ICAR AIEEA-PG Milk Proteins & Enzymes: practice questions

1 · Caseins: alpha-s1, alpha-s2, beta and kappa · easy

Which casein contains no cysteine and has five phosphate groups clustered near its N-terminus?

1. Alpha-s2-casein
2. Alpha-s1-casein
3. Beta-casein
4. Kappa-casein

2 · Casein micelle structure and models · medium

Why is the submicelle model no longer favoured?

1. It assumed micelles contain fat, which analysis disproved
2. It could not explain why micelles contain colloidal calcium phosphate, magnesium and citrate at all
3. High-resolution microscopy and scattering studies have not shown discrete submicelles
4. It placed kappa-casein at the core, contradicting rennet action

3 · Genetic polymorphism of milk proteins, including A1 and A2 beta-casein · medium

Which peptide is released more readily from A1 than from A2 beta-casein during digestion?

1. Valine-proline-proline
2. Caseinomacropeptide
3. Lactoferricin
4. Beta-casomorphin-7

4 · Genetic polymorphism of milk proteins, including A1 and A2 beta-casein · medium

In goats, the alpha-s1-casein gene has strong, weak and null alleles. What is their main technological effect?

1. They change the amount of alpha-s1-casein secreted, with large effects on cheese yield and curd firmness
2. They determine whether goat milk contains beta-lactoglobulin
3. They change the colour of goat milk from white to yellow by altering carotene transport into the milk fat
4. They control the size of fat globules and the rate of creaming

5 · Genetic polymorphism of milk proteins, including A1 and A2 beta-casein · medium

Which milk is predominantly of the A2 beta-casein type?

1. Milk from a herd of A1A1 Holstein cows
2. Buffalo milk
3. Milk from an A1A2 heterozygous herd
4. Milk of any cow fed on pasture

6 · Immunoglobulins, lactoferrin, lysozyme and lactoperoxidase · easy

Lactoferrin inhibits bacteria mainly by:

1. Binding iron so that bacteria cannot use it
2. Lowering the pH of milk below 4.6
3. Hydrolysing bonds in bacterial cell walls
4. Oxidising thiocyanate to hypothiocyanite

7 · Enzyme indicators of heat treatment · medium

In the Aschaffenburg turbidity test, a filtrate that stays clear on boiling shows that the milk:

1. Contained no remaining native whey protein, as in sterilised milk
2. Contained added water or skim milk powder
3. Was adequately pasteurised at minimum HTST conditions but not sterilised
4. Was raw, with all whey proteins still native

8 · Bioactive peptides and protein hydrolysates · medium

If 0.9 milliequivalents of peptide bonds per gram are cleaved in casein (h-total 8.2 milliequivalents per gram), what is the degree of hydrolysis?

1. 9.1 per cent
2. 11.0 per cent
3. 0.11 per cent
4. 10.2 per cent

9 · Milk protein allergenicity · medium

Why do many children with milk allergy tolerate milk baked into foods but react to fresh milk?

1. Baked foods contain no milk protein after cooking
2. Heating destroys many conformational whey protein epitopes
3. Baking removes lactose, the cause of allergic reactions
4. Baking converts all casein epitopes into harmless amino acids

10 · Classification of milk proteins and nitrogen fractions · easy

A milk has 0.55 per cent total nitrogen. What is its crude protein using the milk factor?

1. 8.62 per cent
2. 3.44 per cent
3. 3.51 per cent
4. 0.09 per cent