Pressure-heat treatment of meat: Changes in myofibrillar proteins and ultrastructure

The effects on muscle of a combined pressure-heat (P-H) treatment that overcomes myofibrillar toughness have been investigated using SDS gel electrophoresis and electron microscopy. Densitometer scans of polyacrylamide gels of muscle extracts revealed that P-H treatment caused greater degradation of connectin than did heat treatment alone. Breakdown of connection by P-H treatment was reduced in muscle that had been injected with the protease inhibitor pepstatin. However, pepstatin treatment did not reduce the effectiveness of P-H treatment for tenderizing meat, as would be expected if connectin was responsible for myofibrillar toughness. P-H treatment resulted in an increase in the intensity of a peak with M(r) ∼ 150 000, but this peak was also produced by non-tenderizing pressure treatments. The ultrastructural studies revealed that P-H treatment disrupted the thick and the thin filaments, leaving voids at the M-line region. It is suggested that P-H treatment achieves most of its effect by an irreversible disaggregation of the myosin of thick filaments.