ICAR AICE-JRF/SRF Milk Lipids: practice questions

1 · Biosynthesis of milk fat · medium

From which blood fractions does the mammary gland take up preformed long-chain fatty acids?

1. Chylomicron and VLDL triglycerides, hydrolysed by lipoprotein lipase, and non-esterified fatty acids
2. Lactose and citrate transported from the liver
3. Ketone bodies converted into C18 acids in the bloodstream
4. Casein micelles and whey proteins carried in the blood plasma and taken up at the basal surface of the cell

2 · Conjugated linoleic acid · medium

Which CLA isomer inhibits milk fat synthesis and is linked with milk fat depression?

1. Cis-9, cis-11 CLA
2. Trans-10, cis-12 CLA
3. Cis-9, trans-11 CLA
4. Trans-9, trans-11 CLA

3 · Conjugated linoleic acid · hard

What is the current regulatory view of health claims for CLA?

1. They are approved for weight loss but not for other effects
2. Bodies such as EFSA have not accepted them because human evidence is insufficient
3. They are fully approved for cancer prevention in all major markets on the basis of animal studies
4. They are approved only for CLA from synthetic supplements

4 · Crystallisation and polymorphism of milk fat · medium

What is the purpose of the Alnarp cold-warm-cold cream treatment?

1. To produce softer butter from hard winter fat by controlling crystal size and liquid fat
2. To increase the beta polymorph content of butter
3. To remove cholesterol and free fatty acids from the cream before the cream is churned into butter
4. To destroy lipoprotein lipase before churning

5 · Melting behaviour and fractionation of milk fat · medium

Which fraction of milk fat is suited to butter that spreads straight from the refrigerator?

1. The high-melting fraction (stearin)
2. The unsaponifiable fraction
3. The low-melting olein
4. The membrane phospholipid fraction

6 · Auto-oxidation: mechanism, factors and measurement · medium

Which metal is the most active catalyst of lipid oxidation in milk?

1. Copper
2. Zinc
3. Magnesium
4. Calcium

7 · Antioxidants: natural and synthetic · easy

Citric acid improves the effect of phenolic antioxidants mainly by:

1. Raising the pH of the fat to inhibit oxidation
2. Donating hydrogen to lipid radicals faster than BHA
3. Chelating metal ions that catalyse initiation
4. Quenching singlet oxygen like carotene

8 · Antioxidants: natural and synthetic · easy

Which natural compound is the main chain-breaking antioxidant in milk fat?

1. Cholesterol
2. Lactose
3. Beta-carotene
4. Alpha-tocopherol

9 · Lipolysis: spontaneous and induced · medium

Which raw milk is most prone to spontaneous lipolysis?

1. Milk heated to 72 degrees Celsius immediately after milking
2. Milk from early-lactation cows on high-quality pasture
3. Milk from cows milked once a day in winter
4. Milk from late-lactation, low-yielding cows on poor feed

10 · Fat-soluble vitamins in milk, cream, butter and ghee · medium

Which processing factor causes the largest loss of vitamin A in milk and dairy fats?

1. Cold storage at 4 degrees Celsius in the dark
2. Exposure to light and oxygen during storage
3. Homogenisation at normal pressures
4. HTST pasteurisation at 72 degrees Celsius for 15 seconds