Question

The Yellow colour of cow milk compared to the White colour of buffalo milk is due to ______.

• A. Riboflavin
• B. Beta-carotene
• C. Bilirubin
• D. Casein concentration

Hint:

Cows pass dietary beta-carotene directly into their milk fat, giving cow ghee and milk a yellow tint. Buffaloes convert all beta-carotene into colorless Vitamin A, so buffalo milk and ghee remain pure white.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the specific lipid-soluble pigment responsible for the distinct pale-yellow tint of cow milk compared to the brilliant white color of buffalo milk.

Step 2: Detailed Explanation:

• Pigments in Milk: Milk contains several pigments, but its primary color is determined by the scattering of light by suspended casein micelles and emulsified fat globules, combined with dissolved fat-soluble pigments.

• Beta-carotene Transfer:

• Cows consume beta-carotene ($\beta$-carotene) from green forage. Cows lack the metabolic pathway to fully convert all ingested beta-carotene into Vitamin A in their intestines.

• As a result, excess beta-carotene is absorbed into the bloodstream and transferred directly into the fat phase of cow milk. This lipid-soluble carotenoid imparts a characteristic pale-yellow tint.

• Buffalo Metabolism: In contrast, buffaloes possess an efficient enzyme system in their intestinal mucosa that completely converts all ingested beta-carotene into colorless Vitamin A (retinol). Therefore, no carotenoid pigment enters the milk fat phase, resulting in buffalo milk fat being colorless and the milk appearing bright white.

• Other Options: Riboflavin (vitamin $B_2$) is a water-soluble pigment that imparts a greenish-yellow tint to liquid whey (seen after curd coagulation), not the yellow tint of whole milk fat. Bilirubin is a bile pigment not normally present in milk. Casein concentration affects the opacity and whiteness of the milk.

Step 3: Final Answer:
The yellow color of cow milk is due to the presence of beta-carotene in its fat phase, corresponding to option (B).