Question

1. How does pasteurisation affect the casein proteins?

2. How does pasteurisation affect the whey proteins?

3. How are the monosaccharides derived from the hydrolysis of lactose fed into the glycolytic pathway? Do not show structures, but clearly describe the molecules and intermediates involved!

4. What is the primary reason for lactose intolerance?

5. What is the fate of lactose in lactose intolerant individuals?

6. Provide i) a description of the results observed when milk was treated with buffers at different pH values.

Include in your answer ii) a conclusion about the mechanism of pH dependent precipitation of milk proteins and

iii) the biochemical composition of the precipitate and supernatant.

Answer 1

1)High temperature short time pasteurization will not affect functional and nutritional properties of casein protein. High temperature affect functional properties.Scalded milk is the milk has been heated to 82°C. At this temperature bacterias are killed enzymes in the milk are destroyed, whey protein denatures first as compare to casein protein.

2)Whey proteins are denatures proteins mainly whey proteins :are of two types alpha - lactalbumin, beta-lactoglobulin become denatures. The thiol group of beta-lactoglobulin is exposed and bind with another exposed thiol group. This results in irreversible denaturing. Casein structure miscell not changed.

3)Lactose is a disacchride present milk composed of glucose and glactose. Glactose only differ from glucose its sterochemistry at one position, but must be enters into glycolysis (first lactose converted into pyruvate then pyruvate converted into glucose 6 phosphate then glucose 6 phosphate to glucose.

4)Primary reason of lactose intolerance is deficiency of lactase enzyme. Due to deficiency of lactase enzymes causes bacterial ferment, this results in formation of gases and acids. Causes irritation in stomach.