Post‐Mortem Changes in Muscle II. Chemical and Physical Changes in Pork

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Abstract
SUMMARY: The chemical changes occurring from 0 to 24 and/or 48 hr post‐mortem were followed in longissimus dorsi muscle from 18 pork carcasses. In an attempt to induce soft, watery pork, one side from each of 13 carcasses was placed at 37°C immediately after slaughter, and the other side of each carcass was subjected to ‐29°C. Values for pH, glycogen, total reducing sugars, and lactic acid differed markedly at 0 time. Carcasses from Poland China pigs showed a stoichiometric relationship between the post‐mortem decrease in glycogen and the corresponding accumulation of lactic acid and total reducing sugars. This relationship was less apparent in Hampshire pigs. The 37°C treatment did not consistently result in soft, watery and pale muscle, as was expected from other reports. This suggests that exposure of muscle to a low pH at a high temperature per se does not necessarily cause the soft, watery, and pale appearance. A loss in fibrillar water‐binding capacity as a result of low pH values and high muscle temperatures confirmed earlier investigations. However, the decrease in fibrillar water‐binding capacity as a result of the low pH at high muscle temperatures did not usually make the muscle appear soft and watery. Results indicate that even though a loss in fibrillar water‐binding capacity occurs as a consequence of a low pH and high temperature, and is a characteristic frequently encountered in soft, watery muscle, low fibrillar water‐binding capacity by itself is not the primary causal factor in making pork muscle appear soft and watery. Post‐mortem levels of ATP, creatine phosphate, lactic acid, total reducing sugars and glycogen are reported and compared with literature values.