Why Is Milk White? | Notes And Queries | .uk

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Adam Powell, Swansea, UK

• Not all milk is. Flamingoes (one of only two types of bird to produce it) have bight red milk.

  Seth, Edinburgh, Scotland

• Milk is white because it does not have a constant refractive index throughout and this makes the light scatter and reflect. It is basically fat and protein suspended in water. Cream has a higher fat content, and carotene in fat globules scatters yellow light and is responsible fot the different color of cream.

  Philip Clarke, Letchworth UK

• Milk is white because it is made up predominantly of white blood cells (or puss if you prefer). So when you have a glass of milk you are in fact drinking a glass of puss. Yuck!

  Michael Wakefield, East London South Africa

• Milk is made up of a "water phase" and a "fat phase". The water phase contains minerals and vitamins etc in a simple solution which is colourless and transparent. However, milk is made white and opaque by the "colloid suspension" which consists of very small particles of casein proteins. As these are in suspension and not dissolved, they make milk white and opaque.

  Sophie Bailey, Shropshire, UK

• Milk may contain a very few cells, but Michael Wakefield is (fortunately) wrong that it is mainly cells. Milk or cream is droplets of yellowish butter-fat and protein suspended in a slightly yellow or greenish watery liquid. The white is like the white of snow or salt, due to the scattering of light by millions of fat droplets. Butter is the reverse -- droplets of watery liquid suspended in continuous butterfat. Clarified butter is the butterfat with the watery part dried out by heating, so making it clear.

  Richard Collingridge, Ringwood UK