ICAR AIEEA-PG Milk Lipids: practice questions

1 · Lipid classes in milk: triglycerides, phospholipids, sterols · easy

Which three phospholipids are the main ones in cow milk?

1. Cerebroside, ganglioside and phosphatidylglycerol
2. Phosphatidylserine, phosphatidylinositol and cardiolipin
3. Phosphatidylcholine, phosphatidylethanolamine and sphingomyelin
4. Lysophosphatidylcholine, ethanolamine plasmalogen and phosphatidic acid

2 · 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

3 · Conjugated linoleic acid · easy

Which isomer makes up most of the conjugated linoleic acid in milk fat?

1. Trans-10, cis-12 C18:2
2. Trans-11 C18:1 (vaccenic acid)
3. Cis-9, cis-12 C18:2 (linoleic acid)
4. Cis-9, trans-11 C18:2 (rumenic acid)

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 · 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

7 · 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

8 · Antioxidants: natural and synthetic · hard

Why does ghee prepared at a higher clarification temperature usually keep better?

1. Higher temperature adds iron from the pan, which stabilises the fat against oxidation in storage
2. More phospholipids pass into the fat and Maillard products with antioxidant activity form
3. Higher temperature converts cholesterol into tocopherol
4. Higher temperature removes all unsaturated fatty acids from the fat

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