As it has been shown that souring in hams results from the growth
of a bacterium which is introduced into the bodies of the hams in
the various manipulations which the hams undergo, the only way to
eliminate souring in hams, as they are cured in the larger packing
establishments, would be to cure the hams under aseptic or sterile
conditions, which would, of course, be a physical impossibility.
While it will probably be impossible, therefore, to eliminate souring
entirely under the methods of ham curing which are at present employed
in the larger packing establishments, much can undoubtedly be done
toward reducing the percentage of sours. In the matter of taking ham
temperatures, for instance, if the thermometers used were thoroughly
cleaned and disinfected and the surfaces of the hams seared at the
point where the thermometer is introduced, infection from this source
could be entirely prevented; or it might be possible so to regulate
the temperature of the chill rooms that the taking of ham temperatures
could be discontinued.
The elimination of the souring that results from the introduction of
foreign matter on the pumping needles could be effected in two ways
only, (1) by not pumping the hams at all, or (2) by pumping them under
sterile or aseptic conditions. As has been stated before, some of the
smaller packing establishments cure their hams without pumping, and in
these establishments the percentage of sours runs very low. When hams
are cured without pumping, however, the period of curing has to be
materially lengthened in order to give the curing pickles sufficient
time to penetrate thoroughly, and this is what the larger plants wish
to avoid because of the greater space and greater number of vats which
would be necessitated. The object of pumping in the larger plants,
where the number of hams handled daily runs into the thousands, is to
hasten the cure and thus prevent the accumulation of a great number of
hams at one time. It is doubtful, therefore, whether the larger packing
houses could conveniently discontinue pumping.
To pump the hams under aseptic conditions would necessitate a technique
far too elaborate for routine use in the packing house; in fact,
anything like complete asepsis would be out of the question. Certain
measures might be adopted, however, that would tend to prevent the
possible introduction of ham-souring bacilli in the process of pumping.
It would undoubtedly be safer, for instance, to boil the pumping pickle
before use, and the chances of carrying in contaminated foreign matter
on the pumping needles could be lessened by sterilizing the pumps and
needles with boiling water and by frequently dipping the needles, while
in use, in boiling water. If the hams were sprayed with clean water
just prior to pumping, there would be less likelihood of carrying in
foreign matter on the needles. The danger of introducing contaminated
foreign matter on the needles might be further obviated by searing the
surfaces of the hams at the points where the needles are introduced;
but such a procedure would be hardly practicable in the larger packing
houses, where the great number of hams cured necessitates rapid
handling.
While the danger of possible contamination in pumping, through the
introduction of contaminated foreign matter on the pumping needles,
can not well be avoided, this danger is partly counterbalanced by the
inhibitory action of the pumping pickle, which is strikingly shown in
the experiments which have been described. In these experiments, 100
hams received large doses of the ham-souring bacillus, half of these
hams being subjected to the mild cure and half to the regular cure,
with the following result: In the case of the mild-cure hams, which
were pumped in the shank only, the percentage of sours was practically
100 per cent, every ham with possibly one exception becoming sour;
whereas in the regular-cure hams, which were pumped in both body and
shank, only 58 per cent of the hams became sour. In other words, the
additional pumping which the regular-cure hams received served to
prevent souring in 42 per cent of these hams. In these experiments the
number of bacteria introduced into the hams was very great, thousands
and even millions of the bacilli being introduced into each ham,
whereas in the routine of the packing house it is not likely that
more than a few of the bacilli are ever introduced at one time on the
thermometers and pumping needles. In view of these results it is safe
to say that in the larger packing houses, where pumping seems to be
necessary, the number of sours could be reduced fully 50 per cent if
all hams were pumped in the body as well as in the shank.
At present the usual procedure is to pump all hams, both mild and
regular cure, with the same pumping pickle, the mild-cure hams being
pumped in the shank only and the regular-cure hams at two additional
points in the body. The experiments quoted above show that the
additional pumping which the regular-cure hams receive undoubtedly
tends to prevent the development of souring in these hams, and this
result is unquestionably due to the inhibitory action of the salts
contained in the pumping pickle, as it was found by laboratory
experiment that the addition of 3 per cent of sodium chlorid to
culture media is sufficient to inhibit the growth of the ham-souring
bacillus. The pumping pickles consist of strong brine solutions and
always contain considerably more than 3 per cent of sodium chlorid.
If, therefore, the pumping of regular-cure hams were made more
thorough than at present, and all of the deeper portions of the ham
were thoroughly saturated with the strong brine solution, souring
could be largely eliminated, if not entirely prevented, in these hams,
as an unfavorable medium or soil would thus be created in which the
ham-souring bacillus could not develop. The ham-souring bacillus is
able to develop within the bodies of the regular-cure hams because the
pumping of these hams is not always thorough and there are certain
areas in the inner or deeper portions of the hams in which the tissues
are not thoroughly saturated with the pumping pickle.
Under the present methods of curing, the greater proportion of the
sours occur among the partly pumped or mild-cure hams. These hams are
pumped in the shank only, and the growth of the ham-souring bacillus
within the bodies of these hams is not interfered with until the curing
pickle has penetrated from the outside. As it requires several weeks
for the curing pickle to penetrate thoroughly into the deeper portions
of these hams, the bacillus is thus afforded a considerable interval
in which to develop before it is exposed to the inhibitory action of
the pickle. If these hams could be thoroughly pumped in the body at
the beginning of the cure in the same manner as the regular-cure hams,
the chief loss from ham souring would be eliminated. It would not do,
however, to pump these hams in the body with the same pumping pickle
used in the regular cure, as the meat would be rendered too salty and
the mild flavor of the ham would be lost. There is undoubtedly a demand
for mild-cure hams, otherwise they would not be on the market; and the
question then arises how to pump these hams and still retain a mild
cure. This might be accomplished by pumping these hams with their own
curing pickle, which is usually a milder pickle than that employed in
the regular cure, or an even milder pumping pickle might be used. If
mild-cure hams were pumped in this way, the percentage of souring in
these hams could undoubtedly be greatly diminished without materially
affecting the flavor of the ham.
To recapitulate briefly, the prevention of ham souring is to be sought
in two ways: (1) Through greater care in handling the hams and the
adoption of precautionary measures to prevent the introduction of the
ham-souring bacillus into the bodies of the hams, and (2) through more
thorough pumping of the deeper or inner portions of the hams, so as to
create an unfavorable soil or medium in which the ham-souring bacillus
can not develop even if it should gain entrance into the bodies of the
hams.
From what has been said it will be apparent that ham souring can
probably never be entirely eliminated from the packing house under the
present methods of curing, but the adoption of precautionary measures
in testing and pumping hams, together with a more thorough pumping
of all hams in ways similar to those suggested, would unquestionably
reduce very materially the losses from this source.