Biochemistry of Pork Muscle Structure. II. Preliminary Observations of Biopsy Samples versus Ultimate Muscle Structure ^a

Abstract

SUMMARY Preliminary observations were made on biopsy and post‐mortem samples from six Danish Landrace barrows. Additional studies were also conducted on post‐mortem muscle samples from 30 Danish Landrace pigs of known breeding and nutrition. The biochemical characteristics studied were related to the continuous post‐mortem measurements of pH and temperature, which were used to predict muscle structure. These data imply that the biopsy samples from pigs that ultimately showed the severe depression and elevation in pH pattern, contained greater total glycogen, lower percentage of acid‐soluble glycogen, and faster phosphorylase activity. Similarly, these pigs possessed a smaller pyruvic acid pool and a greater lactic acid concentration. Results from measurements of methylene blue reduction, in the presence of lactate, suggest that the methylene blue is reduced much more slowly in muscles from pigs with the type 4 pH pattern. Although this criterion was significantly correlated with zinc concentration, ultimate color intensity, and water‐binding capacity, special emphasis was placed on the severe limitations that must be imposed on interpretation of this measurement. The significant correlations collectively suggest, however, that if the samples showed a rapid reduction of methylene blue, they were ultimately uniform in color, dry in appearance, and firm in structure. Significant additional correlations were shown for numerous biochemical characteristics of pork muscle tissue.

Influence of pH and temperature on properties of myosin A in glycerol-treated fiber bundles

“…Although the rate of thermal denaturation of myosin A in the glycerol-treated fiber bundles was considerably slower than that observed in the isolated myosin , it seemed to be more sensitive to temperature than to pH (Figures 5-8). It is a well-known fact that pale watery meat occurs when the rate of postmortem pH fall is three or more times higher than the normal rate and the muscle is not allowed to cool below 38°before the pH falls below 6.0 (Briskey and Wismer-Pedersen, 1961; Wismer-Pedersen, 1959). The results mentioned above will give an important clue in explaining the change in the quality of pale watery meat.…”

The influence of pH and temperature on the properties of myosin

“…In normal muscle, with an initially high glycogen content, the pH falls from about pH 7-0 to about pH5-4, during the course of rigor, but the rate of fall is usually so low that the muscles on a carcase will have cooled well below body temperature (38°) before the ultimate value is attained. In certain cases, however, particularly in pig muscle, the rate of glycolysis and of pH fall can often be three or more times the normal rate, and the muscle will not have had time to cool below 380 before the pH has fallen below 6-0 (Ludvigsen, 1954;Wismer-Pedersen, 1959;Briskey & Wismer-Pedersen, 1961). Such conditions give rise to considerable protein denaturation and the occurrence of socalled 'white' or 'watery' meat, which may exude more than 10% of its weight as drip.…”

Biochemical Aspects of Post-Mortem Changes in Porcine Muscle

“…Association of Sarcomere Length with Dark Fiber Content. Normally dark or highly pigmented muscles (9) have a slow rate of glycolysis (13) and are subsequently more resistant to the development of the PSE condition (8).…”