RENNET
“In the making of cheese the first step is to cause the milk to curdle.
Lemon juice, vinegar, or any other acid would bring about this result,
as we have already seen; but it is customary to make use of another and
much more efficacious liquid called rennet. Let us learn first what
this liquid consists of. That calls for certain explanations apparently
foreign to our subject, but nevertheless leading directly to it.
“Among our domestic animals three, the ox, goat and sheep, are
remarkable for their horns and split hoofs. All three have a way of
eating very different from that of other kinds of animals. The dog, for
example, after masticating its food sufficiently, swallows it once for
all and passes it into a single digestive cavity called the stomach,
where it becomes a fluid mass suitable for nutrition. On the contrary,
the goat, sheep, and ox chew and swallow the same food twice; at two
different times, with a rather long interval between, the same fodder
is subjected to mastication and passed down the throat.
“Animals are characterized as ‘ruminant’ that, after chewing their food
once and letting it pass into the digestive cavity, bring it back into
the mouth for a more complete trituration. The ox, goat, and sheep are
ruminants. Instead of only one stomach they have four, that is to say
four membranous pouches where the alimentary matter passes from one to
another before being converted into a sort of nutritive soup.
“The first of these pouches is called the paunch. It is a spacious
cavity in which the animal accumulates the fodder that has been hastily
browsed and not thoroughly chewed. Its inside surface is thickly
covered with short flat filaments that give it the appearance of coarse
velvet.
“Watch the ox and sheep in the pasture. They crop the grass without
stopping, without a moment’s rest; they chew very slightly, very
hastily, and then swallow; one mouthful does not wait on another. It is
the time for filling the paunch without losing a bite by prolonged
chewing. Later, in the hours of repose, there will be leisure for
bringing up again the food swallowed and for grinding it to the proper
fineness.
“This receptacle known as the paunch having received its due supply of
fodder, the animal retires to a quiet spot, lies down in a comfortable
position, and takes up at its ease, for hours at a time, the work of
chewing. This second stage in the preparation of the food under the
millstone of the teeth is called rumination. The ox is then seen
patiently chewing, with an air of gentle satisfaction, without taking
anything from outside. What is it eating thus, when there is apparently
no fodder within reach? It is re-eating what has been stored up in the
paunch, and which now comes up from the bottom of the stomach in little
mouthfuls. Then the motion of the jaws ceases, the mouthful is
swallowed, and immediately after something round and bulging is seen
making its way upward under the skin of the neck. It is a fresh
alimentary ball coming up from the paunch to the mouth to be chewed.
Ball by ball, the mass of fodder accumulated in the paunch comes back
thus to be ground by the teeth to the right degree of fineness and then
swallowed for good.”
“That’s a clever way to eat,” was Emile’s comment. “In order not to
lose a moment of their time in the pasture, the sheep, goat, and ox do
not stop to do their chewing there: they browse without stopping and
store up a good supply. Then, lying down comfortably in the shade, they
bring up again the contents of the paunch and grind it at their ease,
little by little.”
“The second stomachic cavity is called the reticulum, its inner surface
presenting a reticulated appearance, with an arrangement of dentate and
laminate folds forming, all together, an elaborate network of meshes.
This curious formation cannot fail to strike you if you look for a
moment at a piece of tripe, one of our countless articles of food; for
what is called tripe is nothing but the collective stomach of the ox.”
“I remember having seen that beautiful honeycomb network,” said Jules,
“and the coarse velvet lining of the paunch. They were very
interesting.”
“The office of the honeycomb is to receive, in small portions, the food
already somewhat softened in the paunch, and to mold it into balls,
which rise one at a time to the ruminant’s mouth. That in fact is where
the alimentary balls are made that we see gliding from below upward,
under the skin of the neck of the ruminating ox.
“After being re-chewed to the proper fineness the food does not return
to the paunch, where it would mix with material not yet similarly
prepared; it goes to the third stomach, or manyplies, so named on
account of its numerous and wide parallel folds, having some
resemblance in arrangement to the leaves of a book.
“From the manyplies the food passes finally to a fourth and last
stomach called the rennet-bag. After this come the intestines. Now
guess whence we get that significant name of rennet, knowing as you do
what I have especially in mind in this connection?”
“You have in mind,” answered Jules, “a certain liquid, rennet, that
makes milk curdle quickly. The word rennet, or runnet, as it is also
written, must be connected with the verb run, in the sense of dropping,
coagulating. Can it be, then, that from this fourth stomach or
rennet-bag of ruminants we get the liquid rennet that is used for
curdling milk?”
“You have said it yourself,” declared Uncle Paul, much pleased at his
nephew’s clear explanation of the matter. “It is from the fourth
stomach of ruminant animals that we obtain rennet, the most efficacious
substance known for curdling milk.
“Preferably it is the rennet-bag of a young calf that is selected; then
it is cleaned carefully, salted, and dried. Thus treated, it keeps a
long time. When it is required for use, a piece as large as your two
fingers is cut off and put to soak in a glass of water or whey. The
next morning two or three spoonfuls of this liquid, called rennet, is
added to each liter of milk. In a very short time, if kept moderately
warm, the milk turns to a mass of fresh cheese.”