Structural weakening of skeletal muscle tissue during post-mortem ageing of meat: the non-enzymatic mechanism of meat tenderization.

Structural weakening of the myofibrils, the intermediate filaments and the intramuscular connective tissues the endomysium and perimysium contribute to tenderization of meat during post-mortem ageing. We have found four phenomena which effect the structural weakening of myofibrils: weakening of Z-disks, weakening of rigor linkages formed between actin and myosin, splitting of connectin (titin) filaments, and fragmentation of nebulin filaments. These reactions are specific to 0.1 mM calcium ions regardless of proteolysis. Desmin molecules which form intermediate filaments are also fragmented by 0.1 mM calcium ions nonenzymatically. The fragmentation of desmin molecules suggest depolymerization of intermediate filaments under non-physiological conditions. These facts are the basis of 'the calcium theory of meat tenderization' which I have proposed. The structural weakening of the endomysium and perimysium shows the effect on tenderization of extended ageing of meat, and is closely related to degradation of proteoglycans which link collagen fibrils and stabilize collagen fibres.