biochemistry of food

1. Biochemistry of
food

2. Food:
Any substances that can be metabolized by an organism to give energy
and build tissue, as
(Carbohydrates, Proteins, Fats, Oils, Vitamins, Minerals and Salts).

3. Vitamins:
Essential organic compounds to ensure proper metabolism with little caloric value.
• Several diseases are associated with vitamin deficiencies
enter directly
into
bloodstream
must be
transported by
carrier proteins

4. • Milk has a Complex Nature, it is considered as a solution, an emulsion, and a colloidal dispersion with
normal pH is about 6.6 and contains about 87% water.
• Composition of Milk: Contains all major nutrients
1. Water – 87%
2. Protein - 3.5%
3. Fat - 3.5%
4. Carbohydrates - 5%
5. Vitamins and Minerals

5. • Casein 1. Whey
• 80% of milk protein
• Micelles: cluster of molecules found
in colloidal dispersions Make milk
white
• Curds: Casein clumps that separate
from the liquid
• When pH is lowered to 4.6, casein
breaks down, coagulates, and turns
to curds
• heat has little effect on coagulating
casein
•
 20% milk protein
 Protein found in
liquid that remains
after fat and casein
have been removed
from milk
 also called serum
protein
 heat easily
coagulates whey
—
•Milk contains Two Main Proteins:

6. — Emulsion — Creaming — Cream
Small globules of lipids
are dispersed throughout
water.
Fat droplets come together
in clusters that rise and
float to top of milk.
Milk that is extra rich in
emulsified fat droplets.
Milk Fat
• Milk is an emulsion.
• Micelles are clusters of molecules that occur within the colloidal dispersion and
globules vary in size and have a thin membrane around them.
• Milk fat contains very little cholesterol Fats influence flavor, texture, and price
(more fat usually equates to more costly milk).

7. 3. Carbohydrate:
Lactose or milk sugar is the main carbohydrate present in milk.
When milk is heated, reacts with amino acids in protein to produce Maillard reaction, turns a golden
brown color and slightly caramel flavor.
• Lactose intolerance: Inability to digest milk due to the absence of the lactase enzyme in intestines
3. Minerals & Vitamins: Natural salts prevent milk from curdling. Trace elements in milk are
(Cobalt, Copper, Iodine, Iron, Magnesium, Nickel and Molybdenum).
• Vitamins in milk are (Riboflavin, Thiamin, Niacin and Vitamin A). Riboflavin breaks down
when exposed to light.

8. • Processing of Milk:
1. Pasteurization – heating raw milk to high temps to
destroy bacteria, then cooled.
2. Homogenization – breaking up milk fat into smaller
globules which disperses them permanently, eliminates
creaming
3. Fortification – adding nutrients to food (Vitamin D
and Vitamin A).

9. • Types of Milk:
1. Raw - unpasteurized milk straight from the cow.
2. Fluid Milk – classified by fat content (skim, 1%, 2% and whole).
3. Ultrahigh-Temperature Milk (UHT) – special processing can be stored without refrigeration up to 3 months.
• 3- Concentrated Milk:
• - Evaporated milk: canned whole milk concentrate with 60% of water removed.
• - Sweetened condensed milk: 50% of water is evaporated and sugar is added.
• 4- Cream – classified according to fat content (half & half, light whipping cream and heavy whipping cream).
• 5- Dry Milk – water is removed leaving dry solids

10. • Cultured milk products:
1. Culture – controlled bacterial population that is added to milk.
2. Inoculation – starter is added to the milk to start the growth of bacteria.
3. Incubation period – time bacteria has to grow and ferment the milk
• Ex. - Sour cream: cream that has been soured by lactic-acid bacteria.
- Yogurt: made by fermenting skimmed milk with special acid-forming bacteria.
- Buttermilk: made by adding bacteria to milk.

11. • Storage of Milk
• Closed container protects flavor
• Opaque container protects riboflavin
• Canned milk: cool, dry place
• Dry milk: cool dry place
• Freezing milk changes consistency