Cheese
is a food made from milk, usually the milk of cows,
buffalo, goats, or sheep, by coagulation. The milk
is acidified, typically with a bacterial culture,
then the addition of the enzyme rennet or a
substitute (e.g. acetic acid or vinegar) causes
coagulation, to give "curds and whey". Some cheeses
also have molds, either on the outer rind (similar
to a fruit peel) or throughout.
Hundreds of types of cheese are
produced. Their different styles, textures and
flavors depend on the origin of the milk (including
the animal's diet), whether it has been pasteurized,
butterfat content, the species of bacteria and mold,
and the processing including the length of aging.
Herbs, spices, or wood smoke may be used as
flavoring agents. The yellow to red color of many
cheeses is a result of adding annatto. Cheeses are
eaten both on their own and cooked in various
dishes; most cheeses melt when heated.
For a few cheeses, the milk is
curdled by adding acids such as vinegar or lemon
juice. Most cheeses are acidified to a lesser degree
by bacteria, which turn milk sugars into lactic
acid, then the addition of rennet completes the
curdling. Vegetarian alternatives to rennet are
available; most are produced by fermentation of the
fungus Mucor miehei, but others have been
extracted from various species of the Cynara
thistle family.
Cheese has served as a hedge
against famine and is a good travel food. It is
valuable for its portability, long life, and high
content of fat, protein, calcium, and phosphorus.
Cheese is more compact and has a longer shelf life
than the milk from which it is made. Cheesemakers
near a dairy region may benefit from fresher,
lower-priced milk, and lower shipping costs. The
long storage life of cheese allows selling it when
markets are more favorable.