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
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
List of cheeses typical of the United States.