Milk is an emulsion of fats and water of animal origin that contains sugar, proteins, non-protein nitrogen substances, mineral salts, vitamins and numerous enzymes. Right from the beginning of time, mankind has consumed preferably cow and sheep’s milk, and on a lesser scale goat’s milk. The chemical composition of milk depends on the animal species. When one speaks of “milk” generally cow milk is intended.

The milk we find on sale is standardized in terms of fat contents, homogenized, pasteurized or sterilized. The thermal treatment of pasteurization brings milk to a temperature of around 72°C for at least 15 seconds.

The UHT treatment (Ultra High Temperature) is a particular sterilization technique which consists in treating homogenized milk and pre-heating it to at least 135°C using overheated water steam for no less than one second. UHT is addressed as an indirect system when the sterilization of the milk occurs through a heat exchanger, whereas direct UHT is when the sterilization of the milk occurs in direct contact with the warming fluid (the water steam). Milk is then cooled at environmental temperature and packaged under aseptic conditions. In China, the government is launching a campaign to promote milk consumption during childhood (preschool years) that could have an important impact on worldwide consumptions in the long term.