ICAR AIEEA-PG Dairy Analysis & Instrumental Methods: practice questions

1 · 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

2 · Aflatoxin M1 detection · medium

The European Union limit for aflatoxin M1 in milk is:

1. 50 micrograms per kilogram
2. 0.5 micrograms per kilogram
3. 0.050 micrograms per kilogram
4. 5 micrograms per kilogram

3 · 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

4 · 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

5 · 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

6 · Chromatography: TLC, GC and HPLC · easy

The most common HPLC column type in food analysis is:

1. Ion-exchange for sugars only
2. Packed GC column
3. Reversed-phase C18
4. Size-exclusion only

7 · 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

8 · 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

9 · 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

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

What is a certified reference material?

1. A sample sent by a customer for analysis
2. A material with certified values, uncertainty and traceability
3. Any sample analysed twice in the same laboratory on different days
4. A reagent of analytical grade purity