The sour hams examined were obtained from four different packing
establishments. All of the hams studied were “sweet-pickle hams” which
had not been smoked. The sour hams selected for examination were good
typical body sours, in which the sour odor was well developed, but not
of the very pronounced or putrefactive type.
The sour odor in every case was found to be more pronounced next to
the bone, being usually rather more pronounced just behind the bone,
that is, on the fat side of the bone. The sour odor in each instance
was confined to an area of meat immediately surrounding the femur and
extending out through the body of the ham for a variable distance, as
shown by the dotted lines in figure 1, but in no case did the sour odor
extend all the way to the margin of the meat, nor did it as a rule
extend below the tibio-femoral articulation, the shank proper and the
bone marrow of the shank (i. e., of the tibia) being usually sweet. The
butt portion of the hams—that portion above and behind the hitch bone
(symphasis pubis)—was also sweet.
Immediately after sectioning, the sour areas, as a rule, could be
readily distinguished by a difference in color. In the freshly cut
hams the muscular tissue near the bone, where the sour odor was more
pronounced, exhibited a slight but distinct grayish hue, at times
having a slight greenish tinge; in other words, the muscular tissue in
the sour areas lacked the normal bright red color of the sound meat
and was distinctly lighter in color than the surrounding tissues.
Upon exposure to air, however, the lighter, grayish, sour areas tend
to assume a reddish hue and become much less pronounced than in the
freshly cut ham. After the cut surface of the ham has been exposed to
the air for some time it may be difficult to distinguish the sour areas
by any difference in color.
[Illustration:
BUL. 132, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE.
PLATE I.
FIG. 1.—SECTION OF MUSCULAR TISSUE FROM SOUND HAM, SHOWING
MUSCLE FIBERS CUT LONGITUDINALLY; NUCLEI SHARPLY DEFINED AND
CROSS STRIATION DISTINCT.
(Pen-and-ink drawing made with camera lucida from section stained with
hematoxylin and eosin to show histological structure. × 320.)]
FIG. 2.—SECTION OF MUSCULAR TISSUE FROM SOUR HAM, SHOWING
MUSCLE FIBERS CUT LONGITUDINALLY; NUCLEI UNDERGOING
DISINTEGRATION AND CROSS STRIATION INDISTINCT.
(Pen-and-ink drawing made with camera lucida from section stained with
hematoxylin and eosin to show histological structure. × 320.)]
[Illustration:
BUL. 132, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE.
PLATE II.
FIG. 1.—SECTION THROUGH MUSCULAR TISSUE OF HAM WHICH HAS
UNDERGONE NATURAL OR SPONTANEOUS SOURING, SHOWING DISTRIBUTION
OF BACILLI BETWEEN THE MUSCLE FIBERS, WHICH ARE CUT OBLIQUELY.
THE DARK MASSES BETWEEN THE MUSCLE FIBERS REPRESENT CLUMPS OF
BACILLI.
(Pen-and-ink drawing made with camera lucida from section stained by
the Gram-Weigert method to show bacteria. × 85.)
FIG. 2.—SECTION THROUGH MUSCULAR TISSUE OF HAM WHICH HAS
UNDERGONE NATURAL OR SPONTANEOUS SOURING, SHOWING INDIVIDUAL
BACILLI BETWEEN THE MUSCLE FIBERS, WHICH ARE CUT SOMEWHAT
OBLIQUELY. NUCLEI HAVE LOST SHARP OUTLINE AND CROSS STRIATION
IS INDISTINCT.
(Pen-and-ink drawing made with camera lucida from section stained by the
Gram-Weigert method to show bacteria. × 320.)]
In the sour areas near the bone the muscular tissue was distinctly
softer; that is, it broke and cut more readily than the surrounding
tissues. This was usually quite noticeable in cutting out plugs of the
meat for making cultures. In a ham which shows pronounced souring the
muscular tissues in the worst affected areas may become quite soft and
even slightly gelatinous.
The sour areas, when tested with litmus paper, frequently showed a
slight but distinct alkaline reaction. When aqueous extracts of the
sour meat, however, were titrated with phenolphthalein they were found
to be acid.