Rennet /ˈrɛnɨt/ is a complex of
enzymes produced in
stomachs of
ruminant mammals which is used in the production of most
cheeses.
Chymosin, its key component, is a
protease enzyme that
curdles the
casein in
milk, helping young mammals digest their mothers' milk. It can also be used to separate milk into solid
curds used for cheesemaking and liquid
whey. In addition to chymosin, rennet contains other important enzymes in it such as
pepsin and a
lipase. There are non-animal sources for rennet that are suitable for consumption by
vegetarians.
Production of natural calf rennet[
edit]
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.
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 be a 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.[sup]
[1][/sup]
Vegetable rennet[
edit]
Many plants have coagulating properties.
Homer suggests in the
Iliad that the Greeks used an extract of
fig juice to coagulate milk.[sup]
[2][/sup] Other examples include
dried caper leaves,[sup]
[3][/sup]
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 rennets are also suitable for
vegetarians.
Vegetable rennet might be used in the production of
kosher and
halal cheeses but nearly all kosher cheeses are produced with either microbial rennet or FPC.[sup][
citation needed][/sup] Worldwide, there is no industrial production for vegetable rennet. Commercial so-called vegetable rennets usually contain rennet from the
mold Mucor miehei - see microbial rennet below.
1.
Citric Acid can
be substituted – it will adjust the acidity (lower the pH) of the fruit, which is
what you want to do. 1/4 teaspoon powdered
Citric Acid is equivalent to 1 Tablespoon lemon juice. 1 teaspoon powdered
Citric Acid is equivalent to ¼ cup lemon juice (4 Tablespoons).
