A proposed mechanism of tenderising post-rigor beef using high pressure-heat treatment.

Tenderness of beef M. Sternomandibularis was tough when cooked from both raw, and when previously heated (60 degrees C, 20 min), whereas a significant improvement in tenderness was achieved when pressure-heat (P-H) treated muscle (200 MPa, 60 degrees C, 20 min) was cooked. In order to determine the mechanism for this improvement, connective tissue, myofibrillar and sarcoplasmic proteins, were separated into three fractions and studied with regard to their solubilisation, denaturation and aggregation, degradation and strengthening of protein structures for the three treatments (raw, heated and H-P treated). Measurements included DSC, SDS-PAGE, surface hydrophobicity, and the appearance, length and width of myofibres (light microscopy). For the connective tissue fraction, heat solubility was determined. It is suggested that the mechanism for this improvement in tenderness is the formation of a strengthened myofibrillar structure that, when sheared by mastication, allows the crack to pass through the meat rather than dissipate into a more visco-elastic structure. In this way a more brittle fracture is achieved and the meat is perceived as more tender. The pre-requisite is that adequate enzymatic activity has occurred. It is suggested that cathepsins are responsible.