Part 4

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.

DEFINITION OF SOURING.

To the meat inspector, a sour ham is one which has a tainted or “off” odor, that is, any odor which deviates from the normal. The odor may be very slight, so slight that at times only the trained meat inspector can detect it. When slight, the odor is elusive and hard to define, but when pronounced it has a distinctly putrefactive quality. When not very pronounced, the odor possesses, as a rule, a slightly sour quality, chemically speaking, and at times this sour quality may be quite marked; hence the term “sour ham,” or “sour” has originated. In a badly soured ham—using the term “sour” in the packing-house sense to denote any ham that is tainted—the odor loses this sour quality and becomes distinctly putrefactive in nature.

CLASSIFICATION OF SOUR HAMS AND LOCATION OF SOUR AREAS.

Sour hams are classed as “shank sours” and “body sours,” according to the location of the souring, and these may be “light” or “heavy.” When the souring is very pronounced, the ham is termed a “stinker.”

Souring appears to start, as a rule, around the stifle joint (femorotibial articulation), and extends upward into the body of the ham.

In quite a large proportion of the hams which are sour in the body—probably from 40 to 50 per cent—the souring extends through to the bone marrow of the femur or middle bone, and the sour odor is at times more pronounced in the bone marrow than in the meat. The odor of the bone marrow, when pronounced, is strongly suggestive of a dissecting-room odor, and is distinctly putrefactive in quality.

In the case of light body sours the sour odor is confined to a small area immediately around the bone, and may be so slight that it is detected only with difficulty. In such hams the bone marrow is apt to be sweet, and it is not until the souring becomes more extensive that the bone marrow becomes involved.

The distribution of the sour area in the body of a well-developed sour is shown in figure 1.

In the case of a well-developed body sour the sour area is more pronounced near the bone, as represented in figure 1 by the shaded area, and may extend out into the body of the ham for a variable distance, according to the degree of souring, as represented by the dotted lines, gradually fading off toward the margins, where it may be imperceptible or entirely wanting.

In the pronounced sours, termed “stinkers,” the odor pervades the entire ham, and is of a distinctly putrefactive quality.

In shank sours, the souring is more or less confined to the shank, or the region about the tibio-femoral articulation, but may extend upward into the lower portion of the body of the ham.

METHOD OF DETECTING SOUR HAMS.

Souring is detected and located by means of a pointed metal instrument known as a “ham trier,” which resembles a long, slightly flattened ice pick. The trier is thrust into the ham at different points along the bone, rapidly withdrawn, and the odor which clings to the metal noted. The trained inspector works very rapidly, and is able to detect even the slightest sour or off odor which might be imperceptible to one not trained to the work. At the end of the cure all hams are tested with the trier under the supervision of Government meat inspectors.

Hams are also given what is called the “30-day inspection” by plant inspectors during the process of curing. An average ham weighing from 14 to 16 pounds requires about 60 days to cure, and at the end of 30 days a certain number of hams in each run are usually tested to see how the cure is progressing. If no sour hams are discovered at this inspection the packer knows that the cure is progressing satisfactorily, and moreover he feels sure that his hams will finish satisfactorily, for experience has taught him that souring develops within the first four weeks of the curing period, and if his hams are sweet at the end of this time, he can feel practically sure that no sours will develop later on.

THEORIES IN REGARD TO HAM SOURING.

The theories as to the cause of souring are many and varied. The majority of them are pure speculation and have no foundation upon observed facts. A few of these theories may be enumerated to show how wide and varied has been the speculation upon this subject.

A theory which is quite prevalent among packing-house employees attributes souring to overheating of the animal previous to slaughter, but tests were made by driving hogs to the point of exhaustion just prior to slaughter and curing the hams from these animals in comparison with hams taken from animals which had been rested prior to slaughter, with no difference in the cured product; that is, the hams taken from overheated hogs cured equally as well as those taken from rested hogs.

Another theory attributes souring to a diseased condition of the meat. Prior to the enforcement of the Federal regulations governing meat inspection there might have been some ground for such a supposition, but this theory could not hold at the present time, in view of the thorough and efficient inspection now in force, for it can be safely said that no diseased meat now passes the Government inspectors, and therefore no diseased meat goes into cure in inspected houses. In order to test this theory, however, hams were secured from a number of condemned animals which showed various diseased conditions, such as hog cholera, pyemia, septicemia, scirrhous chord, etc., and these hams were cured in comparison with hams taken from normal hogs. It was found that the hams taken from the diseased hogs cured equally as well as those taken from healthy hogs. The hams from the diseased hogs were destroyed after the experiment, as the meat taken from diseased animals was of course not considered fit for consumption, the object of the experiment being merely to determine whether or not souring is caused by diseased conditions.

Another theory attributes souring to imperfect or too rapid chilling of the meat before it is put in pickle, and places the blame upon the refrigeration. According to this theory, souring results when the meat is chilled too suddenly, the idea being that by the rapid congealing of the juices of the meat a coating is formed on the outside of the ham whereby the animal heat is prevented from escaping from the interior, leaving the meat next to the bone at a higher temperature than the outside of the ham.

In order to test this last theory, a number of hog carcasses were run direct from the killing floor to a cooler at 28° F. and a like number of carcasses of the same average weight which had been allowed to stand for two hours at the outside temperature of the air (53° F.) were placed in the same cooler. The carcasses which had hung for two hours in the air had lost an average of 14 degrees in temperature before going to the cooler. The temperature of the cooler rose to 29° F. after the carcasses were put in, but was soon reduced to 28° F. and held at this temperature. The temperatures of the hams were taken at the end of 24 hours, and practically no difference was found in the inside temperatures of the two lots; that is, the hams on the hot carcasses which were subjected to a sudden chilling exhibited practically the same inside temperature (i. e., next to the bone) as those which had cooled for two hours at the temperature of the air before being placed in the cooler.

Still another theory attributes souring to lack of penetration of the pickling fluids, but analyses of sour and sound hams do not seem to bear out this theory. The rate of penetration of the pickling fluids, however, would seem to have some bearing on the subject, and this point will be discussed later in connection with some laboratory experiments on the inhibitory effects of sodium chlorid and potassium nitrate.

So much for the more commonly accepted theories which have been advanced to explain ham souring.

PREVIOUS EXPERIMENTAL WORK TO DETERMINE CAUSE OF HAM SOURING.

A review of the literature reveals but one article bearing directly on the subject of the cause of ham souring.

In June, 1908, Klein published in the London Lancet an article on “miscured” hams. He describes a miscured ham as one which has a distinctly putrid smell, and the tainted areas he describes as varying in color from a dirty gray to a dirty green, the muscular tissues in the strongly tainted areas being swollen and soft, or jelly-like. From such hams he isolated a large nonmotile, nonspore-bearing, anaerobic bacillus which he calls Bacillus fœdans. He cultivated the organism on different media and obtained from the cultures a putrid odor resembling that of the ham from which the culture was obtained, but did not attempt to produce tainting by injecting sound hams with the bacillus.