Cheese consists mainly of casein (the principal protein in milk), fat and a certain proportion of water which is incorporated or fixed in the cheese. Worldwide there are over 2,000 different types of cheese, some of which exhibit widely differing properties.

These can be roughly divided into three main groups:

The milk is mixed with rennet (enzymes extracted with the aid of micro-organisms). The action of these enzymes causes the casein to lose its original chemical structure. It ceases to be soluble and coagulates. The liquid which remains is whey which must be separated from the coagulated casein, known as curds. The curds are then put into a mould, pressed, and salted. Fungal and bacterial cultures and spices are added as necessary. Depending on type, the cheese is then either eaten fresh or left to mature, a process which for some cheeses can last many months.