Skimmed milk

Skimmed milk, or skim milk, is made when all the milkfat is removed from whole milk. It tends to contain around 0.1% to 0.3% fat.

Background

Historically, skimmed milk was used for fattening pigs, and was recommended as "not only the very best supplement for growing pigs, but is of almost equal value for fattening purposes" as it "furnishes a complete protein" and makes the feed "more palatable".

Terminology

In the United Kingdom, milk has been traditionally marketed and labelled as follows since being proposed by John Morris of the British Retail Consortium in 1998, which based the colours on Marks & Spencer cream packaging :

Whole milk – Plastic bottles marketed in blue packaging.
Semi-skimmed milk – Plastic bottles are marketed in green packaging.
Skimmed milk – Plastic bottles are marketed in red packaging.
Channel Island milk Often referred to as gold top, although this varies.

Additionally, some supermarkets in the UK now market milk as:

1% fat milk – Normally sold in purple or orange packaging.

In the UK, milk is sometimes still delivered on the doorsteps by a milkman in the early hours of the morning in glass pint bottles with the colour printed foil lid indicating the milkfat content. Whole milk had plain silver foil, semi-skimmed milk had silver foil with red stripes and skimmed milk silver foil with a blue checker pattern.
In the United States, milk is marketed primarily by fat content and available in these varieties:

Whole milk is 3.5% fat
2% Reduced-fat milk
1% Lowfat milk
0% Non-fat milk

United States milk producers also use a color-coding system to identify milk types, usually with the bottle cap or colored accents on the packaging. Whole milk is often denoted by red, while 2% is most often colored blue. 1% and skim colors vary by region or dairy, with common colors for these lines being purple, green, yellow, pink, or light blue.

Production

Most skimmed milk is created by spinning whole milk in a centrifuge so that the fat droplets separate out.