Effect of rigor temperature on muscle shortening and tenderisation of restrained and unrestrained beef m-longissimus thoracicus et lumborum

Pairs of muscularis longissimus thoracicus et lumborum (LTL) from young bul ls were removed within Ih of slaughter. Small portions of the muscles were placed in a rigormeter to continously follow the isometric tension and isot onic shortening developed, at constant temperatures of 15, 20, 25, 30 and 3 5 degrees C, as the muscle went into rigor. The bulk LTL was placed in wate r baths at the same temperature. One of the bulk pairs was tightly restrain ed by wrapping, to reduce muscle shortening, the other was unrestrained fre e to shorten. For the bulk samples, shear values were measured using a Warn er-Bratzler instrument (1, 7 and 14 days post mortem), and sensory attribut es were measured using a sensory panel (7 and 14 days post mortem). Minimum tension and shortening occurred at 15 degrees C. The activation energy for the muscle shortening process was larger than for the isometric tension pr ocess. This indicates that the isometric tension data, collected during rig or, does not solely reflect muscle shortening. Thus, a counteracting proces s that decreases the tension response, most likely ageing is simultaneously detected. Meat that went into rigor at 15 degrees C had least shortening a nd was always more tender than meat going into rigor at higher temperatures . For meat entering rigor at temperatures higher than 15 degrees C, restrai ning of the muscle by wrapping, significantly (p < 0.05) decreased the amou nt of muscle shortening and resulted in an improved meat tenderness (p < 0. 001). It was also observed that at rigor temperatures higher than 15 degree s C the meat tenderness is affected negatively by a reduced ageing capacity . It therefore appears that muscle shortening and enzyme activity both affe ct tenderness and that both are highly affected by rigor temperature and ha ve the greatest beneficial effect at a rigor temperature of 15 degrees C. ( C) 1998 Elsevier Science Ltd. All rights reserved.