Acid microbes are inherent in the lacteal structure and come dormant
in the milk from the udder. As soon as they feel the atmosphere
they spring into spontaneous activity, however retarded by cold or
fostered by heat. Acid in milk is a species of yeast fermentation and
is the first step toward decomposition. It is the best servant the
cheese maker has and is also his worst enemy when the relation is
changed to that of master. In a temperate climate, in hay produced
milk, in the spring of the year, acid is nearly dormant and there
is but little use for it. Hay cheese are expected to be thrown on
the market in cool weather when they will be quickly consumed;
therefore, the additional firmness given by acid is not required
to be applied as a safeguard against heat. If early hay cheese are
cooked enough and salted about two pounds to the thousand, it is all
that is desirable. On the border between hay and grass the weather
is gradually moderating and there is torrid temperature in sight in
the immediate future. Acid now begins to appear in the whey and curd
you are working by the time you have it scalded. It has a right to
be there for it is your friend and you now need its timely proffered
assistance. If, through unusually good quality of milk, it does not
come to the front, coax it a little in the following way: After the
curd is cooked and before whey is drawn, turn on steam and re-warm
the whole mass, then draw the whey and pack the curd in bulk as much
as possible, covering it up with a cloth. This will soon set the acid
to working in good shape. Always rely on the hot iron test to locate
acid. It takes an expert to get the amount of acid even from mess
to mess by an olfactory measurement. On March and the first half of
April stock I do not care for any acid to show, but on later April
and beginning of May goods acid should show on the hot iron clearly
and perceptibly. When the curd is pressed to the metal, fine strings
should just start from it immediately prior to salting. At this time
you want just a little acid but not too much—too much will surely
spoil spring made cheese.
The question arises, “How far must a cheese maker probe into the
hidden mysteries that shroud the digestive assimilation of the
product he manufactures?” We answer that he cannot probe too deeply
or extend his researches too far into the minute. There are too many
makers now with only a superficial knowledge of their craft, and
before there can be any perceptible elevation of quality in American
cheese the shoes of these novices must be filled by such men as we
now term “experts.” Take, for example, the subject of acid which
we are here discussing. A maker who can perceive it only as it is
revealed by stringing on the iron is not competent to be in charge
of a factory, for anybody could detect it there. The development of
lactic acid is a species of fermentation induced by the spontaneous
increase of inherent minute bacteria. It takes the same experience
to perceive and govern it in milk and cheese as it does practice
with square and compass to become a carpenter. We cannot _tell_ you
all about it—it will take many days of careful observation and fine
testing to understand its nature enough to make it your servant
in the cheese making art. That is why makers without practical
experience are always incompetent. Hold curd in the whey until it
shows at least a quarter of an inch of acid by the hot iron and then
draw off whey as quickly as possible. It is always a good plan where
you have large vats and they are pretty well filled to have a third
of the whey drawn off before acid develops, for then you can more
quickly lay bare your curd. As the whey recedes, push the curd with
the rake head toward the upper end of the vat and then tip the vat
down, so that the whey will flow out from the lowest corner. Make
a gutter with your hands through the center of the curd mass and
distribute it in an even pack on each side of the vat. Now, take a
knife and cut it into strips eight inches wide, drawing the knife
from the center gutter toward the side of the vat. Flop these strips
upside down and, to farther facilitate drainage, cut a longitudinal
canal next to the sides of the vat. Examine by the iron and see how
the curd is working as to acid; if it is maturing slowly and the curd
is not hot, shut off all draughts of air, cut the curd into “bricks”
or blocks the size of a brick, and scatter them over the bottom of
the vat. Then cover the vat up with the same cloth that you used
when scalding. If, on the other hand, the curd is hot and maturing
rapidly, cut into small bricks, scatter well and give it all the
air possible, frequently turning the bricks over. Unless positively
unavoidable on account of overplus of acid never grind curd until
you have cooled it down to a temperature of 80°. Above that heat the
fine texture of the curd is torn and mutilated so that it will give
out white whey, and, as a consequence, waste of quality and substance
ensues.
The curd being first well drained and cooled to 80° by subdivision
of pieces and having also developed acid sufficient for the season,
it is ready for the mill. Grind with deliberation, and if you have a
self-salter, so much the better. Incorporate the salt into the curd
by thorough, although not violent, mixing and then air your curd.
This is one of the most important processes of all and yet the one
most neglected by negligent makers. A curd requires airing, not so
much to expel heat as to expunge the gaseous odors that have followed
it down from its animal origin. Stir it well at frequent intervals
and spread it out well over the surface of the vat. So calculate that
it can lay twenty minutes or half an hour before it has sunk to the
temperature of 70°, when it is just right for the hoops. Allowing it
to lay this length of time gives the salt an opportunity to strike
into the pores and impregnate the product with its saline properties
before being put under pressure.