Effect of electrical stimulation on protease activity and tenderness of M-longissimus from cattle with different proportions of Bos indicus content

The effect of electrical stimulation on protease activity (at approx. 3 h p ostmortem), sensory tenderness scores and shear force was determined on M. longissimus samples from three Bos indicus genotypes (0% Hereford, 50% Brah man x Hereford and 100% Brahman). The samples were divided and aged for 1 o r 30 days. Electrical stimulation resulted in a general reduction in calpas tatin activity suggesting that it accelerated proteolysis. Calpastatin acti vity increased commensurate with increasing Bos indicus content. Several si gnificant interactions were shown, the most relevant of these was the inter action between Bos indicus content x electrical stimulation. In contrast to the other genotypes, calpain I and calpain II activities were shown to inc rease (significant for calpain II only) following stimulation in the purebr ed Brahmans (100%). There was a significant reduction in tenderness with in creasing Bos indicus content. However, breed differences in shear force wer e reduced by electrical stimulation. The improvement in shear force followi ng ageing was smaller for stimulated carcasses compared to the controls. Th is tends to reinforce the premise that electrical stimulation accelerates p roteolysis. The results of this study show clear genotypic differences in p roteolytic activity and tenderness. However, electrical stimulation can be employed to reduce breed differences in tenderness of the M. longissimus. ( C) 2000 Elsevier Science Ltd. All rights reserved.