ICAR AICE-JRF/SRF Lactose, Milk Salts & Vitamins: practice questions

1 · Lactose structure, alpha and beta forms and mutarotation · medium

If the equilibrium ratio of beta to alpha lactose is 1.68, what percentage of the lactose is in the beta form?

1. 59.5 per cent
2. 37.3 per cent
3. 168 per cent
4. 62.7 per cent

2 · Lactose in sweetened condensed milk, powders and ice cream · hard

A sucrose ratio of about 62.5 to 64.5 per cent is recommended in sweetened condensed milk because:

1. Lower values cause lactose to dissolve completely and higher values prevent Maillard browning
2. Lower values allow microbial growth and higher values risk sucrose crystallisation
3. Any value above 50 per cent prevents all lactose crystallisation
4. It is the ratio at which lactose and sucrose have equal solubility

3 · Lactose in sweetened condensed milk, powders and ice cream · hard

Ice cream becomes sandy during storage mainly because:

1. Fat crystals melt and recrystallise as large beta crystals
2. Lactose crystallises in the concentrated serum, especially with high MSNF and temperature fluctuations
3. Ice crystals of more than 1 millimetre form immediately on freezing in the freezer and are felt as grains of sand
4. Sucrose reacts with milk protein to form brown granules

4 · Lactose derivatives: lactulose, galacto-oligosaccharides, lactitol, lactobionic acid · medium

Galacto-oligosaccharides are produced industrially by:

1. Transgalactosylation with beta-galactosidase at high lactose concentration
2. Fermentation of lactose to lactic acid
3. Acid hydrolysis of lactose at low concentration followed by neutralisation
4. Catalytic hydrogenation of lactose

5 · Lactose biosynthesis and intolerance · medium

According to the EFSA review, roughly how much lactose in a single dose do most people with lactose malabsorption tolerate?

1. Up to about 12 grams
2. No lactose at all
3. Up to about 100 grams
4. Up to about 0.1 gram

6 · Milk salts: calcium, phosphate, citrate and their partition · medium

Cow milk contains about 1.2 grams per litre of calcium (atomic mass 40.08). What is this in millimoles per litre?

1. About 30 millimolar
2. About 300 millimolar
3. About 48 millimolar
4. About 3 millimolar

7 · Salt balance and heat stability · hard

In processed cheese, emulsifying salts such as citrates and phosphates work by:

1. Adding calcium to para-casein so that it forms a firmer and more elastic protein network
2. Lowering the pH to the isoelectric point of casein
3. Hydrolysing fat into emulsifying monoglycerides
4. Sequestering calcium from para-casein so it hydrates and emulsifies fat

8 · Trace elements in milk · medium

Which trace element in milk is technologically important mainly as a catalyst of lipid oxidation?

1. Cobalt
2. Zinc
3. Copper
4. Selenium

9 · Trace elements in milk · medium

Selenium content of milk varies mainly with:

1. The time of day of milking
2. The selenium content of soils and feed supplements
3. The storage temperature of the milk
4. The fat content of the milk

10 · Maillard browning and its control · medium

Melanoidins in heated milk products are:

1. Red pigments formed by bacteria
2. Colourless Amadori products formed in the early stage of the reaction with lysine
3. Brown nitrogenous polymers formed in the final stage of the Maillard reaction
4. Flavour aldehydes formed by lipid oxidation