ICAR AICE-JRF/SRF 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 · Caseins: alpha-s1, alpha-s2, beta and kappa · hard

Why are caseins described as rheomorphic or intrinsically disordered proteins?

1. They fold into rigid beta-barrels that change shape only under shear
2. They are cross-linked into a fixed tertiary structure by many disulphide bonds
3. They are fully alpha-helical proteins that unfold reversibly at refrigeration temperatures and refold on warming
4. They have a high proline content and few or no disulphide bonds, so they lack a stable folded structure

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

What did the 2009 scientific review commissioned by the European Food Safety Authority conclude about beta-casomorphins?

1. A2 milk was proven to prevent heart disease and should replace A1 milk
2. A1 beta-casein was proven to cause type 1 diabetes in children
3. A cause-and-effect relationship with non-communicable diseases could not be established
4. BCM-7 was shown to be absent from the digests of all beta-casein variants, including A1 and B

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 · Heat denaturation of whey proteins and whey protein-casein interactions · hard

Beta-lactoglobulin falls from 3.2 to 0.8 grams per litre of native protein after a heat treatment. What percentage was denatured?

1. 80 per cent
2. 40 per cent
3. 25 per cent
4. 75 per cent

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