EARLY POSTMORTEM MUSCLE SHORTENING AND TENSION IN RELATION TO TENDERNESS IN BEEF M. LONGISSIMUS

The purpose of this study was to investigate muscle tension and shortening in relation to tenderness in beef M. longissimus. Initially, an intercalibration of six identical rigormeters using a polyacrylamide standard showed that the rigormeters gave reproducible results. This means that the rigormeter is a potentially valuable tool in studies of postmortem muscle tension and shortening. Tension and shortening of M. longissimus from 24 bulls carcasses exposed to two different chilling regimes were measured 1.5 to 20 h postmortem in the rigormeters. The muscle samples were separated into three groups; fast chilled (all tough), slow chilled (tough) and slow chilled (tender). On average, both the developed tension and accumulated shortening of muscle strips during this period were highest in tender, slow chilled samples and lowest in fast chilled samples. There was a relationship between glycolytic rate and the muscle contraction process, as the fast glycolyzing muscles exerted the fastest development of tension and contraction. This study indicates that tension and, shortening, as measured in the rigormeter, is related to WB shear force measured in aged meat.