Rennet
Encyclopedia
Rennet is a complex of enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s produced in any mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

ian stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

 to digest the mother's milk, and is often used in the production of cheese
Cheese
Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....

. Rennet contains many enzymes, including a proteolytic enzyme (protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....

) that coagulates the milk, causing it to separate into solids (curds) and liquid (whey
Whey
Whey or Milk Serum is the liquid remaining after milk has been curdled and strained. It is a by-product of the manufacture of cheese or casein and has several commercial uses. Sweet whey is manufactured during the making of rennet types of hard cheese like cheddar or Swiss cheese...

). They are also very important in the stomach of young mammals as they digest their mothers milk. The active enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 in rennet is called chymosin
Chymosin
Chymosin or rennin is an enzyme found in rennet. It is produced by cows in the lining of the abomasum...

or rennin but there are also other important enzymes in it, e.g., pepsin
Pepsin
Pepsin is an enzyme whose precursor form is released by the chief cells in the stomach and that degrades food proteins into peptides. It was discovered in 1836 by Theodor Schwann who also coined its name from the Greek word pepsis, meaning digestion...

 and lipase
Lipase
A lipase is an enzyme that catalyzes the formation or cleavage of fats . Lipases are a subclass of the esterases.Lipases perform essential roles in the digestion, transport and processing of dietary lipids in most, if not all, living organisms...

. There are non-animal sources for rennet that are suitable for consumption by vegetarians
Vegetarianism
Vegetarianism encompasses the practice of following plant-based diets , with or without the inclusion of dairy products or eggs, and with the exclusion of meat...

.

Production of natural calf rennet

Natural calf
Calf
Calves are the young of domestic cattle. Calves are reared to become adult cattle, or are slaughtered for their meat, called veal.-Terminology:...

 rennet is extracted from the inner mucosa of the fourth stomach chamber (the abomasum
Abomasum
The abomasum, also known as the maw, and the rennet-bag, and the read, is the fourth and final stomach compartment in ruminants. It secretes rennin - the artificial form of which is called rennet, and is used in cheese creation....

) of slaughtered young, unweaned calves. These stomachs are a by-product
By-product
A by-product is a secondary product derived from a manufacturing process or chemical reaction. It is not the primary product or service being produced.A by-product can be useful and marketable or it can be considered waste....

 of veal
Veal
Veal is the meat of young cattle , as opposed to meat from older cattle. Though veal can be produced from a calf of either sex and any breed, most veal comes from male calves of dairy cattle breeds...

 production. If rennet is extracted from older calves (grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...

-fed or grain
GRAIN
GRAIN is a small international non-profit organisation that works to support small farmers and social movements in their struggles for community-controlled and biodiversity-based food systems. Our support takes the form of independent research and analysis, networking at local, regional and...

-fed) the rennet contains less or no chymosin but a high level of pepsin and can only be used for special types of milk
Milk
Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...

 and cheese
Cheese
Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....

s. As each ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...

 produces a special kind of rennet to digest the milk of its own species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, there are milk-specific rennets available, such as kid goat rennet for goat
Goat
The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...

's milk and lamb
Domestic sheep
Sheep are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Although the name "sheep" applies to many species in the genus Ovis, in everyday usage it almost always refers to Ovis aries...

 rennet for sheep's milk.

Traditional method

Dried and cleaned stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

s of young calves are sliced into small pieces and then put into saltwater or whey
Whey
Whey or Milk Serum is the liquid remaining after milk has been curdled and strained. It is a by-product of the manufacture of cheese or casein and has several commercial uses. Sweet whey is manufactured during the making of rennet types of hard cheese like cheddar or Swiss cheese...

, together with some vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

 or wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

 to lower the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 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 liter
Litér
- External links :*...

s of milk.

This method is still used by some traditional cheese-makers, e.g. in Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

, Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, Romania
Romania
Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...

, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 and Alp-Sennereien in Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

.

Modern method

Deep-frozen stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

s are milled and put into an enzyme-extracting solution. The crude rennet extract is then activated by adding acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

; the enzymes in the stomach are produced in an inactive form and are activated by the stomach acid. The acid is then neutralized
Neutralization
In chemistry, neutralization, or neutralisation is a chemical reaction in which an acid and a base react to form a salt. Water is frequently, but not necessarily, produced as well. Neutralizations with Arrhenius acids and bases always produce water:Y and X represent a monovalent cation and anion...

 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 litre
Litre
pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...

s) of milk.

In 1 kg of rennet extract, there are about 0.7 gram
Gram
The gram is a metric system unit of mass....

s of active enzymes – the rest is water and salt and sometimes sodium benzoate
Sodium benzoate
Sodium benzoate has the chemical formula NaC6H5CO2; it is a widely used food preservative, with E number E211. It is the sodium salt of benzoic acid and exists in this form when dissolved in water. It can be produced by reacting sodium hydroxide with benzoic acid.-Uses:Sodium benzoate is a...

, E211,
0.5% - 1% for preservation. Typically, 1 kg of cheese contains about 0.0003 grams of rennet enzymes.

Alternative sources of rennet

Because of the limited availability of proper stomachs for rennet production, cheese makers have looked for other ways to coagulate the milk since at least Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 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
Lacto vegetarianism
A lacto vegetarian diet is a vegetarian diet that includes dairy products such as milk, cheese, yogurt, butter, cream, and kefir, but excludes eggs. Lacto-vegetarians also abstain from cheeses that include animal rennet and yogurts that contain gelatin...

 to consume. GMO-Microbial rennet (see below) is used more often in industrial cheesemaking in North America today because it is less expensive than animal rennet, whereas cheese from Europe is more likely to be made from animal rennet due to tradition.

Vegetable rennet

Many plants have coagulating properties. Homer
Homer
In the Western classical tradition Homer , is the author of the Iliad and the Odyssey, and is revered as the greatest ancient Greek epic poet. These epics lie at the beginning of the Western canon of literature, and have had an enormous influence on the history of literature.When he lived is...

 suggests in the Iliad
Iliad
The Iliad is an epic poem in dactylic hexameters, traditionally attributed to Homer. Set during the Trojan War, the ten-year siege of the city of Troy by a coalition of Greek states, it tells of the battles and events during the weeks of a quarrel between King Agamemnon and the warrior Achilles...

 that the Greeks used an extract of fig
Ficus
Ficus is a genus of about 850 species of woody trees, shrubs, vines, epiphytes, and hemiepiphyte in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending into the semi-warm temperate zone. The Common Fig Ficus is a genus of...

 juice to coagulate milk. Other examples include dried caper leaves
Caper
Capparis spinosa, the caper bush, is a perennial winter-deciduous species that bears rounded, fleshy leaves and large white to pinkish-white flowers. A caper is also the pickled bud of this plant...

, nettles, thistle
Thistle
Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles often occur all over the plant – on surfaces such as those of the stem and flat parts of leaves. These are an adaptation that protects the...

s, mallow
Malva
Malva is a genus of about 25–30 species of herbaceous annual, biennial, and perennial plants in the family Malvaceae , one of several closely related genera in the family to bear the common English name mallow. The genus is widespread throughout the temperate, subtropical and tropical regions of...

, and Ground Ivy
Glechoma hederacea
Glechoma hederacea is an aromatic, perennial, evergreen creeper of the mint family Lamiaceae. It is commonly known as Ground-ivy, gill-over-the-ground or Creeping Charlie. It has numerous medicinal uses, and is commonly used as a tasty salad green in many countries...

 (Creeping Charlie). Enzymes from thistle or cynara
Cynara
Cynara is a genus of about 10 species of thistle-like perennial plants in the family Asteraceae, originally from the Mediterranean region, northwestern Africa, and the Canary Islands....

are used in some traditional cheese production in the Mediterranean. Phytic acid, derived from unfermented soybeans, or genetically modified (GM) soy rennet may also be used.

These real vegetable rennets are also suitable for vegetarians. Vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....

 rennet might be used in the production of kosher
Kosher foods
Kosher foods are those that conform to the regulations of the Jewish Halakhic law framework, kosher meaning fit or allowed to be eaten. A list of some kosher foods are found in the book of Leviticus 11:1-47. There are also certain kosher rules found there...

 and halal cheeses but nearly all kosher cheeses are produced with either microbial rennet or genetically modified rennet. Worldwide, there is no industrial production for vegetable rennet. Commercial so-called vegetable rennets usually contain rennet from the mold
Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...

 Mucor miehei - see microbial rennet below.

Microbial rennet

Some molds such as Rhizomucor miehei
Rhizomucor miehei
Rhizomucor miehei is a species of fungus. It is commercially used to produce enzymes which can be used to produce a microbial rennet to curd milk and produce cheese.-External links:* listing...

are able to produce proteolytic enzymes. These molds are produced in a fermenter and then specially concentrated and purified to avoid contamination with unpleasant byproducts of the mold growth. At the present state of scientific research, governmental food safety organizations such as the European Food Safety Authority
European Food Safety Authority
The European Food Safety Authority is an agency of the European Union that provides independent scientific advice and communication on existing and emerging risks associated with the food chain, created by European Regulation 178/2002....

 deny QPS (Qualified Presumption of Safety) status to enzymes produced especially by these mold
Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...

s.

The flavor and taste of cheeses produced with microbial rennets tend towards some bitterness, especially after longer maturation periods. These so-called "microbial rennets" are suitable for vegetarians, provided no animal-based alimentation was used during the production.

Genetically engineered rennet

Because of the above imperfections of microbial rennets, some producers sought further replacements of natural rennet. With the development of genetic engineering, it became possible to insert cow genes into certain bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, fungi or yeasts to make them produce chymosin
Chymosin
Chymosin or rennin is an enzyme found in rennet. It is produced by cows in the lining of the abomasum...

. Chymosin produced by genetically modified organisms was the first artificially produced enzyme to be registered and allowed by the US Food and Drug Administration. In 1999, about 60% of US hard cheese was made with genetically engineered chymosin
and it has up to 80% of the global market share for rennet.
By 2008, approximately 80% to 90% of commercially made cheeses in the US and Britain were made using GM-based rennet. One example of a commercially available genetically engineered rennet is Chymax
Chymax
Chymax is a bio-engineered rennet substitute used in cheeses developed by Pfizer and marketed by Chr. Hansen. It contains a synthetic version of chymosin, an enzyme that causes milk to curdle. It is produced by a variety of mold and is generally recognized as not being an animal derived product and...

, created by Pfizer
Pfizer
Pfizer, Inc. is an American multinational pharmaceutical corporation. The company is based in New York City, New York with its research headquarters in Groton, Connecticut, United States...

. Today, the most widely used genetically engineered rennet is produced by the fungus Aspergillus niger
Aspergillus niger
Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food...

.

Cheese production with genetically engineered rennet is similar to production with natural calf rennet. GMO-produced rennet contains only one of the known main chymosin types, either type A or type B. Other chymosin types found in natural rennet do not exist in GMO-produced rennet.

Often, a mixture of genetically engineered chymosin and natural pepsin is used to imitate the complexity of natural rennet and to get the same results in coagulation and in development of flavour and taste.

The so-called "GM rennets" are suitable for vegetarians if there was no animal-based alimentation used during the production in the fermenter. However, genetically engineered rennet is often produced from soy or phytic acid, which is unsuitable for people who have soy-based allergies
Allergy
An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...

.

Acid coagulation

Milk can also be coagulated by adding an acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

, such as citric acid
Citric acid
Citric acid is a weak organic acid. It is a natural preservative/conservative and is also used to add an acidic, or sour, taste to foods and soft drinks...

.

Cream cheese
Cream cheese
Cream cheese is a soft, mild-tasting, white cheese with a high fat content. Traditionally, it is made from unskimmed milk enriched with additional cream....

, paneer
Paneer
Paneer is a fresh cheese common in South Asian cuisine. It is of Indian origin. In eastern parts of India, it is generally called Chhena...

, and rubing are traditionally made this way (see :Category:Acid-set cheeses for others).
The acidification can also come from bacterial fermentation such as in cultured milk.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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