Milk processing does not require any chemical treatment. Only physical processes and biochemical reactions are used.
The main treatments are as follows:
- Thermal treatments: heating milk ensures the sanitary quality of milk-based products and also has an effect on their shelf life and characteristics. Among various treatments, pasteurisation and sterilization are the most common. (See case file : Milk. Just milk.)
- Skimming: this operation consists of separating the cream from the milk in a centrifuge. The cream can then be used to produce butter or cream.
- Standardisation: Milk does not always have the same fat composition, it varies according to the seasons, cow breeds and their diet. Standardisation makes it possible to adjust the fat content of milk in order to be able to offer consumers products with constant levels of fat.
- Homogenisation: This ensures that the cream is well distributed throughout the milk. It is a physical process that reduces the size of fat globules to fine droplets, which prevents the cream from rising to the surface of the milk.
- Fermentation: This essential step in the production of cheeses, yoghurts and fermented milks transforms liquid milk into a thickened and acidified product. For yoghurt, ferments (Lactobacillus bulgaricus, Streptococcus thermophilus) develop aromas and provide texture. Each manufacturer has developed its own recipe.
- Curdling: This step is essential in the production of cheese. As it curdles, the milk passes from a liquid state to a semi-solid state. Curdling occurs through the action of coagulants, for example rennet and/or acidifying bacteria.
- Draining: This consists in the elimination of whey in order to concentrate the caseins, the major constituents of most cheeses.
- Salting: On completing the draining of the cheese, salting helps the formation of the rind, thus helping to preserve it. Cheese can be salted in two ways: dry, by sprinkling it with salt or by immersing it in a brine bath.
- Maturing: The object is to transform the unripened cheese into a tasty paste. The quality of the maturing process depends on the management of time, temperature and humidity in the cellars as well as on the presence of micro-organisms. These parameters vary according to the category of cheese.
- Ultrafiltration: This process consists in filtering the milk through a membrane under pressure, in order to recover certain components such as whey proteins and caseins. This is called splitting. These ingredients can be used in the manufacture of many food products (such as soups, sauces and ready meals), non-food products (such as glue, biomaterials, and coatings) or pharmaceutical products. Ultrafiltration is also used to pre-concentrate milk for the production of certain cheeses.
- Microfiltration is also a technique of separation under pressure. It is used to eliminate bacteria from milk.
- Drying: Milk is made up of 90% water. It is dehydrated to transform it into powder, thus making it easier to preserve, store and transport.