Electron Microscopy of Post-Mortem Changes in Porcine Muscle

The mechanism for the promotion of tenderness in meat during the post-mortem process: a review

The post-mortem changes in the chemical composition and structure of striated muscle have been reviewed on the basis of various concepts that emerged from the studies of different investigators to explain the course of tenderization of meat during aging. These concepts include the changes in the sarcoplasmic proteins, myofibrillar proteins (such as complete dissociation of actomyosin, partial dissociation of actomyosin, cleavage of disulfide linkages, depolymerization of F-actin filaments, cleavage of myosin filaments, disorganization of Z-bands and the troponin-tropomyosin complex), sarcolemma, connective tissue elements (collagen fibrils, ground substance), and the protein-ion relationship of the muscle cells (more strictly, syncytia). The experimental evidence for and against each of the views is discussed critically in the light of certain fundamentals of biophysical chemistry and biochemistry. Finally, an alternative hypothesis has been presented based on the differential effect of the post-mortem formation of lactic acid (H+ ion concentration) on the intra- and extracellular components of muscle and the possible role of lysosomal cathepsins. Consequently, a series of biophysical, biochemical, and ultrastructural changes seem to account for the mechanism by which meat becomes tender during the aging process.