Pigment Responsible for Colour of Whey and Skim Milk

Greenish-yellow colour of whey and bluish colour of skim milk is due to:

Correct Answer: Riboflavin

Riboflavin (Vitamin B2) is a water-soluble, greenish-yellow fluorescent pigment. It remains in the aqueous (whey/serum) fraction of milk and is responsible for the greenish-yellow colour of whey. In skim milk (where fat and carotene are removed), the riboflavin gives a bluish tint.

Colour-Causing Pigments in Milk and Dairy Products

• Riboflavin: Greenish-yellow colour of whey; bluish colour of skim milk.
• β-Carotene: Yellow colour of cow milk and cow butter (carotene from green feed/grass).
• Casein protein: White colour of buffalo milk (buffaloes convert all carotene to Vitamin A, so no carotene in their milk).
• Annatto: Colouring agent added to butter to give it a yellow colour; also used as a food colour in cheese.

Stall-fed vs. Grass-fed Cattle Milk Colour

• Stall-fed cow: White-yellowish milk (less carotene in feed).
• Grass-fed cow: Yellow colour milk (more carotene from green pasture).