ASRB NET and ARS Milk Composition & Physical Properties: practice questions

1 · Gross composition of milk and its normal ranges · easy

Which major constituent of cow milk varies least between individual cows and herds?

1. Lactose, because it sets most of the osmotic pressure of milk
2. Ash, because mineral intake does not change from day to day
3. Casein, because its synthesis is fixed by the animal's breed
4. Fat, because it is synthesised directly from blood glucose

2 · Gross composition of milk and its normal ranges · medium

What is the typical size range of casein micelles in cow milk?

1. About 3 to 6 nanometres, roughly the size of single whey protein molecules
2. About 50 to 500 nanometres, averaging near 150 to 200 nanometres
3. About 0.1 to 15 micrometres, averaging near 3 to 4 micrometres
4. About 20 to 50 micrometres, visible under a hand lens

3 · Species differences: cow, buffalo, goat, sheep, camel, human · medium

Which protein is absent from both human and camel milk but is the main whey protein of cow milk?

1. Alpha-lactalbumin
2. Lactoferrin
3. Serum albumin
4. Beta-lactoglobulin

4 · Variation with breed, feed, season, lactation stage and mastitis · easy

Compared with fore-milk, the strippings at the end of milking are:

1. Similar in every constituent
2. Much richer in lactose
3. Much richer in fat
4. Much lower in fat and protein

5 · Colostrum and abnormal milks · easy

Which constituent is present at a much lower concentration in first-milking colostrum than in normal milk?

1. Total protein
2. Vitamin A
3. Immunoglobulin
4. Lactose

6 · Density and specific gravity; lactometer readings · medium

Using Richmond's formula for readings at 60 degrees Fahrenheit, what is the SNF of milk with 3.5 per cent fat and a corrected lactometer reading of 26.6?

1. 7.53 per cent
2. 7.39 per cent
3. 11.03 per cent
4. 6.79 per cent

7 · Buffer capacity and acid-base equilibria · medium

Which statement about the buffering of buffalo milk compared with cow milk is correct?

1. Both are equally buffered, because buffering depends only on lactose
2. Buffalo milk is weakly buffered because it lacks citrate
3. Buffalo milk is weakly buffered because its larger fat globules dilute the proteins
4. Buffalo milk is more strongly buffered because it has more casein and phosphate

8 · Viscosity, surface tension and interfacial tension · easy

Which milk component contributes most to the viscosity of whole milk?

1. Soluble salts
2. Whey proteins
3. Casein micelles
4. Lactose

9 · Electrical conductivity, refractive index and thermal properties · easy

The refractive index of milk at 20 degrees Celsius is about:

1. 1.344 to 1.348
2. 1.333
3. 1.500 to 1.520
4. 1.454 to 1.462

10 · Electrical conductivity, refractive index and thermal properties · easy

The specific heat of whole milk is about:

1. 1.0 kilojoule per kilogram per kelvin
2. 3.9 kilojoules per kilogram per kelvin
3. 2.1 kilojoules per kilogram per kelvin
4. 4.18 kilojoules per kilogram per kelvin