Food Chemistry
FD-203
(3+1)
Fall Semester 2020
Second Year Food Engineering
Batch 2020
Lecture 3
Dr Muhammad Badaruddin
mbadaruddin@cloud.neduet.edu.pk
Course Content
• Chemical Composition of Foods:
Carbohydrates, proteins, lipids, water, vitamins, minerals,
phenolic compounds and pigments.
• Food Additives:
Preservatives, colorants, antioxidants, sweeteners, emulsifiers.
• Toxicological concepts:
Contaminants and evaluation of metals, radionucleides, plant
protective agents, hormones, antibiotics mycotoxins,
polycyclic aromatic hydrocarbons and toxic compounds
naturally found in foods.
• Nutritional value of food:
Calorific value and pH of food.
Lipids
• Lipids comprise a broad group of chemically diverse compounds
that are linked together by the fact that they are all soluble in
organic solvents.
OR
• Lipids are formed from structural units with a pronounced
hydrophobicity.
• Lipids are soluble in organic solvents but not in water.
• Food lipids are generally referred to as fats (solid) or oils (liquid),
indicating their physical state at ambient temperatures.
• Some lipids are surface-active since they are amphiphilic molecules
(contain both hydrophilic and hydrophobic moieties). Hence, they
are polar and distinctly different from neutral lipids.
• The majority of lipids are derivatives of fatty acids.
• The two approaches generally accepted for lipid classification are
presented in Table 3.1.
Lipids
Lipids
Lipids
Triglycerides
Esters of fatty acid and glycerol
R’, R’’ and R’’’ are hydrocarbon chains
Triglycerides are abundant form
Mono- and Di- glycerides
Mono- glycerides
Emulsifying agent
Di- glycerides
Types of Triglycerides
Fatty acids
• The major components of lipids are the fatty acids that
contain an aliphatic chain with a carboxylic acid group.
• Most natural fatty acids have an even number of carbons
due to the biological process of fatty acid elongation
where two carbons are added at a time.
• The majority of fatty acids in nature contain 14–24
carbons.
Types of Fatty acids
Fatty acids are generally classified as either saturated or
unsaturated, with the latter containing double bonds.
Types of Fatty Acids
Saturated Fatty Acids (SFA)
Unsaturated Fatty Acids
Analysis on the basis of health aspects
PUFA
MUFA
SFA
Analysis on the basis of stability
SFA
MUFA
PUFA
Properties of Fats and Oil
1. Solubility
• Soluble in organic solvent.
• Insoluble in water
Properties of Fats and Oil
2. Effect of heat
a. Slip Melting point: a point at which fat stars to melt.
b. Smoke point: point at which fat or oil produces smoke or blue haze.
c.
Flash Point: temperature at which oil starts to ignite.
Properties of Fats and Oil
3. Plasticity
If force is applied beyond elastic limit, substance cannot retain its original
shape (i.e. deform permanently), it is called plasticity.
Plasticity means property of spreadibility here.
Properties of Fats and Oil
4. Rancidity
Development of unpleasant odour or flavour.
Reason for food deterioration of food with lipid content.
Two type of rancidity.
a. Oxidative rancidity
b. Hydrolytic rancidity
Properties of Fats and Oil
5. Saponification and saponification value
Lipids in presence of alkali produces soap.
Soap is a mixture of salts of different fatty acids.
Saponification value is the amount (mg) of alkali (NaOH,
KOH etc) required to produce soap from 1gm of fat/oil.
• Saponification value tells the nature of fatty acid in
lipids.
Properties of Fats and Oil
6. Iodine number
Gives the information about unsaturation..
Uses of lipids
1. Energy
2. Basic ingredient of adipose tissue.
3. Used in frying
4. Used as shortening