Why is milk white?

Last updated 30/04/2021

Milk is a natural, whole food made up of water, protein, fat, carbohydrates in the form of lactose, vitamins including calcium, minerals including phosphorous and a range of other bioactive compounds.

Caseins are one of the main types of protein in milk which cluster together with calcium and phosphate to form tiny particles called micelles. When light hits these casein micelles it causes the light to refract and scatter resulting in milk appearing white.¹

Previously, when milk was delivered in bottles with aluminium tops, the yellow coloured fat or cream of cow’s milk would separate and rise to the top of the bottle producing a pale coloured milk. Today, most milks are homogenised which passes the milk under pressure through very fine nozzles, evenly dispersing the fat and protein micelles to create a smooth, creamy texture and taste, plus brighter white colour.

The Australian Food Standards Code allows the components of milk, such as lactose, protein, fat or vitamins and minerals to be adjusted by adding or removing those components to produce a consistent product. In earlier times natural variations in colour that would have occurred in milk because of differences between cow breeds or the pasture are now standardised and the bright, white colour consistent. There are no artificial colours added to give milk its white appearance in Australia.²