Milk is a fresh and natural product that comes directly from a living animal: the cow. This raw cow milk naturally contains bacteria. Ambient bacteria can greatly shorten the milk’s shelf life. So it is important to give these organisms as little opportunity as possible to get into and grow in the milk. This goes for the entire milk production process, from cow to consumer.
It all starts with the dairy farmer who must ensure good hygiene in the cow’s living environment, with clean lying areas and walking paths in the stable. A hygienic milking method is vital for the milk’s shelf life.
Milk is warm in the cow’s udder – as warm as the cow’s body temperature. Immediately after milking the milk is chilled on the farm to preserve its quality and inhibit bacteria growth.
After the milk trucks have collected the chilled milk, it is processed at the dairy plant. There are various ways to extend the shelf life of milk. One is by heating. Heating removes harmful bacteria from the milk. The higher the temperature, the more bacteria are eliminated. The principal heating methods used in western countries are: pasteurisation, sterilisation and UHT (ultra-high temperature).
Milk powder and condensed milk
There are two other ways to extend milk’s shelf life. Extracting all water from milk results in milk powder. Milk powder can be kept for years, even outside the fridge. Concentrated or condensed milk also keeps for a very long time outside the fridge due to the addition of sugar.
Whereas heating removes harmful bacteria, fermentation of milk involves the addition of ‘good’ bacteria. This often changes the flavour and texture of milk and extends its shelf life. Milk fermentation forms the basis of butter, cheese and yoghurt.
Hygiene in the dairy plant
All employees and processes in dairy plants must conform to strict hygiene regulations. This is vital to ensure that bacteria get as little chance as possible during the production processes in the plant.
Many dairy plants work with quality systems that specify exactly how processes must be conducted, when cleaning must take place, how temperature control is carried out and what hygiene measures employees must apply in the dairy plants. These quality systems are often subject to regular checks by external organisations.
In the consumer’s home
Good consumer habits can also extend the shelf life of milk products. It is important to ensure that the temperature of dairy produce does not rise too much on the way from the shop to the consumer’s home. Consumers must place their milk products in a sufficiently cool fridge as soon as possible. Domestic hygiene is also crucial.