Water, Carbohydrates, Proteins, and Fats and Oils are major constituents of food. Different foods have different percentages of these constituents. Water is the major constituent although it provides no energy. It plays a very important role in food spoilage as it provides a medium for many chemical, biochemical and microbial reactions. Carbohydrate and Proteins though same amount of energy they have very different role in human body. Carbohydrates provide energy to body and brain and good for GUT. Proteins on the other hand make muscles, skin, hairs, nails. In short supportive and protective structure, enzymes, antibodies, blood, etc are made up of protein. Fats provide double the amount of energy as compared to carbs or protein. They make our food delicious and form an adipose layer beneath the skin. Video of this presentation is available at https://youtu.be/z9XC0Y-DoZM

2. Water
• Water is present in three forms
• Free water,
• Physically bound water
• Chemically bound water

3. Free Water
• Free water is available for chemical
and biochemical reactions
• Used by microorganisms
• Can be frozen or removed

4. Physically Bound Water
• Forces that binds are of physical
nature
• This type of finding is found in
emulsions, gels, etc

5. Chemically bound water
• Involves chemical linkages of water molecules to
various constituents such as carbohydrates and
salts
• Difficult to remove during drying
• Difficult to separate during freezing
• Reduce availability for chemical and biochemical
reactions
• Reduce availability for microbial activity depends
upon its degree.

6. Equilibrium Relative Humidity
• The relative humidity of the atmosphere at a particular temperature
at which a material neither gains nor loses moisture.
• Relative humidity of the air surrounding the food that is in
equilibrium with its environment.

7. 0-25% ERH,
• Water is unfreezable
and
• food is stable
• Auto-oxidation may
occur
25 – 80%
• Freezing point is
reduced
• Food is liable to
deteriorative changes:
i.e. non-enzymatic
browning, hydrolytic
and oxidative
reactions
80 – 99%
• Reduction in freezing
point of tissue
• Growth of
microorganisms
• Enzymatic activity
• Oxidative and
hydrolytic reactions
• Non-enzymatic
browning

8. Nature of Food Dispersions
• A mixture in which fine particles are scattered in a continuous phase
throughout a different substance or state
• The part which is dispersed is known as the dispersed phase and is
suspended in the continuous phase.

9. Food
Solutions
Dispersions in which solid
or semi-solid particles are
evenly distributed in
water

10. Colloidal
Solutions
• A mixture in which the substances are
regularly suspended in a fluid.
• Long chain macromolecules consisting of
aggregated molecules of proteins,
polysaccharides, lipids, etc
• Example
• Jam, jellies, ketchup

11. Food Gel
• Consist of a continuous phase of
interconnected particles intermingled
with a continuous water phase
• Various degree of rigidity, elasticity, and
brittleness depends upon gelling agent
• E.g.: cornstarch, gums, pectin, etc

12. Emulsion
• Two immiscible liquid are dispersed
• It has two phases
• Dispersed phase
• Continuous phase
• Food emulsions normally consist of
water and a plastic lipid such as oil, fat,
wax, etc
• Oil-in-water : cream, milk, mayonnaise
• Water –in-oil : butter, margarine, etc

13. Importance of
Water
• Essential for chemical reactions in a living
organisms
• Governs the rate of chemical reactions
• Act as a reactant in hydrolytic reactions
• Serve as a transport medium; carry nutrients to
the cells and remove waste
• Percentage of water and state in which it appears
is important in determining the storage life of a
food

14. Carbohydrates

15. Carbohydrates
Monosaccharides Oligosaccharides Polysaccharides

16. Monosaccharides
• Simplest form of sugars
• Can not be hydrolysed
• Sweet in nature
• Soluble in water
• Supply energy
• Crystallize when water is
evaporated
• Prevent microorganisms growth in
high concentration
• Fermented by microorganisms
• Caramelize on heating
• Browning reactions; combine with
proteins to give dark colour

20. Starch
• Not sweet
• Readily soluble in cold water
• Form pastes and gels in hot water
• A reserve energy source in plant
• Starch paste are used to thicken food
• Starch granules in heated water swell and
gelatinize, and finally form a paste on
cooling

21. Cellulose and hemicellulose
• Abundant in plant kingdom and act as
supporting structure
• Insoluble in water
• Not digested by man so do not yield
energy
• Important in food as dietary fiber

22. Pectin and Gums
• Made up of sugar acids
• Found in fruits and vegetables (between cell walls)
• Soluble in water
• In colloidal solutions contribute to viscosity
• In solution form gels
• Added to food as thickeners and stabilizes
• Gum arabic

23. Protein

24. Protein
• Made up of long chains of amino acids held by peptide bond
C
CH3
NH2
H
COOH
Amino group
R
Carboxylic Acid

25. C
CH3
H
C-OH
O
C
CH3
H
C-OH
O
C
CH3
H
C-OH
O
C
CH3
H
C
O
H
+H2O
Peptide Bond Formation

26. • Essential to all life
• Form supporting and protective structures
• Cartilage, skin, hair, nails and muscles
• Major constituents of
• Enzymes, antibodies, hormones, milk,
blood and egg white

27. 20 amino acids
Essential amino acids
• Leucine
• Isoleucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Valine
• Histidine
Non-essential amino acids
• Alanine
• Arginine
• Aspartic acid
• Cystine
• Cysteine
• Glutamic acid
• Glycine
• Hydroxyproline
• Proline
• Serine
• Tyrosine

28. Types of proteins
Proteins
Primary Secondary Tertiary Quaternary

31. Fats and oils
• Not polymers of repeating units
• Do not form long molecular chains
• Smooth, greasy substance
• Insoluble in water
• Fuel source

32. Structure
• Glycerol combined with three fatty acids
• 20 different fatty acids

33. • Oil is a fat that is liquid at room temperature
• Saturated Fatty Acids: no double bonds
• Unsaturated Fatty Acids: one or more double bonds
• Hydrogenation: hydrogen is added to saturate the unsaturated
fatty acids
• Smoke Point: start producing smoke
• Flash Point: further heating produce flash
• Burning Point: temperature at which burning starts

34. Properties
• Soften on heating; do not have a sharp
melting point
• Brown the surface of foods as they can be
heated above boiling point
• Become rancid when react with oxygen
• Form emulsions with water
• Act as a lubricant
• Shortening power; tear protein and starch
structures
• Contribute characteristic flavour
• Produce a feeling of satiety and loss of
hunger