Production of natural calf rennet
Natural calf rennet is extracted from the inner mucosa of the fourth stomach chamber (the abomasum) of young 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 mother, there are milk-specific rennets available, such as kid goat rennet especially for goat's milk and lamb rennet for sheeps milk. Rennet or digestion enzymes from other animals, like swine-pepsin, are not used in cheese production.