Principles of food Preparation
Milk and Beverages
Effect of heat on milk→
-Heating of milk can be damaging to the nutritional value of the drink.
- It impact on milk may cause development of hypoallergenic milk.
- Heat effect various nutrients and aspects of milk :
I. Protein
II. Fat
III. Acid
IV. Minerals
V. Vitamins
VI. Color , flavor , digestibility
VII. Microorganisms
A. Protein:
a. On heating , Lactalbumin and Lactoglobulin become
insolubile or precipitated.
b. Lactalbumin begins to coagulate at a temperature of 66°C
& almost total when whey proteins are heated at 90°C for
5 minutes.
c. For whey protein , heat denaturation is an irreversible
reaction .
d. The amount of coagulation increases with increase
temperature and time of heating.
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, e. The coagulum forms appears as small particles rather than
firm mass and collects on the bottom of the pan in which it
is heated.
f. The protein found in largest amount in the milk is Casein. It
does not coagulate at usual temperatures .
g. Casein coagulates at
100°c for 12hours
135º c for 1 hour
155°C for 30 minutes
h. The resistance of casein to heat is because it is in combination
with a definite amount of Calcium , magnesium , phosphorous
and citrate of milk.
B. Fat :
a. The layer of fat that may form on milk that has been boiled.
b. It results from the breaking of proteins that surround the fat
globules in the unheated milk
c. The breaking of films of emulsifying agents permits the
coalescence of fat globules.
C. Acid :
a. When milk is heated , its acidity decreases at first because of
the release of dissolved carbon dioxide.
b. Then the acidity increases because hydrogen ions are free
when calcium and phosphate forms insoluble compounds.
c. A balance between these opposing factors prevents large
changes of pH during heating.
D. Minerals:
a. The dispersion of calcium phosphate of milk is decreased by
heating and part of it is precipitated.
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Page
Milk and Beverages
Effect of heat on milk→
-Heating of milk can be damaging to the nutritional value of the drink.
- It impact on milk may cause development of hypoallergenic milk.
- Heat effect various nutrients and aspects of milk :
I. Protein
II. Fat
III. Acid
IV. Minerals
V. Vitamins
VI. Color , flavor , digestibility
VII. Microorganisms
A. Protein:
a. On heating , Lactalbumin and Lactoglobulin become
insolubile or precipitated.
b. Lactalbumin begins to coagulate at a temperature of 66°C
& almost total when whey proteins are heated at 90°C for
5 minutes.
c. For whey protein , heat denaturation is an irreversible
reaction .
d. The amount of coagulation increases with increase
temperature and time of heating.
1
Page
, e. The coagulum forms appears as small particles rather than
firm mass and collects on the bottom of the pan in which it
is heated.
f. The protein found in largest amount in the milk is Casein. It
does not coagulate at usual temperatures .
g. Casein coagulates at
100°c for 12hours
135º c for 1 hour
155°C for 30 minutes
h. The resistance of casein to heat is because it is in combination
with a definite amount of Calcium , magnesium , phosphorous
and citrate of milk.
B. Fat :
a. The layer of fat that may form on milk that has been boiled.
b. It results from the breaking of proteins that surround the fat
globules in the unheated milk
c. The breaking of films of emulsifying agents permits the
coalescence of fat globules.
C. Acid :
a. When milk is heated , its acidity decreases at first because of
the release of dissolved carbon dioxide.
b. Then the acidity increases because hydrogen ions are free
when calcium and phosphate forms insoluble compounds.
c. A balance between these opposing factors prevents large
changes of pH during heating.
D. Minerals:
a. The dispersion of calcium phosphate of milk is decreased by
heating and part of it is precipitated.
2
Page
