ICAR AICE-JRF/SRF Dairy Analysis & Instrumental Methods: practice questions

1 · Platform tests: organoleptic, COB, alcohol, sediment, lactometer · hard

Milk from a herd with high mastitis passes the clot-on-boiling test but flocculates in the alcohol test. Why?

1. The COB test is more sensitive to acidity than the alcohol test at every level
2. Alcohol stability falls with abnormal milk before COB fails
3. Mastitic milk contains alcohol-producing yeasts
4. Boiling removes mastitis bacteria, so the COB test cannot detect them

2 · Detection of adulterants: water, starch, urea, neutralisers, detergent, vegetable fat · hard

Why are quantitative methods and limits needed to prove addition of urea to milk?

1. Urea evaporates during testing
2. Milk contains urea naturally, so its presence alone proves nothing
3. Urea is identical to lactose in all chemical tests, so it cannot be told apart from it
4. Urea is detected only by the Gerber test

3 · Detection of adulterants: water, starch, urea, neutralisers, detergent, vegetable fat · hard

Which method can detect cow milk added to buffalo milk?

1. An immunological test with antiserum against cow milk proteins
2. The Gerber fat test
3. The clot-on-boiling test, since cow milk clots sooner than buffalo milk
4. The lactometer test

4 · Ghee and butter fat adulteration: BR reading, Reichert-Meissl and Polenske values, sterol tests · hard

Why do animal body fats such as tallow escape detection by the phytosterol acetate test?

1. They dissolve the sterol acetates completely
2. They have a much higher Reichert-Meissl value than genuine ghee
3. They contain more phytosterols than vegetable oils
4. They contain cholesterol, not phytosterols, like milk fat

5 · Spectroscopy: UV-visible, infrared, atomic absorption and flame photometry · medium

A calibration line has slope 0.05 absorbance units per milligram per litre and intercept 0.01. A sample reads 0.36. What is its concentration?

1. 7.0 milligrams per litre
2. 0.018 milligrams per litre
3. 7.2 milligrams per litre
4. 18 milligrams per litre

6 · Spectroscopy: UV-visible, infrared, atomic absorption and flame photometry · hard

Why is lanthanum added when calcium in milk is determined by flame atomic absorption?

1. To dissolve the fat
2. To overcome phosphate interference that lowers the calcium signal
3. To raise the flame temperature
4. To provide the characteristic light source needed for calcium in the flame

7 · Spectroscopy: UV-visible, infrared, atomic absorption and flame photometry · easy

Flame photometry is used mainly to determine:

1. Fat and protein
2. Lactose and sucrose
3. Sodium and potassium
4. Lead and cadmium

8 · Electrophoresis and immunoassays: SDS-PAGE, ELISA and lateral-flow tests · medium

The EU reference method for cow milk in sheep, goat or buffalo cheese uses:

1. The Reichert-Meissl value of the fat extracted from the cheese
2. Gerber fat analysis
3. Isoelectric focusing of gamma-caseins after plasmin digestion
4. SDS-PAGE of whey proteins

9 · Method validation, reference materials and proficiency testing · hard

With a standard deviation of 0.004 and a calibration slope of 0.08 per unit, what is the limit of detection using 3.3 s/slope?

1. About 3.3 units
2. About 0.5 unit
3. About 0.013 unit
4. About 0.17 unit

10 · Method validation, reference materials and proficiency testing · medium

Repeatability refers to precision measured under which conditions?

1. Same analyst, equipment and laboratory over a short time
2. Different samples from the same batch
3. Different methods on the same sample
4. Different laboratories with different analysts