Question

What is the average per cent of cholesterol in total lipids fraction of milk?

• A. 0.46%
• B. 2.0%
• C. 0.1%
• D. 3.0%

Hint:

Milk Lipid Fractions:
Triglycerides = $98\%$.
Phospholipids = $0.8\%$.
Cholesterol = 0.30%--0.46% of total fat ($10 - 15\text{ mg/100 mL}$).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Bovine milk unsaponifiable sterol lipid fraction: cholesterol constitutes approximately 0.30% to 0.46% of total milk lipids (10--15 mg/100g whole milk), existing primarily as free unesterified sterol in the milk fat globule membrane.
Key Formula or Approach:
\[ \text{Cholesterol in Milk Fat} \approx 0.30\% - 0.46\% \text{ of Total Lipids} \quad (10 - 15\text{ mg Cholesterol / 100 g Whole Milk}) \]

Step 2: Detailed Explanation:
In milk lipid composition and sterol chemistry:
- Bovine milk lipid is composed of:
1. Triglycerides (Triacylglycerols): $97.5\% - 98.0\%$ of total lipids.
2. Diglycerides & Monoglycerides: $0.5\% - 1.0\%$.
3. Phospholipids: $0.5\% - 1.0\%$.
4. Sterols (dominated by Cholesterol) (A): Total sterols constitute the major unsaponifiable lipid fraction. Cholesterol represents 0.30% to 0.46% (average 0.46%) of the total lipid fraction in bovine milk (with $\approx 85\% - 90\%$ present as free unesterified cholesterol and $10 - 15\%$ as cholesteryl esters, localized predominantly in the outer milk fat globule membrane [MFGM]).

Step 3: Final Answer:
Therefore, the average per cent of cholesterol is 0.46%, corresponding to option (A).