The influence of connective tissue content on amino acid composition and rat PER was studied in an attempt to develop a regression equation for predicting PERs of meat from the simple chemical analysis of collagen. Collagen content was highly correlated to essential amino acid content and rat PER with correlation coefficients of -0.99 and -0.98, respectively. The developed regression equation, PER = -0.02290 (collagen content) + 3.1528, effectively predicted rat PER within * 0.2 units when tested on various meat ingredients. These results indicated

Two hundred broilers were commercially processed with and without electrical stunning to determine the effect of stunning on biochemical changes and its relationship to final meat tenderness. Electrically stunned birds were more tender with 30% lower shear values than no-stun controls after 24 hr aging. Breast muscles of electrically stunned birds showed significantly higher ATP, CP and pH, and lower lactate level than no-stun controls during the early processing steps. It was concluded that electrical stunning inhibited the rapid breakdown of ATP, CP and glycogen, and thus delayed the onset of rigor until after spin-chill by which time muscle temperature reached 4°C. Consequently, the rigor process occurred at low temperature where potential heat shortening was avoided, resulting in improved meat tenderness.

The effects of heat stress (38"C), cold stress (4OC) and extreme cold stress (-20°C) before slaughter on the tenderness and postmortem glycolysis of the excised chicken breast muscle were studied. Heat stress significantly (p < 0.05) increased the toughness of breast muscle. Though statistically not significant, cold stress also adversely affected the tenderness. The heat-stressed birds showed higher zero hr glycogen, higher zero hr pH and significantly (p < 0.05) lower ultimate pH than the controls. The cold-stressed birds showed intermediate values in these parameters. Highly significant correlations were observed between shear value and each of these three parameters. Glycolysis rate and final moisture content were minor factors which affected the muscle tenderness to a limited extent. The slightly elevated lactatedehydrogenase and creatine phosphokinase activities in serum and breast muscle of stressed birds failed to account for any variations in tenderness.

Postmortem biochemical changes and their relationship to the eating quality of surf clam muscle were studied. Shear value and cook loss continuously increased with the length of storage time up to 9 days postmortem and the rate of increase was much greater after 4 days of storage. A rapid breakdown of high energy phosphate compounds and muscle glycogen with a concomitant fall in pH after 4 days postmortem suggested that rigor onset occurred at 4 days and was completed between 6 and 9 days postmortem. The biochemical changes in surf clam muscles were much slower than those reported for the muscle systems from other species and were in a close coincidence with the change of shear values and cook loss. Another significant finding was that pyruvate instead of lactate was accumulated as glycolysis proceeded.