In order to make clear certain points in regard to the nature and
occurrence of ham souring and to insure a better understanding of the
experiments which are to be described later, it would seem best to
begin with a brief outline of the method of curing hams as practiced in
the larger packing establishments of the country. This description is
merely a general outline of the method of preparing hams for cure and
the method of handling hams while in cure, and deals chiefly with those
points that bear on the question of souring.
After the slaughtered animal has been cleaned, scraped, eviscerated,
washed, and split down the middle, the carcass is usually allowed to
hang for an hour or so in a large room open to the outside air, known
as the “hanging floor.” This is done with a view to getting rid of a
certain amount of the body heat before the carcass is run into the
chill rooms, and effects a saving in refrigeration.
The carcasses are next run into “coolers” or chill rooms, and subjected
to refrigeration with a view to ridding them entirely of their body
heat. The coolers are large rooms fitted with brine pipes and capable
of accommodating several hundred carcasses. The temperature of the
coolers when the carcasses are run in is about 32° F. When filled, the
temperature of the cooler rises to about 45° F., owing to the heat
given off from the carcasses. The temperature is then gradually reduced
to 28 or 30° F. Hog carcasses are left in the coolers as a rule for
forty-eight hours, at the end of which time they are stiff and firm,
but not frozen. The temperature of the chill rooms is always carefully
watched, thermometer readings being made every few hours and duly
recorded. The temperature of the carcasses is always tested when they
leave the chill room. In those plants provided with a hanging floor, a
certain number of the carcasses are also tested before they are sent to
the chill rooms in order to determine the amount of heat lost on the
hanging floor.
The carcasses are tested by means of an especially constructed
thermometer, known as a “ham thermometer,” which has a pointed metal
protector so that it can be thrust into the body of the ham. (See fig.
4.) The ham has been rightly selected as the proper portion of the
carcass at which to take the temperature, as it constitutes the largest
mass of muscular tissue in the carcass and holds the body heat longer
than any other portion. In taking the temperature, the thermometer
is thrust deep into the body of the ham so that the point of the
thermometer rests alongside or a little behind the upper portion of the
femur or middle bone, the latter being used as a guide in introducing
the thermometer. A certain number of the carcasses from each cooler
are tested in this way as a check on the refrigeration. The inside
temperature of the hams when they leave the chill rooms should be about
34° F.
The carcasses are next cut up and the hams trimmed for pickling. In
some houses the hams are given an additional chilling of 48 hours after
they are cut from the carcasses, but this is not done as a rule, nor
does it seem to be necessary.
The hams are now sent to the pickling rooms, or “sweet pickle
department,” as this branch of the packing house is designated, and
here a certain number are again tested with a thermometer, as described
above. This test is carried out by the foreman in charge of the sweet
pickle department in order that he may satisfy himself that the
hams are properly chilled before they go into the pickle and as an
additional check on the refrigeration.
The hams are now ready to be “pumped,” and this pumping, as will be
shown later, constitutes an important step in a successful cure.
Pumping consists in forcing a strong brine solution containing
saltpeter into the muscular tissues of the ham, and is accomplished by
means of a large, hollow, fenestrated needle connected by means of a
rubber hose with a powerful hand pump. The needle is introduced along
the bone, the latter being used as a guide.
In all of the larger packing establishments two general methods of
curing hams are followed, the two methods being designated as the
“fancy” or “mild cure” and the “regular cure,” the term “cure” being
used to designate the curing period. Various trade names are given
by the different packing establishments to the hams cured by these
methods. In the fancy cure the hams are pumped in the shank only,
whereas in the regular cure they are pumped in both body and shank.
The same pumping pickle is generally used for the two cures. It is a
significant fact that the greater proportion of the “sours” are found
among the fancy or mild cure hams. This point will be discussed farther
on in connection with some experiments to be described later.
The actual curing is usually carried out in large vats which hold about
1,400 pounds of meat or some hundred hams. The hams are packed in the
vats in layers and are entirely covered with the pickling solution or
brine. A certain proportion is always observed between the weight of
the meat and the amount of the solution. The pickling solution, or
“pickle,” as it is termed, is a brine solution containing saltpeter
and sugar. The composition of the pickle varies somewhat with the
different packing establishments. The fancy-cure hams are usually cured
in a milder pickle, that is, one that contains less salt and saltpeter
than the pickle used in the regular cure, although in some packing
establishments the same curing pickle is used for the two cures, the
only difference being the additional pumping given the regular-cure
hams. The pickling rooms, or “cellars,” as they are called, are held at
a temperature of 34° to 36° F., and the pickling solutions are always
chilled to this temperature before being used.
The hams are allowed to remain in cure for about 60 days, and during
this time are “overhauled” several times. Overhauling consists in
throwing the hams from the vat in which they are packed into a
neighboring empty vat, and then transferring the pickle to the new vat.
The pickle is not changed, and the same pickle follows the hams through
the entire curing process. The object in overhauling is to stir up the
pickle and expose fresh surfaces of the meat to its action.
Hams are also cured in tierces which hold about 300 pounds of meat.
In the tierce cure, the hams are packed in the tierces, the latter
are then headed up, the pickling solution is next run in through the
bunghole, so as to fill the tierce entirely, and a wooden stopper is
finally driven into the bunghole. The tierces are rolled back and forth
across the floor on dates corresponding to the dates of overhauling in
the vat cure. The object of the rolling is to stir up the pickle, and
in this way it corresponds to overhauling in the vat cure.