Fragmentation of myofibrils, limited proteolysis and water holding capacity of meat

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Abstract
Protein changes in ageing meat result in increased vulnerability of the myofibrils to fragmentation, caused possibly by limited proteolysis. It was investigated which groups of muscle proteases, if any, were involved and what was the relation between fragmentation and hydration of beef meat. In samples ranging in natural pH from 5.4 to 7.0 the least framgmentation after 3 days at 2 °C was at pH 6. This could suggests the role of both the cathepsins and neutral proteases. In samples aged in the presence of EDTA fragmentation was significantly lower than in the controls. This could indicate the role of Ca2+ activated neutral proteases, or support the hypothesis on the nonezymatic mechanism involving Ca2+. The results of PAG electrophoresis could not have been dur to the neutral proteases, as the 30000 g. mol−1 component, resulting from the hydrolysis of troponin. T, did not accumulate at pH 7 until the 9the day of ageing, but at pH 5.4 the intensity of this band increased markedly already after 3 days. There was no correlation between the fragmentation and the hydration of the aged meat after cooking. The addition of 0.001% of trypsin or 0.0005% of papain to minced meat did not cause after 9 days any increase in the contents of free amino acids and peptides or significant changes in the PAGE pattern as compared to those in the controls. However, the fragmentation and hydration of the raw meat was larger in the samples containing added enzymes. After cooking the hydration of the samples did not differ. This means that the influence of cooking is more important than that of the enzymatic changes in the proteins.