Cheese is a food derived from milk that is produced in a wide range of flavours, textures, and forms by coagulation of the milk protein casein. It comprises proteins and fat from milk, usually the milk of cows, buffalo, goats, or sheep. During production, the milk is usually acidified, and adding the enzyme rennet causes coagulation. The solids are separated and pressed into final form. Some cheeses have melds on the rind, the outer layer, or throughout. Most cheeses melt at cooking temperature.
Hundreds of types of cheese from various countries are produced. Their styles, textures and flavours depend on the origin of the milk (including the animal's diet), whether they have been pasteurized, the butterfat content, the bacteria and meld, the processing, and aging. Herbs, spices, or wood smoke may be used as flavouring agents. The yellow to red colour of many cheeses, such as Red Leicester, is produced by adding annatto. Other ingredients may be added to some cheeses, such as black pepper, garlic, chives or cranberries.
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. Cheesemakers near a dairy region may benefit from fresher, lower-priced milk, and lower shipping costs.
Cheese is valued 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 milk, although how long a cheese will keep depends on the type of cheese; labels on packets of cheese often claim that a cheese should be consumed within three to five days of opening. Hard cheeses, such as parmesan last longer than soft cheeses, such as Brie or goat's milk cheese. The long storage life of some cheeses, especially when encased in a protective rind, allows selling when markets are favourable.
There is some debate as to the best way to store cheese, but some expertsmsay that wrapping it in cheese paper provides optimal results. Cheese paper is coated in a porous plastic on the inside, and the outside has a layer of wax. This specific combination of plastic on the inside and wax on the outside protects the cheese by allowing condensation on the cheese to be wicked away while preventing moisture from within the cheese escaping.
A specialist seller of cheese is sometimes known as a cheesemonger. Becoming an expert in this field requires some formal education and years of tasting and hands-on experience, much like becoming an expert in wine or cuisine. The cheesemonger is responsible for all aspects of the cheese inventory: selecting the cheese menu, purchasing, receiving, storage, and ripening.
Preserved cheese was found in the Taklamakan Desert in Xinjiang, China in 1615 BC. The earliest evidence of cheese (GA.UAR) is the Sumerian cuneiform texts of Third Dynasty of Ur, dated at the early second millennium BC. Visual evidence of Egyptian cheesemaking was found in Egyptian tomb murals in approximately 2000 BC. The earliest cheeses were sour and salty and similar in texture to rustic cottage cheese or present-day feta. In Late Bronze Age Minoan-Mycenaean Crete, Linear B tablets recorded the inventorying of cheese, flocks and shepherds. An Arab legend attributes the discovery of cheese to an Arab trader who used this method of storing milk. However, cheese was already well-known among the Sumerians.
Shards of pottery pierced with holes found in pile-dwellings are hypothesized to be cheese-strainers. They are of the Urnfield culture on Lake Neuchatel and date back to 6,000 BC. The earliest evidence of cheese-making dates back to 5,500 BC in Kujawy, Poland. For preservation purposes, cheese-making may have begun by the pressing and salting of curdled milk. Curdling milk in an animal's stomach made solid and better-textured curds, leading to the addition of rennet. Dairying existed around 4,000 BC in the grasslands of the Sahara. Hard salted cheese is likely to have accompanied dairying from the outset. It is the only form in which milk can be kept in a hot climate. Animal skins and inflated internal organs provided storage vessels for a range of foodstuffs. Cheese produced in Europe, where climates are cooler than in the Middle East, required less salt for preservation. With less salt and acidity, the cheese became a suitable environment for useful microbes and molds, giving aged cheeses their pronounced and interesting flavors.