RELATIONSHIP BETWEEN CONTRACTILITY AND SOME BIOCHEMICAL PROPERTIES OF MYOFIBRILS PREPARED FROM NORMAL AND PSE PORCINE MUSCLE

Effect of pre-rigor stretch and various constant temperatures on the rate of post-mortem pH fall, rigor mortis and some quality traits of excised porcine biceps femoris muscle strips

Porcine biceps femoris strips of 10 cm original length were stretched by 50% and fixed within 1 hr post mortem then subjected to temperatures of 4 °, 15 ° or 36 °C until they attained their ultimate pH. Unrestrained control muscle strips, which were left to shorten freely, were similarly treated. Post-mortem metabolism (pH, R-value) and shortening were recorded; thereafter ultimate meat quality traits (pH, lightness, extraction and swelling of myofibrils) were determined. The rate of pH fall at 36 °C, as well as ATP breakdown at 36 and 4 °C, were significantly reduced by pre-rigor stretch. The relationship between R-value and pH indicated cold shortening at 4 °C. Myofibrils isolated from pre-rigor stretched muscle strips kept at 36 °C showed the most severe reduction of hydration capacity, while paleness remained below extreme values. However, pre-rigor stretched myofibrils - when stored at 4 °C - proved to be superior to shortened ones in their extractability and swelling.

Effect of antemortem electrical stunning on functional properties of turkey muscle

Muscle samples were collected from two groups of turkeys, one group electrically stunned before exsanguination and the other group nonstunned. Sampling was done at 0, 4, 8, and 24 h postmortem. Examination of muscle samples for glycogen, pH, adenosine triphosphate (ATP), R value (ratio of inosine nucleotides to adenosine nucleotides), and extractable protein demonstrated that glycolysis was delayed by electrical stunning. Muscle myofibrils, however, showed no effect of stunning on Mg++-ATPase, sulfhydryls, or sodium dodecylsulfate-polyacrylamide gel electrophoresis patterns. Functional properties of the muscle as measured by emulsion stability evaluations showed greater stability in prerigor muscle but no significant effect of stunning. The results indicate that although electrical stunning delayed glycolysis, the overall effect was not great enough to be a significant factor in improvement of functional properties of muscle for further processing.