It is usually found in the fourth stomach chambers, called the abomasums, in ruminating animals. Rennet contains protease which curdles the milk. In morescientific circles, the active enzyme group in rennet is called chymosin.
According to both historical resources, and the course of common sense, it is understood that the first cheese was perhaps made thousands of years ago by pure chance. Possibly, our early ancestors happened to store some milk in a pouch made of animal skin—probably a kid, calf or lamb—by accident. The next day they probably discovered that the milk in the bag had curdled into curds and whey, over the course of the day. These chunks of solid curds, which could be just dried out and then preserved for long periods, were a handy derivative of plain milk which was extremely perishable without the facilities of refrigeration.
Traditionally, natural rennet is extracted by slicing the animal’s stomach into thin strips, putting them in a saltwater solution along with a little vinegar, before filtering the solution and drying out the strips. After this, it is cut into small pieces, which can be put in the milk to coagulate it. According to experts, it is best to choose the kind of rennet depending on the kind of milk being used, as calf rennet will have more of an affinity towards cow’s milk and so on.
While animal rennet is the preferred choice for master cheese-makers, it is quite expensive as it is difficult to find an adequate supply of appropriate stomachs. Some modern-day alternatives include vegetable-derived rennet, or genetically engineered and synthesized rennet.
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Rennet is an essential ingredient in the making of cheese. Rennet helps in the coagulation of the raw material—milk—into solid curds and milky whey.
Rennet, while traditionally extracted from plants and animals, is available today in a variety of forms, from liquids to tablets, to genetically engineered artificially synthesized rennet.
Rennet is a naturally occurring enzyme which is produced in the stomachs of young mammals to be able to digest their mother’s milk.
Plant rennet is produced from the fig tree, or the ground-ivy called Creeping Charlie (Glechoma hederacea). Plant rennet, however, is produced in a limited fashion, with no commercial manufacturing, so to say.
Molds like Rhizomucor miehei are used as microbial rennet. This microbial rennet is considered to be suitable for vegetarians.
Cheese made using microbial rennet, however, tends to have a slightly bitter taste, which may or may not be to one’s particular liking.
From about 1990 onwards, scientists have been able to produce genetically engineered rennet in the laboratories.
While giving the obvious advantage of being much cheaper to produce, GM rennet preserves the qualities and properties of natural calf rennet because it has been produced by the using calf genes to modify particular bacterial or fungus cultures to produce the required chymosin.
According to some sources, almost 6 out of 10 hard cheeses made in the US today are manufactured using GM rennet.
Rennet is sold in the market in the form of both liquids as well as tablets.
For making smaller quantities of cheese, tablets may be used, but for industrial production most manufacturers prefer using the liquid, because it has better dissolving properties than the solid tablet rennet.
I have use both tablets and liquid, but liquid is what I use today, even for smaller batches of homemade cheese.
Rennet In Cheese Making: Tablets or Liquid?