ASRB NET and ARS / SMS / STO Milk & Milk Products Technology: practice questions

1 · Milk composition · easy

Why are buffalo milk fat and buffalo ghee white while cow ghee is yellow?

1. Buffalo converts dietary beta-carotene to vitamin A, so little carotene reaches the milk fat
2. Buffalo milk fat contains more butyric acid, which bleaches the natural pigments
3. Buffalo milk has larger fat globules that scatter light and hide the carotene
4. Buffalo ghee is clarified at a higher temperature, which destroys carotene

2 · Milk composition · medium

Which component on the surface of the casein micelle keeps it stable in milk and is the target of chymosin?

1. Colloidal calcium phosphate
2. Kappa-casein
3. Beta-lactoglobulin
4. Alpha-s1-casein

3 · Adulteration of milk · medium

A seller both skims milk and adds water. Why might the lactometer reading stay normal?

1. Water and skim milk both have exactly the same specific gravity as whole milk at 15.5 degrees C
2. The lactometer measures fat only, which is restored by the added water
3. Both frauds raise the freezing point, which the lactometer compensates for
4. Skimming raises specific gravity while water lowers it, so the effects can cancel

4 · Pasteurisation · medium

A milk sample is negative for both alkaline phosphatase and lactoperoxidase. What does this show?

1. It was raw milk preserved with hydrogen peroxide
2. It was pasteurised correctly by HTST at the standard conditions of 72 degrees C for 15 seconds
3. It was heated well above pasteurisation, to about 80 degrees C or more
4. It was thermised at about 65 degrees C for 15 seconds

5 · UHT processing · medium

UHT milk made from good-tasting raw milk turns bitter and gels after four months of ambient storage, with no microbial growth. What is the usual cause?

1. Heat-stable proteases from psychrotrophic bacteria that grew in the raw milk before processing
2. Light-induced oxidation of riboflavin through the aluminium foil of the carton
3. Survival of Clostridium botulinum spores that germinated and produced toxin and gas inside the sealed package
4. Excess lactulose formed during UHT, which crystallises and thickens the milk

6 · UHT processing · medium

Skim milk powder intended for recombined milk and cheese making should be of which heat class by the whey protein nitrogen index?

1. Roller-dried powder, regardless of whey protein level
2. Low-heat powder, with most whey protein undenatured
3. Medium-heat powder forewarmed to above 120 degrees C
4. High-heat powder, with most whey protein denatured

7 · Ghee · medium

A ghee sample has a low RM value and a raised Polenske value. Which adulterant is most likely?

1. Hydrogenated cottonseed oil
2. Groundnut oil
3. Buffalo body fat
4. Coconut oil

8 · Dairy packaging · medium

Why is whole milk powder packed under nitrogen or a nitrogen-carbon dioxide mixture?

1. To prevent lactose crystallisation in the powder by excluding water vapour
2. To kill spore formers that survive spray drying
3. To make the powder more soluble when reconstituted
4. To limit fat oxidation by lowering residual oxygen in the pack

9 · Dairy quality control · easy

How many principles does HACCP comprise under the Codex General Principles of Food Hygiene?

1. Twelve
2. Ten
3. Seven
4. Five

10 · Dairy quality control · medium

In a dairy HACCP plan, the critical limit for HTST pasteurisation is 72 degrees C for 15 s. The temperature drops to 70 degrees C for 20 s. What should the corrective action include?

1. Adding 2 degrees C to the cooling section to compensate
2. Release of the milk, because the hold time of 20 s was longer than the 15 s required at the critical limit
3. Automatic diversion of the under-heated milk and holding of affected product
4. Recording the deviation only, with no action on the product