ICAR AIEEA-PG Chemistry of Dairy Products: practice questions

1 · Heat stability of milk and the heat coagulation time · medium

Above about pH 6.7, heating milk causes which change in kappa-casein that contributes to instability?

1. Cleavage at Phe105-Met106 by heat alone without enzyme
2. Conversion into alpha-s1-casein by isomerisation
3. Dissociation from the micelles
4. Crystallisation as calcium kappa-caseinate on the tube wall

2 · Age gelation of UHT milk · medium

Which enzymes are chiefly responsible for proteolytic age gelation of UHT milk?

1. Lipoprotein lipase and xanthine oxidoreductase
2. Plasmin and heat-stable proteases of psychrotrophic bacteria
3. Chymosin and pepsin carried over from cheese plants sharing the same raw milk
4. Alkaline phosphatase and lactoperoxidase

3 · Chemistry of cream: neutralisation and ripening · easy

Why is sour cream partly neutralised before pasteurisation for butter or ghee?

1. To remove carotene and make the butter whiter
2. To prevent curdling on heating and reduce fat loss
3. To raise the lactose content so the cream churns faster
4. To increase the iodine value of the fat

4 · Ghee: composition by method, analytical constants, flavour and deterioration · easy

In the pre-stratification method of ghee making, butter is first held at about:

1. 40 degrees Celsius
2. 120 degrees Celsius
3. 4 degrees Celsius
4. 80 degrees Celsius

5 · Ghee: composition by method, analytical constants, flavour and deterioration · medium

What gives traditional ghee its granular texture?

1. Slow cooling
2. Rapid chilling to below 0 degrees Celsius
3. Addition of sugar during clarification
4. Residual casein forming lumps in the fat

6 · Chemistry of rennet coagulation · medium

Using Van Slyke's formula Y = (0.93F + C - 0.1) x 1.09 / (1 - W), what is the yield of Cheddar from 100 kilograms of milk with 3.6 per cent fat, 2.5 per cent casein and 37 per cent cheese moisture?

1. About 9.9 kilograms
2. About 9.1 kilograms
3. About 6.3 kilograms
4. About 15.8 kilograms

7 · Chemistry of rennet coagulation · medium

What does a high C/P ratio of a coagulant mean?

1. High coagulation pH relative to ripening pH
2. High casein content relative to protein
3. High clotting activity relative to general proteolysis
4. High calcium relative to phosphate

8 · Chemistry of rennet coagulation · easy

Which coagulant is now the most widely used in cheesemaking?

1. Papain
2. Calf rennet extracted from abomasa
3. Pig pepsin from slaughterhouses
4. Fermentation-produced chymosin

9 · Chemistry of rennet coagulation · medium

Which coagulant is noted for very specific kappa-casein cleavage with little general proteolysis?

1. Rhizomucor miehei protease
2. Cryphonectria parasitica protease
3. Camel chymosin
4. Bovine pepsin

10 · Changes during cheese ripening: glycolysis, proteolysis, lipolysis · medium

Which agent in Dutch-type cheeses produces the small round openings?

1. Clostridia producing hydrogen
2. Moulds producing ammonia
3. Citrate-fermenting lactococci and leuconostocs producing CO2
4. Propionibacteria producing CO2 from lactate in the warm ripening room