Color of Milk
The color of milk has some importance in the dairy industry, because it is often considered an indication of its fat content.
The reflection of light on the opaque particles in suspension (casein micelles, fat globules, calcium, phosphate and citrate) produces the white color of milk.
The degree of whiteness varies with the number and size of the particles in suspension.
When fewer high wavelength are intercepted by the particles as a result of a lower concentration of large particles, the blush color of the milk becomes more apparent.
The reduction of micelle size by lowering the calcium content or by cold can also affect the whiteness of milk.
Because of their size, fat globules are very effective in reflecting long wavelengths. The homogenization of milk or cream reduces the size of the fat globules but increases their number considerably.
The bluish color of skim milk is due to a small concentration of large particles in suspension.
Milks which are abnormally rich in sodium and potassium tend to be less white, because sodium and potassium caseinates are more soluble than calcium caseinates.
This produce a decrease in the size, and sometimes the number, of casein micelles.
Milk fat contains yellow pigments which tend to mask the bluish tint of milk. The fat content in these carotenoid and xanthophylls pigment varies with type of feeding and breed.
Green forage feeds and carrots are important sources of carotene and affect the color of the milk produced by cows eating these feeds.
Color has practical applications in areas such as marketing of partially skimmed milks and coffee whiteners.
Color of Milk
