Rennet: Complex of Enzymes Produced in Any Mammalian Stomach

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  • Topic: Cheese, Rennet, Whey
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  • Published : April 9, 2013
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Rennet (pron.: /ˈrɛnɨt/) is a complex of enzymes produced in any mammalian stomach, and is often used in the production of cheese. Rennet contains many enzymes, including a proteolytic enzyme (protease) that coagulates the milk, causing it to separate into solids (curds) and liquid (whey). They are also very important in the stomach of young mammals as they digest their mothers' milk. The active enzyme in rennet is called chymosin or rennin (EC but there are also other important enzymes in it, e.g., pepsin and lipase. There are non-animal sources for rennet that are suitable for consumption by vegetarians. Contents [hide]

1 Production of natural calf rennet
1.1 Traditional method
1.2 Modern method
2 Alternative sources of rennet
2.1 Vegetable rennet
2.2 Microbial rennet
2.3 Fermentation-produced chymosin (FPC)
2.4 Acid coagulation
3 See also
4 References
5 External links
[edit]Production of natural calf rennet

Natural calf rennet is extracted from the inner mucosa of the fourth stomach chamber (the abomasum) of slaughtered young, unweaned calves. These stomachs are a by-product of veal production. If rennet is extracted from older calves (grass-fed or grain-fed) the rennet contains less or no chymosin but a high level of pepsin and can only be used for special types of milk and cheeses. As each ruminant produces a special kind of rennet to digest the milk of its own species, there are milk-specific rennets available, such as kid goat rennet for goat's milk and lamb rennet for sheep's milk. [edit]Traditional method

Dried and cleaned stomachs of young calves are sliced into small pieces and then put into saltwater or whey, together with some vinegar or wine to lower the pH of the solution. After some time (overnight or several days), the solution is filtered. The crude rennet that remains in the filtered solution can then be used to coagulate milk. About 1 gram of this solution can normally coagulate 2 to 4 liters of milk. This method is still used by some traditional cheese-makers in Austria, France, Greece, Italy, Romania, Switzerland, Sweden, and the United Kingdom (among others). [edit]Modern method

Deep-frozen stomachs are milled and put into an enzyme-extracting solution. The crude rennet extract is then activated by adding acid; the enzymes in the stomach are produced in an inactive form and are activated by the stomach acid. The acid is then neutralized and the rennet extract is filtered in several stages and concentrated until reaching a typical potency of about 1:15,000; meaning 1 gram of extract can coagulate 15 kg (15 litres) of milk. In 1 kg of rennet extract, there are about 0.7 grams of active enzymes – the rest is water and salt and sometimes sodium benzoate, E211, 0.5% - 1% for preservation. Typically, 1 kg of cheese contains about 0.0003 grams of rennet enzymes. [edit]Alternative sources of rennet

Because of the limited availability of mammalian stomachs for rennet production, cheese makers have looked for other ways to coagulate the milk since at least Roman times. There are many sources of enzymes, ranging from plants, fungi, and microbial sources, that can substitute for animal rennet. Cheeses produced from any of these varieties of rennet are suitable for lacto-vegetarians to consume. Fermentation produced chymosin (FPC)(see below) is used more often in industrial cheesemaking in North America and Europe today because it is less expensive and of higher quality than animal rennet.[1] [edit]Vegetable rennet

Many plants have coagulating properties. Homer suggests in the Iliad and the Odyssey that the Greeks used an extract of fig juice to coagulate milk.[2] Other examples include dried caper leaves,[3] nettles, thistles, mallow, and Ground Ivy (Creeping Charlie). Enzymes from thistle or cynara are used in some traditional cheese production in the Mediterranean. Phytic acid, derived from unfermented soybeans, or Fermentation-Produced Chymosin (FPC) may also be used. Vegetable...
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