EFFECTS OF PHYSICAL AND MECHANICAL TREATMENTS ON THE TENDERNESS OF THE BEEF LONGISSIMUS

SUMMARY— 280 steaks from 56 beef carcasses were evaluated to determine the effects of different mechanical and physical methods for increasing the tenderness of the longissimus muscle. Changes in method of suspension, carcass integrity or chilling procedures resulted in increases in tenderness of approximately 47.5% for shear force and 53.6% for taste panel ratings. Experiment 2 (suspension from the achilles tendon, severance between vertebrae in 5 locations, severance of the ligamentum nuchae and the attachment of 68 kg weights) resulted in a 15% increase in tenderness as evaluated by both shear force values and the taste panel ratings. Experiment 3 (suspension via the obturator foramen, severance of the vertebrae in 5 different locations, severance of the ligamentum nuchae and the attachment of 68 kg weights to the neck) gave the greatest positive response in taste panel tenderness ratings (53.6%). Experiments 3, 4, 5 and 6 had the disadvantage of resulting in irregularly shaped carcasses, which could present problems in fabrication. The assumption that increases in carcass length are necessary to achieve o positive response in the tenderness of the longissimus appears unjustified, since post-mortem chilling at elevated temperatures (16°C) increased tenderness 47% with no appreciable change in carcass length. It was concluded from this study that the degree of post-mortem muscle contraction which occurs during the development of rigor mortis is a primary factor influencing the ultimate tenderness of beef. The degree of such contraction is related to the temperature at which the carcass is stored during the initial period of cooling. Chilling the carcass in a 16°C cooler during the first 16 hr post-mortem resulted in a 40.2% increase (P < .05) in ratings of longissimus tenderness and a 47.5% decrease (P < .01) in shear force requirement, yet involved no additional labor expense nor any irregularity in carcass form. Of the methods studied, the procedure involved in experiments 8 and 9 (chilling the carcasses for the first 16–20 hr in a cooler at 16°C) appears to be the most practical for industrial utilization.

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