Curdled milk food product
Cheese is a type of dairy product produced in a range of flavors, 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, milk is usually acidified and either the enzymes of rennet or bacterial enzymes with similar activity are added to cause the casein to coagulate. The solid curds are then separated from the liquid whey and pressed into finished cheese. Some cheeses have aromatic molds on the rind, the outer layer, or throughout.
Over a thousand types of cheese exist, produced in various countries. Their styles, textures and flavors depend on the origin of the milk (including the animal's diet), whether they have been pasteurised, the butterfat content, the bacteria and mold, the processing, and how long they have been aged. Herbs, spices, or wood smoke may be used as flavoring agents. Other added ingredients may include black pepper, garlic, chives or cranberries. A cheesemonger, or specialist seller of cheeses, may have expertise with selecting, purchasing, receiving, storing and ripening cheeses.
Most cheeses are acidified by bacteria, which turn milk sugars into lactic acid; the addition of rennet completes the curdling. Vegetarian varieties of rennet are available; most are produced through fermentation by the fungus "Mucor miehei", but others have been extracted from "Cynara" thistles. For a few cheeses, the milk is curdled by adding acids such as vinegar or lemon juice. 
Cheese is valued for its portability, long shelf life, and high content of fat, protein, calcium, and phosphorus. Cheese is more compact and has a longer shelf life than milk. 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 favorable. Vacuum packaging of block-shaped cheeses and gas-flushing of plastic bags with mixtures of carbon dioxide and nitrogen are used for storage and mass distribution of cheeses in the 21st century, compared the paper and twine that was used in the 20th and 19th century.
Etymology.
The word "cheese" comes from Latin ', from which the modern word casein is derived. The earliest source is from the proto-Indo-European root "*kwat-", which means "to ferment, become sour". That gave rise to ' or ' (in Old English) and ' (in Middle English). Similar words are shared by other West Germanic languages—West Frisian ', Dutch ', German ', Old High German '—all from the reconstructed West-Germanic form "*kāsī", which in turn is an early borrowing from Latin.
The "Online Etymological Dictionary" states that "cheese" derives from:
 ;templatestyles src="Template:Blockquote/styles.css" / ;Old English (West Saxon), (Anglian) ... from West Germanic *kasjus (source also of Old Saxon "kasi", Old High German ', German ', Middle Dutch ', Dutch '), from Latin ' [for] "cheese" (source of Italian ', Spanish ', Irish ', Welsh "").
The "Online Etymological Dictionary" states that the word is of:
 ;templatestyles src="Template:Blockquote/styles.css" / ;unknown origin; perhaps from a PIE root *kwat- "to ferment, become sour" (source also of Prakrit "buttermilk;" Old Church Slavonic "leaven; fermented drink," "sour," - "to turn sour;" Czech "to turn sour, rot;" Sanskrit kvathati "boils, seethes;" Gothic hwaþjan "foam").
When the Romans began to make hard cheeses for their legionaries' supplies, a new word started to be used: ', from ', or "cheese shaped in a mold". It is from this word that the French ', standard Italian ', Catalan ', Breton ', and Occitan ' (or ') are derived. Of the Romance languages, Spanish, Portuguese, Romanian, Tuscan and some Southern Italian dialects use words derived from ' (', ', ', and "" for example). The word "cheese" is occasionally employed, as in "Head cheese", to mean "shaped in a mold".
History.
Origins.
Cheese is an ancient food whose origins predate recorded history. There is no conclusive evidence indicating where cheesemaking originated, whether in Europe, Central Asia or the Middle East. The earliest proposed dates for the origin of cheesemaking range from around 8000 BCE, when sheep were first domesticated. Because animal skins and inflated internal organs have provided storage vessels for a range of foodstuffs since ancient times, it is probable that the process of cheese making was discovered accidentally by storing milk in a container made from the stomach of an animal, resulting in the milk being turned to curd and whey by the rennet from the stomach. There is a legend—with variations—about the discovery of cheese by an Arab trader who used this method of storing milk.
The earliest evidence of cheesemaking in the archaeological record dates back to 5500 BCE and is found in what is now Kuyavia, Poland, where strainers coated with milk-fat molecules have been found. The earliest evidence of cheesemaking in the Mediterranean dates back to 5200 BCE, on the coast of the Dalmatia region of Croatia.
Cheesemaking may have begun independently of this by the pressing and salting of curdled milk to preserve it. Observation that the effect of making cheese in an animal stomach gave more solid and better-textured curds may have led to the deliberate addition of rennet. Early archeological evidence of Egyptian cheese has been found in Egyptian tomb murals, dating to about 2000 BCE. A 2018 scientific paper stated that cheese dating to approximately 1200 BCE (3200 years before present), was found in ancient Egyptian tombs. The earliest ever discovered preserved cheese was found on mummies in Xiaohe Cemetery in the Taklamakan Desert in Xinjiang, China, dating back as early as 1615 BCE.
The earliest cheeses were likely quite sour and salty, similar in texture to rustic cottage cheese or feta, a crumbly, flavorful Greek cheese. Cheese produced in Europe, where climates are cooler than 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 respective flavors.
Ancient Greece and Rome.
Ancient Greek mythology credited Aristaeus with the discovery of cheese. Homer's "Odyssey" (8th century BCE) describes the monstrous Cyclops making and storing sheep's and goats' milk cheese (translation by Samuel Butler):
 ;templatestyles src="Template:Blockquote/styles.css" / ;We soon reached his cave, but he was out shepherding, so we went inside and took stock of all that we could see. His cheese-racks were loaded with cheeses, and he had more lambs and kids than his pens could hold...
When he had so done he sat down and milked his ewes and goats, all in due course, and then let each of them have her own young. He curdled half the milk and set it aside in wicker strainers.
Columella's "De Re Rustica" (c. 65 CE) details a cheesemaking process involving rennet coagulation, pressing of the curd, salting, and aging. According to Pliny the Elder, it had become a sophisticated enterprise by the time the Roman Empire came into being. Pliny the Elder also mentions in his writings "Caseus Helveticus", a hard Sbrinz-like cheese produced by the Helvetii. Cheese was an everyday food and cheesemaking a mature art in the Roman empire. Pliny's "Natural History" (77  CE) devotes a chapter (XI, 97) to describing the diversity of cheeses enjoyed by Romans of the early Empire. He stated that the best cheeses came from the villages near Nîmes, but did not keep long and had to be eaten fresh. Cheeses of the Alps and Apennines were as remarkable for their variety then as now. A Ligurian cheese was noted for being made mostly from sheep's milk, and some cheeses produced nearby were stated to weigh as much as a thousand pounds each. Goats' milk cheese was a recent taste in Rome, improved over the "medicinal taste" of Gaul's similar cheeses by smoking. Of cheeses from overseas, Pliny preferred those of Bithynia in Asia Minor.
Post-Roman Europe.
c. 1000, Anglo-Saxons in England named a village by the River Thames , meaning "Cheese farm".
In 1022, it is mentioned that Vlach (Aromanian) shepherds from Thessaly and the Pindus mountains, in modern Greece, provided cheese for Constantinople. Many cheeses popular today were first recorded in the late Middle Ages or after. Cheeses such as Cheddar around 1500, Parmesan in 1597, Gouda in 1697, and Camembert in 1791 show post-Middle Ages dates.
In 1546, "The Proverbs of John Heywood" claimed "the moon is made of a green cheese" ("Greene" may refer here not to the color, as many now think, but to being new or unaged). Variations on this sentiment were long repeated and NASA exploited this myth for an April Fools' Day spoof announcement in 2006.
Modern era.
Until its modern spread along with European culture, cheese was nearly unheard of in east Asian cultures and in the pre-Columbian Americas and had only limited use in sub-Mediterranean Africa, mainly being widespread and popular only in Europe, the Middle East, the Indian subcontinent, and areas influenced by those cultures. But with the spread, first of European imperialism, and later of Euro-American culture and food, cheese has gradually become known and increasingly popular worldwide.
The first factory for the industrial production of cheese opened in Switzerland in 1815, but large-scale production first found real success in the United States. Credit usually goes to Jesse Williams, a dairy farmer from Rome, New York, who in 1851 started making cheese in an assembly-line fashion using the milk from neighboring farms; this made cheddar cheese one of the first US industrial foods. Within decades, hundreds of such commercial dairy associations existed.
The 1860s saw the beginnings of mass-produced rennet, and by the turn of the century scientists were producing pure microbial cultures. Before then, bacteria in cheesemaking had come from the environment or from recycling an earlier batch's whey; the pure cultures meant a more standardized cheese could be produced.
Factory-made cheese overtook traditional cheesemaking in the World War II era, and factories have been the source of most cheese in America and Europe ever since. By 2012, cheese was one of the most shoplifted items from supermarkets worldwide.
Production.
In 2021, world production of cheese from whole cow milk was 22.2 million tonnes, with the United States accounting for 28% of the total, followed by Germany, France, Italy and the Netherlands as secondary producers (table).
As of 2021, the carbon footprint of a kilogram of cheese ranged from 6 to 12 kg of CO2eq, depending on the amount of milk used; accordingly, it is generally lower than beef or lamb, but higher than other foods.
Consumption.
France, Iceland, Finland, Denmark and Germany were the highest consumers of cheese in 2014, averaging per person per annum.
Processing.
Curdling.
A required step in cheesemaking is to separate the milk into solid curds and liquid whey. Usually this is done by acidifying (souring) the milk and adding rennet. The acidification can be accomplished directly by the addition of an acid, such as vinegar, in a few cases (paneer, queso fresco). More commonly starter bacteria are employed instead which convert milk sugars into lactic acid. The same bacteria (and the enzymes they produce) also play a large role in the eventual flavor of aged cheeses. Most cheeses are made with starter bacteria from the "Lactococcus", "Lactobacillus", or "Streptococcus" genera. 
Swiss starter cultures include "Propionibacterium freudenreichii", which produces propionic acid and carbon dioxide gas bubbles during aging, giving Emmental cheese its holes or eyes.
Some fresh cheeses are curdled only by acidity, but most cheeses also use rennet. Rennet sets the cheese into a strong and rubbery gel compared to the fragile curds produced by acidic coagulation alone. It also allows curdling at a lower acidity—important because flavor-making bacteria are inhibited in high-acidity environments. In general, softer, smaller, fresher cheeses are curdled with a greater proportion of acid to rennet than harder, larger, longer-aged varieties. 
While rennet was traditionally produced via extraction from the inner mucosa of the fourth stomach chamber of slaughtered young, unweaned calves, most rennet used today in cheesemaking is produced recombinantly. The majority of the applied chymosin is retained in the whey and, at most, may be present in cheese in trace quantities. In ripe cheese, the type and provenance of chymosin used in production cannot be determined.
Curd processing.
At this point, the cheese has set into a very moist gel. Some soft cheeses are now essentially complete: they are drained, salted, and packaged. For most of the rest, the curd is cut into small cubes. This allows water to drain from the individual pieces of curd.
Some hard cheeses are then heated to temperatures in the range of . This