate, add 20 ml of distilled water in a test tube and mix.
9) Add 1 ml of 0.5 % guaiacol solution and then 0.08% H2O2 solution and keep
aside.
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10) Observe for the development of a brown ring.
11) If no brown ring formation takes place in 3–5 minutes consider the test to be
negative (i.e., inactive peroxidase test) and the product to be adequately blanched
Preservation of Food
Results and Observations
Record your findings in the format given herewith. With regards to sensory attributes
comment on the flavour, texture, and appearance of the vegetable sample. The
peroxidase activity, as observed through the presence of brown ring, may be
indicated under the column peroxidase activity.
S.No.
1.
2.
Vegetable
Name
Name
Blanching
tempºC
Time
(min.)
85
5
100
1
85
5
100
1
Peroxidase
Activity
active/inactive
Remarks
Sensory attributes
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Inference
Write the inference for the two samples:
A) The green leafy vegetable blanched at 85ºC gave peroxidase inactivity test at
……..………………… minutes.
When blanched at 100ºC, it gave peroxidase test at………………… minutes.
Out of the two temperatures, the maximum retention of sensory attributes was
found at ……………………… minutes and thus this time/temp would be
selected for further processing.
B) The ………….. vegetable blanched at 85° C gave peroxidase inactivity test at
…………… minutes.
When blanched at 100° C, it gave peroxidase test at………………………………
Out of the two temperatures the maximum retention of sensory attributes was
found at …………….. minutes and thus this time/temp would be selected for
further processing.
Conclusion
(Comment on the effectiveness of blanching of vegetables used)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
……………………………..
Counsellor Signature
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Preservation of Food
ACTIVITY
2
METHODS FOR BLANCHING VEGETABLES
Aim: To carry out various methods of blanching for the given vegetables.
Date: ………….
Objectives
After undertaking this activity, you will be able to:
• carry out various methods of blanching, and
• select the best method for further processing.
Principle
Blanching and cooling are necessary steps in the processing of vegetables. Blanching
is a partial pre-cooking treatment in which vegetables/fruits are usually heated in
water or in steam before processing. There are many ways of blanching, depending
upon the type of vegetable and the products desired.
The main purpose of blanching before processing is to inactivate enzymes, remove
raw and bitter flavour, stabilize the colour, stabilize the texture, reduce bacterial load
and add desirable additives.
Various methods are employed for blanching of vegetables such as hot water
blanching, steam blanching, microwave blanching with water spray or air cooling or
a combination of these.
Materials Required
Samples of vegetables to be blanched
Metallic Sieves
Microwave
Petri dishes
0.08% peroxide H2O2: Dilute 2.8 ml of 30% H2O2 with water and store in a dark
bottle in a refrigerator. Prepare fresh every week
0.5% Guaiacol in 50% ethyl alcohol
Stop-watch
Thermometers
Beakers
Pestle and mortar
Test tubes
Funnel
Cotton
Distilled water
Filter paper
Procedure
Now carry out the activity following the steps enumerated herewith:
1) Wash the given sample of vegetable thoroughly.
2) Dice or cut the vegetable.
3) Divide the sample into six parts.
4) Expose the first portion of the vegetable to hot water blanching by dipping the
vegetable in water having the temperature of 100° C. Note the time and carry out
peroxidase activity test as given in activity 1. Select the time where the
peroxidase activity is negative.
5) Repeat step 4 with the second portion. In this, the sample should be air dried after
blanching. Carry out the peroxidase test as in activity 1.
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6) Place third portion of the vegetable on a sieve and carry out the process of
steaming and cooling in cold water. Note the time and conduct peroxidase
activity test.
7) Do the steaming of the fourth portion of the sample along with air cooling of the
sample. Select the time where the peroxidase activity is negative.
8) To the fifth and sixth portion, do microwave blanching along with water and air
cooling respectively. Note for each, the time for peroxidase inactivity.
Results and Discussions
Record your observation in the format given herewith:
S. No.
1.
2.
Vegetable
Blanching
Time taken
(min)
Cooling
First portion
Hot water
Water
Second
Hot water
Air
Third
Steam
Water
Fourth
Steam
Air
Fifth
Microwave
Water
Sixth
Microwave
Air
First portion
Hot water
Water
Second
Hot water
Air
Third
Steam
Water
Fourth
Steam
Air
Fifth
Microwave
Water
Sixth
Microwave
Air
Peroxidase
activity
Remarks
Inference
From the above results, it was found ………………… vegetable, when blanched
with ………………… and cooled by ………………… gave best results in terms of
colour, flavour and texture retention.
From the above results, it was found ………………… vegetable, when blanched
with ………………… and cooled by ………………… gave best results in terms of
colour, flavour and texture retention.
Conclusion
(Comment on the blanching methods used for and peroxide different vegetables
taken)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
……………………………….
Counsellor Signature
150
Preservation of Food
ACTIVITY
3
MOISTURE REMOVAL TECHNIQUES IN FOODS
Aim: To carry out the moisture removal in foods by different drying techniques.
Date: ………….
Objectives
After undertaking this activity, you will be able to:
• make yourselves familiarized with different drying techniques, namely sundrying, tray drying and microwave drying, and
• select the best method of dehydration on the basis of various parameters such as
drying time and sensory characteristics of foods.
Principle
The principle of removal of moisture from food includes the process of heat and mass
transfer. Factors increasing heat and mass transfer are larger surface area, greater
temperature difference between the heating medium and the food, higher velocity of
air, dry air, low pressure drying process that employ high temperature for short time
do less damage to food than drying process employing lower temperature for longer
time.
Commercially, various drying processes are in use as air convection driers, cabinet
driers, tray driers, fluidized bed driers, spray driers, drum driers, vacuum drier, freeze
drier etc. However, due to limitation of equipment we will be using three processes
of drying. These are:
• Sun drying
• Tray drying
• Microwave
Materials Required
Sample material
Sieves
Filter paper
Tray dehydrator
Microwave
Muslin cloth
Procedure
Carry out the activity following the steps enumerated herewith:
1) Wash the vegetable thoroughly.
2) Dice vegetable into small pieces.
3) Divide the vegetable into six parts.
4) Keep the first part in the tray dehydrator at 70-75°C.
5) Conduct the blanching of the second portion according to previous activity. Air
dry on filter paper for half an hour and keep in the tray dehydrator at 70-75°C.
6) Keep the third portion after washing for sun dry.
7) To the fourth portion, do blanching and keep for sun drying.
8) Keep the fifth portion in the microwave.
9) To the sixth portion, do blanching and keep in the microwave for drying.
10) Note the change in colour, flavour and texture of all the portions after drying.
11) Keep them for shelf life analysis.
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S.
No.
Results and Observations
Observe the samples for the sensory attributes (like colour, texture, flavour, overall
appearance) and report under remarks column of the observation table given
herewith.
Weight of
the
vegetable (g)
Blanched/
unblanched
Drying
technique
used
Weight of
the dried
sample (g)
Remarks
1.
2.
3.
4.
5.
6.
7.
For shelf life analysis, the sample should be observed after one month for any
changes in the sensory attributes.
Inference
The vegetable dried by …………………. method gave in the best results in terms of
………………………………………………………………………………………..
Conclusions
(Comment on the different drying techniques used to carry out moisture removal in
sample).
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
………………………………
Counsellor Signature
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Preservation of Food
REHYDRATION TESTS FOR THE DRIED SAMPLES
Aim: To perform the rehydration tests for the dried samples prepared in activity 3.
ACTIVITY
4
Date: ………….
Objectives
After undertaking this activity, you will be able to:
•
•
gain knowledge about the sensory changes that take place during the dehydration
of the samples, and
learn about the effectiveness of different drying techniques.
Principle
Rehydration tests for the dried materials are important as they give idea about the
percentage water in the rehydrated material, rehydration ratio and coefficient of
rehydration. However, no standard method for testing these are available, although
are developed by the plants where the daily evaluation of quality of dried products is
made.
Materials Required
Sample: Culture or dehydrated carrots or dehydrated cauliflower or dehydrated
cabbage. (Take any 3 dried sample).
Beakers – (6)
Distilled water
Filter paper
Burner
Funnel
Weighing balance
Petri dish
Procedure
The following procedure for measuring rehydration is suggested by the US
Department of Agriculture. Follow these steps and carry out the activity.
1) Weigh 2-10 g of the dry material (sample) in six beakers of 500 ml capacity.
2) Add 80-150 ml of distilled water*
3) Cover each beaker with watch glass, bring to a boil within 3 min on an electric
heater/burner and continue boiling for 5 minute.
4) Filter through whatman no. 4 filter paper and drain excess water until the drip
from the funnel has stopped.
5) Remove the sample from the funnel and weigh in a weighed petri dish.
6) Set the sample aside for conducting quality tests.
7) Rehydrate six other 10 g samples, boiling two for 10 minutes, two for
20 minutes, and two for 30 minutes.
8) Boiling should be carried out carefully for proper rehydration of samples.
9) Now record your observations and do the calculations as stated herewith.
*Note: You would notice that the precise amount of water which will actually go into
rehydrating the given sample, will vary with material, time and rate of
boiling
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Calculations
1) Rehydration ratio- If the weight of the dehydrated sample is x g and the drained
weight of the rehydrated sample is y g then rehydration ratio is calculated as:
Ratio being
x:y
2) Coefficient of rehydration:
d X [100 – b]
Coefficient of rehydration = ------------------------[a – c] × 100
where,
d = Drained weight of rehydrated sample
b = moisture content of sample before drying
a = Weight of dried sample taken for rehydration
c = Amount of moisture present in the dried sample taken for rehydration.
(Calculation of moisture present is a lengthy and time consuming process.
We shall hence not go into the process here. For calculation purposes, we
will however take the value 8-10%).
3) Percent water in the rehydrated material
Percent water in the rehydrated material is calculated as:
[d − x] ×100
d
where,
d = drained weight of rehydrated sample
x = dry matter content in the sample taken for rehydration
Precautions
1) The precise amount of water will vary with material, time and rate of boiling.
2) Start the test with at least enough water to submerge the pieces, but do not use so
much water that excess amounts are present at the end of the test.
3) Shake or stir, if necessary, to ensure wetting of all pieces during the test.
4) Control the rate of heating so as to prevent rapid and variable losses of water
while boiling.
Results and Observations
Record the observations of the experiment conducted by you in the space given
herewith. Start with naming the sample.
Sample Name ………………..
Next, calculate the rehydration ratio and coefficient of rehydration for this sample.
1) Rehydration ratio =
X =
Y =
Ratio is :
d × [100 – b]
2) Coefficient of rehydration = ------------------------[a – c] × 100
d = …………………..
b = …………………..
a = ………………….
c = 8-10%
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Putting into the formula, we have coefficient of rehydration as:
Preservation of Food
3) Percent water in the rehydrated material is calculated as:
[d – x] × 100
---------------d
d = ………….
x = ………….
Percent water is calculated as:
Now, do the calculations for all the dried samples as done for the first sample
Note the results in the table given herewith:
Sample (name of
the vegetable)
Rehydration
ratio
Coefficient of
rehydration
Percent
water
Time taken for
rehydration
Inference
The time taken for rehydration is ………………….
The rehydration ratio is …………………………..
The coefficient of rehydration is …………………..
Conclusion
(Comment on the comparative drying techniques for rehydration of the products).
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
………………………………
Counsellor Signature
155
PRACTICAL 10 NEW PRODUCT
DEVELOPMENT
Structure
10.1 Introduction
10.2 What is Product Development?
10.3 Product Life Cycle
10.4 Factors Affecting Development of a New Product
10.5 The Process of Development
10.6 Future Trends
Activity 1: Conduct the Market Research for Various New Products Available
Activity 2: Development of a New Product
10.1
INTRODUCTION
Unit 14 in the theory course (MFN-008) covered the important area of product
development and evaluation. We studied why it is important to develop new products
and also about the concept of functional foods in this unit. A detailed discussion on
the ingredients providing health benefits and their use in speciality foods was also
presented. Geared with this knowledge now we hope you are ready for developing a
new product on your own. That is what the focus of this practical is. You will find
some basic information related to new product development also included in this
practical which will actually get you started with this interesting activity of new
product development.
Objectives
After conducting the various activities included in this practical, you will be able to:
• enlist the various new products available in the market,
• identify the ingredients and the novel techniques involved in new product
development,
• discuss the packaging and labeling requirements of different products,
• explore new ideas and concept of development of a process,
• determine the factors affecting the process of development, and
• explain the concept of shelf life of food products.
10.2 WHAT IS PRODUCT DEVELOPMENT?
Life cannot be sustained without adequate nourishment and foods of different types
and in different forms are consumed to provide this very nourishment. Today, the
consumers are much aware and expect better choices to be available. Changed life
styles have led to the development of new products and improvement of current
products. There is an increased demand for higher added value and product
performance creating novel technologies for the design and development of food
products.
Increased application of technologies from other areas such as engineering,
agriculture marine resources has also contributed to large and continuous production,
for new preservation method for a large variety of ingredients and for new food
products.
We can say that development of a new product is a continuous process and is also
required owing to:
1) Change in consumer preferences
2) Price advantage
3) Increased shelf life
156
4) Convenience
5) Nutritional awareness
6) Demand for specific foods – food targeted towards specific demographic groups
such as diabetic foods, reduced fat and fat-free items and foods for specific health
requirements.
New Product
Development
Ideally a new product is defined as “development and introduction of a product not
previously manufactured by a company into a market place or presentation of an old
product into a new market not previously explored by a company”.
The development of a product can be in terms of:
1) Line extension
2) Repositioning of existing product
3) Reformulation of existing product
4) New packaging of an old product
5) Innovative or creative products
Let us learn about the product life cycle next.
10.3 PRODUCT LIFE CYCLE
wth
Maturity
In
t ro
du
ct
io
n
Gr o
ne
cli
De
Life Period
Every food product passes through different phases throughout its life and therefore,
the need for development of a new product arises. Each product shows introduction,
growth, maturity and decline during its period of existence. The various stages of
product life cycle are shown in Figure 10.1.
Production
Figure 10.1: Product life cycle
Let us review these phases in the product life cycle one by one.
1) Introduction phase
The introduction phase, as is evident in Figure 10.1, marks the launch of the product
in the market.
2) Growth phase
Once the product crosses the introduction phase, it enters the growth phase.
Generally, about 95% of the products fail at the introduction phase. Thus, a mere 5%
are able to enter the growth phase. The growth phase involves strategy of product
modification, enlarging distribution and maintaining a competitive price level. The
strategy also involves one of extending product to different use situations and
considering newer packaging alternatives to attract more and more new customers.
3) Maturity phase
Maturity phase is characterized by slowing of growth of sales and profits, as depicted
in the Figure 10.1. It also sees a boom in the market demand as more and more
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customers are now willing to accept the product. This phase is also marked by strong
competition.
4) Decline phase
Decline phase, as is evident from Figure 10.1, is the phase when sales decline
because customer preferences have changed in favour of more efficient and better
products. Customer’s value perception of the product also undergoes a change. It
leads to the gradual withdrawal of the product from the market.
So we start with the introduction phase and the product moves through the whole
cycle to reach the decline phase. Next, what are the factors, which affect the
development of a new product? Look up sub-section 14.2.1 in Unit 14 in the theory
booklet for information on these factors. We have also highlighted these factors here
in the next section.
10.4 FACTORS AFFECTING DEVELOPMENT OF A NEW
PRODUCT
The product development and marketing is not just selling a product, but is a highly
multi-disciplinary domain comprising of technology, management, packaging
specialized product positioning, regulation, advertising, promotion, distribution,
infrastructure support, pricing and customer feedback.
The product should create an image that is consistent with what it can deliver to
consumers. The right image is most essential to match consumer’s expectation from
the product.
Some elements that must be considered for product development are listed below:
•
Emerging trends: recognizing trends as they emerge, a number of demographics,
social and economic factors must be reviewed.
•
Product quality, including taste and texture: the product design must conform to
the expectation of the consumers with regard to its sensory qualities.
•
Flawless execution: even the best product will fail if positioning, packaging or
marketing is flawed or inefficient.
New product development is a proactive process. Products should be fully
conceptualized before actual product development is undertaken. The industry not
only has to take care of the sensory attributes like appearance, taste, aroma of the
product but also has to look into the important issues of manufacturing, retailing and
marketing along with the development. Research and development of any
organization plays a pivotal role. Research and development involves a broad
spectrum of activities of planning, organizing, developing and offering reactive, as
well as, proactive solutions.
The main function of Research and Development in the food processing operation is
the development of new products, which can contribute to overall profitability of an
operation. The main factors to be considered in evaluating proposed projects include:
•
•
•
•
•
•
•
•
•
•
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Feasibility
Historic Background
Approach and timing
Cost of project
Compatibility with company’s objectives
Patent position
Market potential
Availability of raw materials
Estimated investment to capitalize and estimating returns
Sales promotion required to introduce a new product
•
•
•
•
•
Legal problems
Distribution channels
Operational and microbiological hazards involved
By-product utilization
Competitors aspect
New Product
Development
With a brief review of the factors, let us now study the actual process involved with
the development of any product.
10.5 THE PROCESS OF DEVELOPMENT
Figure 10.2 shows the process of new product development in the form of a flow
chart. As is evident, the process of development starts with the idea generation stage
followed by idea screening, concept development and testing to marketing strategy
development and finally to product development. Let us look at these processes.
IDEA GENERATION
IDEA SRCEENING
CONCEPT DEVELOPMENT & TESTING
MARKETING STRATEGY DEVELOPMENT
FEASIBILITY ANALYSIS
PRODUCT DEVELOPMENT
MARKET TESTING
CONSUMER REALIZATION OF PRODUCT
Figure 10.2: The process of new product development
1) Idea Generation
The process of new product development starts with the search for new ideas. The
common sources of new product ideas being:
•
•
•
•
Customer expectation
Estimating market demand through market research
Competitors
Research journals and magazines
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•
•
•
•
Seminars and conferences
Research and development scientists
Media
Top management
Idea generation is a stage characterized by creativity. It not only involves getting the
product idea but also the concept development and product image should be
hypothesized.
After the idea is generated, we move on to the idea screening process. Let us see
what this process involves.
2) Idea Screening
Idea screening involves the acceptance of formulation of the idea by doing cause and
effect analysis. This stage usually identifies the success and failure factors in
different product ideas. It requires strong decision making and usually involves the
top authority. After the idea is screened, the concept is developed and tested.
3) Concept Development and Testing
A concept is an elaborated version of the product idea. The concepts are developed to
the extent of the new product satisfying consumer needs, the price strategy involved
for positioning of the product in the market, purchase intentions at a given price level
and so on. This exercise of concept building helps to face and understand the
situations better and is a proactive approach.
4)
Market Strategy Development
Market strategy development would require the study of the markets for potential
consumers. It would also involve the study of the market for existing products and
their moving sale volume, product positioning and identifying the test markets.
Next is the feasibility analysis.
5) Feasibility Analysis
Once the product concepts have been formed, the feasibility studies are conducted.
This study involves the following:
1) Estimation of demand in the target market at different price levels.
2) Forecasting sales based on demand estimation and competitive analysis.
3) Cost benefit analysis.
4) Calculation of the break-even point and sales volume.
Once the product concept seems feasible, the firm now takes the concept to the next
stage of product development.
6) Product development
The product development involves various stages of development. The stages being:
a) Studying the ingredient characteristics
b) Technique standardization
c) Variations
d) Product standardization
e) Product development
f) Sensory evaluation/consumer acceptance
g) Product modification
h) Final product
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The development of the product involves vigorous functional and consumer tests.
Functional tests are performed under laboratory and field situations to test the
product feasibility. Consumer testing involves various sensory evaluation tests to
study consumer acceptance.
7)
New Product
Development
Market Testing and Commercialization
The new products are tested in the markets on four parameters: trial, first
purchase, adoption, frequency and volume. This test marketing can be done on
the pilot or small scale level. Once the test marketing is completed and the firm
has favourable results, it is then ready to commercialize the product. The process
of commercialization includes timings, place and strategy for marketing and
distribution.
Product positioning in the market can determine the success or failure of
products.
We have reviewed the various process involved in the new product development
in our discussion above. You will find this information useful when you get
down to developing a product.
Finally, let us study about the future trends.
10.6 FUTURE TRENDS
There are many major aspects that will sway the future trends in the development
of new products. In the new millennium predominant factors would be
continuous growth in productivity at farm, as well as, processor level,
competitiveness and economic survival, consumer needs and conveniences,
socioeconomic changes, buying power and continued evolution of market tasks.
Future technologies have to be based on promptness, cost, easy methodology and
efficiency. It requires use of both innovative approach and operational approach.
What are these approaches? Let’s find out.
Innovative approach
This would involve lot of research and development to come up with newer ideas
and technology.
Operational approach
It has been defined as the application of scientific methods, technology and tools
to operation of system with optimum solution to the problem. It is based on
identification of objectives, constraints or bottlenecks, controllable and
uncontrollable factors and the role of authority entrusted with power of decision
making.
The future trends emphasize on nutrition, freshness and convenience and thus
these need to be addressed in the design of innovative products. This change in
scenario for product development has moved organizations and companies
involved in formulating foods for health benefits into new areas of understanding
like health risk, risk, benefits analysis, evaluation of efficiency and toxicity and
health regulation.
A number of different terms have been used to describe the many natural
products currently being developed for health benefits. These include
nutraceuticals, functional foods, pharma foods, designer foods, vita foods,
phytochemicals etc. What are functional foods? Do you recall studying about
them in sub-section 14.5.1 in the Unit 14 in the theory booklet (MFN-008)? We
suggest you look up the section now.
Functional foods are similar in appearance to conventional foods and are
consumed as a part of the usual diet but have demonstrated physiological benefits
and thus reduce the risk of chronic diseases beyond basic nutritional function.
A nutraceutical is a product produced from foods but sold in the form of pills,
powders and other medicinal forms and has demonstrated to have a physiological
benefit or provide protection against chronic diseases.
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The close alliance of nutritional knowledge and the delivery of promised benefits
in food products offer an unparalleled opportunity to developing a product mix
that is basis of good health. The most emphatic trend in new product
development in the last decade has been in the area of special dietary products.
Current trends indicate the development of sports of performance drinks,
nutritionally enriched beverages such as vitamin fortified drinks, fruit juices,
juices added with proteins and even herbal extracts.
In India, traditional products will continue to influence demand in the future.
These food products have an established market. Consumers demand better
quality of packaged traditional products with longer shelf life. The rich Indian
traditional knowledge base is an asset, in fact an intellectual property, which
needs to be preserved and shared to benefit of human kind.
In India, much of the traditional knowledge is documented in ‘Wealth of India’
published by Council of Scientific and Industrial Research, the initiative has
already been taken by Government towards creating a functional Traditional
Knowledge Digital Library (TKPL) a traditional medicinal plants and systems,
which would provide updated information on medicinal and therapeutic
properties through computer. The TKPL is expected to lead the Traditional
Knowledge Resource Classification (TKRC) system, which would be linked, to
the International Patent Classification (IPC) system. This would help to bridge
the gap between ancient knowledge and modern technology.
The development of products to confer a health benefit is a relatively new brand
and recognizes the growing acceptance of the role of diet in disease prevention
and treatment. Thus, the new product concept that would appeal to new age
consumers seeking health benefits from production, would also pave the way for
future research and development and technology development endeavours.
With this, we end our discussion on product development. We hope this
information will guide you in carrying out the two activities included in this
practical. So get started.
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New Product
Development
ACTIVITY
CONDUCT THE MARKET RESEARCH FOR VARIOUS
1
NEW PRODUCTS AVAILABLE
Aim: To conduct the market research for various new products available.
Date: ………….
Objectives
After undertaking this activity, you will be able to:
• recognize the various products available in the market,
• assess the consumer demand,
• identify the ingredients and the novel techniques involved in product
development,
• appreciate the packaging and labeling requirements of different products,
• acquire knowledge about the shelf life of the product, and
• categorize the products into different areas.
Market Research
Market research is an exhaustive process and serves as a guide to familiarize one
with the data collection methods, research methodology and forecasting techniques.
Market analysis covers various aspects related to market and products such as market
size, market growth, market segments, products available, product demand,
technology used, product life cycle and cost dynamics. In organizations, market
research is an integral part of the product development. Only after conducting market
research, the organizations plan their strategies for product formulation and
marketing. Market survey or research is the only way by which companies can study
consumers and their behaviour. The market research of any organization may address
the following questions:
What kind of product they are planning to put out?
Which market segment they actually target?
What is the market potential of the product or service?
Who are the competitors?
What are the market strategies of the competitors?
What are the customer expectations?
How to project new product or service more attractive for the customer by means of
value addition?
This activity has been designed with a view to give you an idea about the markets,
various products available, the brands available, consumer reactions and
expectations, the target customer, the cost factor involved, the packaging and labeling
requirements of the products.
Methodology
Conduct a survey for various products available in the markets.
Categorize the product according to:
1) Technologies involved, like frozen products, dehydrated products, products
involving high concentration of sugars or salt, canned products, thermally treated
products, products having preservatives or products with combined techniques.
2) Groups the products according to food groups, like milk and milk products,
cereals and cereal products, fruits, vegetable products, fats and oils, sugars, meat
and meat products.
3) Purpose they serve, example, ready-to-eat products, functional foods,
convenience products, ready- to- serve products, pre-processed or semi-processed
products.
4) Consumption pattern as breakfast preparations, meal preparation, snacks,
desserts, accompaniments and beverages.
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After the categorization of the products, the following information should be noted:
• Name of the product
• Technology involved
• List of ingredients
• Brands available
• Packaging
• Label and information on the label
• Shelf life of the product
Results and Observations
Report the information collected in the format given on page 165.
Conclusions and Inference
Number of products surveyed …………………………………………
Products listed in the following categories
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Product information available
Conclusions
(Comment on the new products available in the market)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation
……………………………..
Counsellor Signature
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New Product
Development
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ACTIVITY
2
DEVELOPMENT OF A NEW PRODUCT
Date: ………….
Aim: To develop a new product from the given product ingredient.
Objectives
After undertaking this activity, you will be able to:
• explore new ideas for product development,
• understand the concept of development of a process,
• gain knowledge about a technique,
• determine the factors affecting the process of development,
• explain the concept of variations, and
• appreciate the packaging and labeling requirements of the product developed.
Methodology
The process of development of the product in laboratory would involve:
1) Study of the ingredient characteristics
2) Idea generation
3) Feasibility
4) Technique standardization
5) Variations
6) Product standardization
7) Product development
8) Sensory evaluation
9) Product modification
10) Final product
11) Label design and Packaging
Important considerations for the process of development
The process of development would involve exploration of various ideas for example,
if the product ingredient provided is Soya, one need to study the product
characteristics first like it being a rich source of proteins and fat. And also that as it is
having low moisture content it can be ground, or made in powdered form.
Thus, the product ideas can be of types:
Soya powder, or paste used in the formation of: Soya flakes
Soya papad
Soya biscuits
Soya granules can be used for:
Namkeen preparation
Or any other snack preparation (can be
used as filling or in the base product)
Soya milk can be extracted and products such as shrikhand, sweets, paneer, butter
can be prepared.
However, it should be kept in mind that the given ingredient should be the basic or
major ingredient in any product formulation.
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One should also see the kind of infrastructure available in the laboratory and use the
techniques which can be easily standardized for example, if it is not possible to carry
out the controlled fermentation process one should avoid doing so.
New Product
Development
While doing variations in the product formulation, only one variation should be done
at one time so as to attribute the results to a single factor. For example, if you are
adding soya flour and channa flour to wheat flour at the same time, the resulting
hardness or softness of the dough prepared could be because of any of these. Thus, to
know the property of each you have to add one at a time and that to in different
proportions.
Standardization of a method can be achieved by the use of standard weights and
volume of ingredients. These standards for weights and volumes of different
ingredients and dishes can be established by use of scales, slicing machines,
measuring equipment, standard spoons, scoops and ladles designed to hold a
measured amount of weight or volume of the food.
Sensory evaluation should be conducted at each stage of development so as to assess
the acceptance of the product on the basis of appearance, taste, texture, consistency
or viscosity, mouthfeel etc. Various tests for sensory evaluation can be made use of.
These tests have already been described in Practical 6. Look them up once again.
Packaging and labeling: The final product should be properly packed and labeled
and then only the assessment of shelf life should be carried out. The packaging of the
product should be based on the product characteristics and the availability of the
packaging material. Also, the study of packaging material of the similar products
available in the market as carried out in activity 1 of this practical can be made use of
for designing of the packet.
Label for the product should be carefully designed and should hold the following
information:
1) Name of the product
2) Product ingredients in the right order
3) Vegetarian/non vegetarian mark
4) Total weight of the product
5) Nutritional information
6) Any specific use of the product
7) Product catering to any specific group of people
8) Observed shelf life
9) Storage conditions required
10) Directions for use, if any
11) Cost of the product
Product cost: Cost of the product would include:
1) Ingredient cost/food cost.
2) Cost of process like any blanching done, dehydration etc.
3) Labour cost generally taken as 10-15% of the food cost.
4) Overheads like any non food material used for processing, packaging and
labeling cost.
5) Profits can vary from 15-50%.
Now, keeping the important considerations highlighted above in mind, get down to
developing the new product.
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To help you with this, we have included one example here of how to go about
developing a new product. We have taken the example of “Bajra Crunchies”. Read
the process given here carefully and then in the same manner develop your new
product.
Name of the product – Bajra Crunchies
Selection Criteria/ importance of selecting the product*
Biscuits are one of the most common bakery products eaten all over the world. They
are the most easily available ready-to-eat energy dense food for both rich and poor.
Although liked by all ages, they are not very popular because of the empty calories
they provide. Biscuits can be made more nutritious by using a varied ingredient mix
which would add to its value. Thus, the present product is developed keeping in mind
the health awareness among Indian consumers and their demand for a whole product,
which is rich in fibre and other nutrients. Therefore, to increase the nutritive value of
biscuits, Bajra and Wheat bran were added making them iron and fibre-rich.
Basic recipe for Biscuit Preparation
Amount of Ingredients
Refined Flour- 50 g , Butter- 25 g, Castor sugar- 30 g, Baking powder ¼ tsp
Method of preparation
1) Sieve the flour and baking powder together.
2) Cream butter and sugar together till light and fluffy.
3) Add flour to the above mixture and make the dough.
4) Roll out the dough on a floored board into ¼ inch thickness.
5) Cut into shapes and prick each biscuit with a fork.
6) Baked on greased baking tray in a moderately hot oven for 10-15 minutes or till
golden brown in colour.
7) Remove and cool on a wire rack.
Variations carried out
S. No.
1.
Variations
Observations
Technique variations
No technique variation was carried
out. The addition of ingredients did
not require any pre processing.
2.
Sensory evaluation/
remarks
……..
Ingredient variations
Biscuits were prepared using various
ingredients as refined flour, bajra,
wheat bran.
Weights (g)
Refined flour 30
25
20
15
Bajra
20
15
20
20
Wheat bran
0
05
10
15
Total weight 50
168
50
50
50
The ingredient mix
gave different result.
It was observed that
the biscuit prepared
with even low weight
of refined flour could
be prepared and the
dough prepared was
smooth.
When the biscuits were
evaluated on the sensory
scale. It was observed that all
the biscuits had golden brown
colour and smooth texture.
However, less of refined flour
in the last variation and more
of bran provided crunchier
taste and thus was chosen for
preparation.
New Product
Development
As these high fibre biscuits would
cater to a class of people who are
health conscious, thus a low-fat and a
low-sugar substitute was also tried
out.
2.
Change in the amount of fat used
Weight (g)
3.
Refined flour 15
15
15
15
Bajra
20
20
20
20
Wheat Bran
15
15
15
15
Butter
25
20
15
10
Castor sugar
30
30
30
30
Baking powder ¼
¼
¼
¼
The biscuits prepared
with less of fat say 10
g of butter were
showing cracks
during the process of
rolling.
When evaluated on the sensory
scale, it was observed that all the
variations had a pleasant flavour but
the 4th variation showed less brown
colour formation during the process
of baking. Even when tasted, these
biscuits were very hard.
The 3rd variation had less fat was
also liked on the sensory scale and
thus was selected for further
development.
The dough prepared
from each variation
was smooth for
preparation of
biscuits.
When sensory evaluated even a
smaller proportion of sugar say 10 g
was giving appropriate sweetness in
the high fibre biscuits. Thus this
preparation was used for final
product prepared.
Change in the proportion of sugar
used for preparation of biscuit
Here, in this ingredient variation we
not only lowered down the amount of
sugar but also added a pinch of salt to
improve the flavour and taste of sugar
Weight (g)
R. flour
15
15
15
15
Bajra
20
20
20
20
Wheat bran
15
15
15
15
Butter
15
15
15
15
Castor sugar
30
25
15
10
Salt
a pinch
¼
¼
Baking Powder ¼
¼
Note: The sensory evaluation is to be done in terms of appearance, colour,
flavour, texture etc.
Standardized recipe
The ingredient mix for the final product (70 g) standardized was:
Refined flour :
15 g
Bajra :
20 g
Wheat bran:
15 g
Butter :
15 g
Castor sugar:
10 g
Salt:
a pinch
Baking powder:
1/4 tsp
*Milk :
5 ml
*As the fat content was decreased, a little milk was added to make smooth
dough.
The preparation of the product was carried out in the same manner as indicated in
the basic recipe.
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MAIDA
Sieve It
Process flow of the prepared product
Ingredients used are: Maida, Bajra, Bran, Butter, Sugar, Salt and Baking Powder
The process flow chart for developing the bajra crunchies is given herewith:
BAJRA
BRAN
Sieve It
BUTTER
SUGAR
BAKING
POWDER
SALT
Sieve It
Sieve It
CREAM
BUTTER &
SUGAR
ADD SALT
MIX ALL INGREDIENTS &
MAKE A SMOOTH DOUGH
(ADD MILK IF REQUIRED)
ROLL & CUT INTO BISCUITS
WITH THE HELP OF BISCUIT
CUTTER
PLACE ON GREASED
BAKING TRAY FOR 30
MINUTES
REMOVE AFTER COOLING
Cost Calculation
Food cost = Rs. 4.03
Ingredients used and their costing:
S.No.
Ingredients
Cost/ kg
(Rs)
Amounts
used
Cost in product
(75 g) (Rs)
1.
Refined Flour
24
15
0.36
2.
Bajra
20
20
0.40
3.
Wheat Bran
20
15
0.30
4.
Butter
150
15
2.25
5.
Castor sugar
22
10
0.22
6.
Salt
A pinch
0.1
7.
Baking powder
160
¼ tsp
0.25
8.
Milk
15
10 ml
0.15
Total cost = 4.03
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Cost of process like baking =15% of food cost = Rs.0.60
*Labour cost (self etc.)
New Product
Development
= 20% of food cost = Rs. 0.81
Overheads cost (Packaging, space, equipment etc) = 20% of food cost
= Rs. 0.81
Profits
=15% of food cost = Rs.0.60
Total cost for 75 g biscuits would be
= Rs.(4.03+ 0.60+ 0.81+ 0.81+ 0.60)
= Rs. 6.85 ≈ Rs. 7.00
*Here, we have 20% labour cost as the product is involving more of the manual
work. However, in industries all the cost go down because of the machinery used
and bulk production. Thus, they have more profit margins.
Nutritive value for 75 g pack of biscuit is as follows:
Ingredients
Amt.
(g)
Energy
(Kcal)
Proteins
(g)
CHO
(g)
Fat
(g)
Fibre
(g)
Iron
(mg)
Calcium
(mg)
Refined flour
15
52
1.65
11
0.1
0.04
0.4
3.45
Bajra
20
72
2.39
13.5
1.0
0.24
1.6
8.4
Wheat bran
15
----
---
---
----
15
----
2.25
Butter
15
73
---
---
8.1
---
---
---
Sugar
10
40
---
10
--
---
---
---
Milk
10
1
----
---
0.1
---
---
2.1
238
4.0
34.5
9.3
15.3
2.0
16.20
Total
Packaging and labeling of the product
Packaging of biscuits involves both the primary and secondary packets. These
primary package should be laminated paper which should have wax paper (oilproof ) and moisture-proof paper, so that there is no absorption of moisture from
the atmosphere which will make the biscuits soggy i.e they tend to loose their
crispness. The secondary packing is normally used to further protect the biscuits
from moisture absorption, breakdown etc. It is also used as a print media for all
the labeling information required.
Labeling
The labeling of the pack should include the following:
• Green dot indicating the Vegetarian mark.
• List of ingredients in the proportion of use as for this pack these would be:
bajra, refined flour, wheat bran, butter, sugar, milk and baking powder.
• Weight of the product= 75 g.
• Cost of the product which is the MRP= Rs. 7.00.
• Nutritional information per 75 g : as indicated in the table above.
• Date of manufacturing.
• Shelf life or best before say 6 months after the date of manufacturing.
• The product can have its own brand name or logo such as Bajra crunchies:
a natural way to good health.
Now, as you are familiar with the steps of product development, let us start with the
activity 2. Fill in the information or observations in the format given herewith ( you
can refer to the above listed example)
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ACTIVITY
2
DEVELOPMENT OF NEW PRODUCT
Date: ………….
Name of the product -------------------------------------------Selection Criteria/ importance of selecting the product Comment on the
importance/relevance/nutritive value/cost effectiveness/ convenience of the selected
products any basic recipe/technique used for development
Process flow of the prepared product (give the flow chart of the steps involved)
172
Variations carried out
S.No.
Variations
New Product
Development
Observations
Sensory evaluation/
Remarks
Technique variations
Ingredient variations
Note: The sensory evaluation is to be done in terms of appearance, colour,
flavour, texture etc.
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Standardized recipe
(write the recipe including the ingredients used )
Cost calculation
Food cost =
Ingredients used:
S.No.
Ingredients
Cost/ kg
Amounts used
(Rs)
Total cost =
Cost of process like any blanching done, dehydration etc. =
Labour cost (self etc.) =
Overheads cost (mention the items included) =
Profits =
Total cost/ …………… g =
Nutritive value of the product per …………… g
Ingredients
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Total
Amt.
(g)
Energy
(Kcal)
Proteins
(g)
CHO
(g)
Fat
(g)
Cost in
product (Rs)
Packaging and labeling of the product
New Product
Development
Photographs of the stages of product development/ final product
Inference and Conclusions
(please remark on the sensory evaluation of the final product conducted)
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
Submit the activity for evaluation.
……………………………..
Counsellor Signature
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