To make cheese, milk is fermented and concentrated by removal of water through the coagulation of the milk.
- Fermentation occurs through lactic acid bacteria partly from milk and mainly from the added bacteria cultures.
- Acidification by the bacteria curdles the milk.
- To help the curdling and coagulation, rennet or a similar enzyme is added.
- The separation of water is encouraged by cutting the coagulum, stirring the resulting curd, warming and pressing.
- Throughout these manufacturing steps, fermentation of lactose continues which is transformed into lactic acid.
- After pressing, the fresh cheese is immersed into a brine for salting. Alternatively, salt can be added to the curd before pressing.
- For ripened cheese, maturation follows by the action of enzymes of milk, of the rennet, of the lactic acid bacteria, and by additional cultures added. These are e.g. white mould for many soft cheeses, propionic acid bacteria for Emmental and Swiss-type cheeses or a community of bacteria and yeasts for smear-ripened cheeses such as Limburger or Gruyère.
- Thanks to the separation of water and the fermentation of lactose, cheese has a much longer shelf-life than milk. Protein, milk fat and calcium are the main constituents. Most soft, semi-hard and hard cheeses are lactose free.