ICAR AICE-JRF/SRF Advanced Dairy Chemistry: practice questions

1 · Chemical and enzyme kinetics in milk systems · hard

Using z ≈ 2.303RT²/Eₐ, estimate z at 120 °C (393 K) for a browning reaction with Eₐ = 100 kJ/mol.

1. 3.0 K
2. 30 K
3. 13 K
4. 68 K

2 · Chemical and enzyme kinetics in milk systems · hard

Moderately heated milk can show higher plasmin activity in storage than raw milk because heat:

1. Heat converts β-casein directly into plasminogen in the micelle
2. Activates lipoprotein lipase, which cleaves casein
3. Heat destroys the inhibitors first
4. Removes all plasminogen from the micelles

3 · Protein-protein interactions under heat and pressure · medium

Under high hydrostatic pressure, which whey protein is the most resistant?

1. β-Lactoglobulin
2. α-Lactalbumin
3. Bovine serum albumin
4. Immunoglobulin G

4 · Protein-protein interactions under heat and pressure · hard

Alkaline phosphatase cannot be used to verify high-pressure processing of milk because it:

1. It is destroyed by any pressure above 10 MPa within seconds
2. Is absent from raw milk
3. Is produced by pressure-treated bacteria
4. It survives commercial pressures

5 · Maillard reaction pathways and advanced glycation products · medium

Furosine in milk is formed:

1. Naturally in the udder of every cow before milking
2. From lipid oxidation of fatty acids
3. From lactose by isomerisation
4. From Amadori products in acid hydrolysis

6 · Maillard reaction pathways and advanced glycation products · medium

Strecker degradation converts an amino acid into an aldehyde with:

1. Two more carbons
2. The same number of carbons and no CO₂
3. One carbon fewer, plus CO₂
4. A sugar attached

7 · Mineral equilibria modelling · hard

Mineral equilibrium calculations must be iterative mainly because:

1. Equilibrium constants change with every repeated measurement
2. Milk composition is unknown
3. Ions are not conserved
4. Ionic strength depends on the speciation being solved

8 · Proteomics, lipidomics and metabolomics of milk · medium

In bottom-up proteomics of milk, proteins are usually:

1. Analysed intact by Kjeldahl nitrogen and the 6.38 factor
2. Trypsin-digested and analysed by LC-MS/MS
3. Identified by Gerber tests
4. Separated only by isoelectric precipitation at pH 4.6

9 · Proteomics, lipidomics and metabolomics of milk · hard

A metabolomics study with 30 samples and 2,000 variables reports perfect separation of two groups by PLS-DA. The main concern is:

1. Too few variables measured for a multivariate model
2. NMR cannot be used for milk
3. Overfitting
4. PLS-DA cannot classify samples

10 · Bioactive components and their analysis · medium

Lactoferrin's main antimicrobial mechanism is:

1. Withholding iron
2. Hydrolysing peptidoglycan in Gram-positive cell walls
3. Producing hypothiocyanite
4. Coagulating casein