Milk is an emulsion of butterfat globules within a water-based fluid. Each fat globule is surrounded by a membrane consisting of phospholipids and proteins. Ordinary fresh milk sold for domestic use must contain a minimum of 3,3%fat and 8,5% fat-free solids. Most milk that is consumed via commercial sources today is processed in at least one of the following ways:
Milk is exposed to intensified temperature, usually 72°C, for fifteen seconds. This destroys all the pathogenic organisms, the heat resistant tuberculosis bacteria, as well as approximately 90 percent of all remaining organisms, without causing any visible changes.
Most liquid milk products are homogenised. This involves the breaking down of milk fats into small particles so that a layer of cream is not formed on the surface.
This is the deliberate modification of milk composition by removing milk fats to reduce the fat content to the required 3.3%, or to control the total solids composition of milk products.
Source: Parmalat
The different milks tend to vary according to the way they are produced, and their fat content. The fat content of milk varies depending on the product e.g. whole milk has a fat content of about 4% fat, whole standardised milk, that which is widely available for sale, has a minimum fat content of 3.3% fat, semi skimmed milk contains 1.7% fat, skimmed milk contains about 0.2% fat, and in addition there is 1% fat milk.
Full cream milk
Natural whole milk is milk with nothing added or removed. Whole standardised milk is whole milk standardised to a minimum fat content of 3.3%. Whole homogenised milk is identical in fat and nutrient content to whole standardised milk however it has undergone a specific process known as “homogenisation” which breaks up the fat globules in the milk. This spreads the fat evenly throughout the milk and prevents a creamy layer forming at the top. Much of the milk in the market is now homogenised as well as pasteurised. Homogenisation offers a way to reduce the fatty sensation of whole milk and prevent the formation of a cream plug.
Low Fat Milk
Semi skimmed milk is the most popular type of milk in the UK with a fat content of 1.7%, compared to a minimum of 3.3% in full cream milk and 0.2% in skimmed milk.
Fat Free Milk
Skimmed milk has a fat content of between 0-0.5% and an average fat content of 0.1%. Skimmed milk therefore has nearly all the fat removed. It contains slightly more calcium than whole milk and lower levels of fat soluble vitamins, particularly vitamin A, as this is lost when the fat is removed-see nutritional composition of milks
The lower level of fat in skimmed milk reduces its calorie (energy) content. For this reason it is not recommended for children under the age of 5 years as they need the extra energy for growth. However it is ideal for adults who wish to limit their fat or calorie intake. Skimmed milk has a slightly more watery appearance than other types of milk and has a less creamy taste due to the removal of fat.
Source: Dairy Council (United Kingdom)