Product Testing During
Prototype Development
How do you know you are on the
right track??
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Testing Products
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Gives you data to play with, data with which to make
decisions on what to do next
However collecting data is not a lot of use on its own
Testing needs a context and to have a purpose. The
student must need to find out something they don’t
already know, prove something they suspect or collect
information to justify a decision
Needs other information to make interpretations.
Students will need a background in the chemistry and
microbiology of their product as well
Choosing a test is half the battle.
Tests can be comparative rather than absolute if you
can’t access the correct equipment
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Instrumental Testing
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Cost effective
Reliable, repeatable, valid
Easy and quick to do if the technique and
equipment is available
Reduces amount of sensory testing with
trained panels
Can correlate to trained panels
Texture, rheology, colour, physical properties
are the most common
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Product Testing – General
Guidelines
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Always have a aim for the test and a way ot
use the data
Conduct tests as appropriate to help explain
what is happening
Obtaining consistent samples is most
important
Define samples precisely so comparisons can
be made during the development process
Establish test conditions and stick to them
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Volume
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Seed displacement
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Use a cylinder/box larger than the sample to
measure the volume of solid food products based
on seed displacement
Cake can be measure in tins after baking to look at
amount of volume increase
Index to volume
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Take a cross section from the sample and trace, or
photocopy or use a planimeter
Examine increase or decrease in size
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Specific Gravity
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A measure of density of food in relation to
water
 Weigh a given volume of sample and divide by
the weight of the same volume of water
(1 ml = 1 gm @ 4oC)
 Example specific gravity of potatoes for
waxiness of potatoes. In a brine solution (1
part salt/11 parts water) waxy potatoes
(boiling) float and non-waxy (floury) sink
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Moisture
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Press fluids
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Apply controlled pressure for a controlled time.
Good for meats and fish
Sample is weighed before and after and the
difference is the amount of juice in the sample
Wettability
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Baked products can be tested this way
Weigh sample and place in dish of water for 5 secs
then weigh again
High moisture products have good wettability and
are likely to score high for moistness in a sensory
panel
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Moisture (1)
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Drying oven
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Weigh sample and dry in a low oven until no more
weight loss occurs
Difference is calculated as a percentage of
moisture
Initial weight-final weight/initial weight x 100
Karl Fischer titration
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Food homogenised at high speed to release water
then titrated until the water has all reacted.
Fast but costly and you need the machine
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Water Activity
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An important measure for microbiological
activity in non-sterile foods
 Amount of available moisture in a product.
 1/100th of the relative humidity of the food
expressed at a %. ie Vapor pressure of water
divided by that of pure water at the same
temperature.
 Pure water is 1.0. Anything above 0.85 is a
problem for food safety
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Texture (1)
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Warner-Bratzler shear
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Shear press
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Used to measure meat
Force required to shear a core of meat
Need to control standing time and temp of coring
Compresses extrudes and shears at the same time
Good for fruit and veges
Compressimeter
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Measures compressibility not shear
Good for porous baked goods
Apply pressure until sample is deformed a specific amount
and determine the force to do that. The greater the force the
firmer the product
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Texture (2)
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Penetrometer
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Tenderness of food. Uses a plunger with a needle or cone
Allowed to penetrate the product (gravity) for a set period of
time then the distance is measured. The larger the distance
the more tender the product
Good for gels, instance puddings and some baked goods
Bloom gelometer
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Special type of penetrometer
Shot is added until the plunger has moved a set distance into
the product
The amount added is a measure of the tenderness of the
product
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Texture (3)
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Percent sag
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Shortometer
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Tenderness measurement of a gel
Depth of the sample is measured in a container, sample is tipped out
and depth measured again
Percentage sag is calculated. Higher the % the more tender the
product
Cookies and crackers
Force applied until the sample snaps. Softer the product the lower
the force required
Instron Universal testing machine
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Has several different test devices to measure different food
characteristics
Cohesiveness, adhesiveness, hardness, springiness, gumminess,
chewiness and fracturability
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Texture (4)
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Farinograph
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Texturometer
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Measures and depicts gluten development
duirng mixing of batters and doughs
Measures similar properties to the instron
but simulates chewing actions
Masticometer
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Approximates chewing actions
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Rheology
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The flow of matter and the deformation that results
from that flow
Viscosity the ability of a fluid to develop and maintain a
shearing stress and offer resistance to flow
A top plate moving one speed and a bottom plate
moving a slower speed the speed of the fluid in the
middle is the shear rate
Viscosity normally decreases with increasing
temperature
Fluids are Newtonian – viscosity independent of shear
rate or Non-Newtonian- rate alters with shear stress
Newtonian – sugar syrups and wine
Non-Newtonian – emulsions, chocolate and tomato
paste
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Viscosity Measurement
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Consistometer
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Line-spread test
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Set of concentric rings with column in centre
Column lifted and sample left to spread for up to 2 mins.
Measure taken at 90o increments and a mean determined
Amylograph
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Bostwick or Adams for semi-solid foods
Bostwick flow in specified time in the slating trough and
Adams is spread in a specified time
Used for starch pastes
Viscometers
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Rotational or capillary actions
Brookfield measures the drag on various sizes of spindles at
certain speed thru the sample
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Influences on Colour Measurement
Light source
 Sample characteristics
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Opaque, translucent or transparent
 Chemical
 Physical
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Smoothness of surface
 Refractive index of the food
 Particle size
 Geometric impact
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Colour Measurement
Various measuring devices can be used
to obtain values in a number of the
notations
 Munsell produces a book of the colours
in their notation
 We can set up our own systems using
paint charts
 Use liquid chromatography to separate
the colours in a product
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Cell Structure
Photocopy
 Photographs – don’t just take the item
cut it in half as a record
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Chemical and Microbiological
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Vital to check for food safety and label claims
and nutrition information
 Helps to understand the impact of
processing/packaging on the product and
therefore improve development decisions
 Tests are numerous; pH, Aw, moisture
content, fat content, vitamin C, total plate
count etc
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Chemical Methods
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Nutrient Analysis
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pH
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pH meters or papers
Most food pH 7 less than 7 acidic more than 7 alkaline
Need to work out format to test food in
Sugar concentration
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Various tests to determine nutrient content
Titrations for level of vitamin C, Iodine for starch and so on
Have a chat to the chemistry teacher and see what they can do for you
Refractometer to determine sugar concentrations
Light refracted thru sugar solutions to give degrees Brix (% sucrose in
solution)
Can also use a hydrometer
Saltiness
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Use flame photometry
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Chemical Methods
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Aroma
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Flavour
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Electronic nose
Gas chromatography to define the volatiles
in the product
Proximate analysis
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Moisture, ash, protein, fat and fibre are
commonly tested for
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Microbiology
Samples of food can be tested for levels
of microbiological contamination
 Normally two steps; level of presence
and then identification
 Students will stay mostly at the first level
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