RELATIONSHIP OF pH AND TEMPERATURE TO DISRUPTION OF SPECIFIC MUSCLE PROTEINS AND ACTIVITY OF LYSOSOMAL PROTEASES

Abstract

From a review of the literature, and from specific data presented in this paper, it was concluded that both postmortem temperature and pH have effects on meat tenderness and on disruption of specific myofibrillar proteins. Increased postmortem temperature porduces more tender muscles and increases the disruption of troponin-T, myosin, Z-lines, connectin and gap filaments. Elevated postmortem temperature also increases the activity of enzymes which cause the disruption of myofibrillar proteins. Higher ultimate postmortem pH (above 6.0) produces more tender muscle, but also produces dark-cutting meat Except for one experiment, lower pH in the first few hours postmortem (in muscle with normal ultimate pH; i.e., 5.8 or below) improves meat tenderness. High pH increases the activity of CAF and low pH increases the activity of lsosomal cathepsins. Both high and low pH increase the degradation of troponin-T, Z-lines, gap filaments and connectin, but the degradation of these proteins (except for Z-lines) is greater at a low pH. Low pH increases the degradation of myosin; conversely, high pH retards it degradation.