Under any name, cheese is a beloved food around the world, and it has been for a long time. Cheese is made of proteins and fats from milk, often matured by bacteria or other organisms. No one knows how it was invented, but one legend has it that a herdsman stored milk in a bag made from an animal's stomach. The heat of the day, aided by bacteria and enzymes in the stomach lining, made the milk curdle and ripen, producing cheese. True or not, this story highlights the basics of cheese production.
Milk is heated, which separates proteins from the surrounding water.
The process works best if there's acid in the milk. Cheese makers either let the milk go sour naturally or add bacterial starter cultures to sour it more quickly. The remaining liquid, called whey, is poured off. Then most cheeses are ripened, a process in which enzymes from bacteria, fungi or yeasts change the structure of the proteins and fats in the cheese, altering its flavor, color and texture. The kind of cheese you end up with depends on many factors, including the microorganisms used, the temperature and how the cheese is handled during ripening.