Calpain-1 activity in bovine muscle is primarily influenced by temperature, not pH decline

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2014-03-01
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Mohrhauser, D.
Underwood, K.
Weaver, A.
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Lonergan, Steven
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Animal Science

The Department of Animal Science originally concerned itself with teaching the selection, breeding, feeding and care of livestock. Today it continues this study of the symbiotic relationship between animals and humans, with practical focuses on agribusiness, science, and animal management.

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The Department of Animal Husbandry was established in 1898. The name of the department was changed to the Department of Animal Science in 1962. The Department of Poultry Science was merged into the department in 1971.

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The objectives of this study were to 1) determine the conditions (temperature and pH) that exist in early postmortem muscle of normally chilled and delay chilled beef carcasses to provide a model for in vitro work and 2) determine the mechanism by which early postmortem temperature/pH conditions found in beef muscle influence the enzymes that regulate the aging process in vitro. For objective 1, 7 finished beef animals (HCW 385 ± 8 kg) were harvested with the right sides subjected to normal chilling (2.3°C) approximately 1.25 h postmortem and the left sides subjected to ambient temperature (delay chilling; 22.6°C) for an additional 4.75 h postmortem and then allowed to chill at 2.3°C. Delay chilled carcasses had a more rapid pH decline (P < 0.05) and a slower rate of carcass cooling (P < 0.05). No differences were observed between normally chilled and delay chilled samples for sarcomere length or postmortem proteolysis of troponin T (TnT; P > 0.10). Warner-Bratzler shear force (WBSF) was reduced in steaks from normally chilled carcasses at 14 d (P < 0.05), while results indicated a strong, positive correlation between 14-d WBSF and 3-h longissimus dorsi muscle (LM) temperature (r = 0.67, P < 0.01) as well as a strong, negative correlation between 14-d WBSF and 6-h LM pH (r = –0.65, P < 0.02). These results were used to design the methodology for objective 2, where isolated myofibrils were subjected to μ-calpain digestion at 4 or 22°C with either a fast or slow initial pH decline. As expected, digestions with a fast initial pH decline had lower pH values in the early time points of the incubation (P < 0.05). No differences were detected in μ-calpain activity or in the degradation of intact TnT between the fast and slow pH decline treatments (P > 0.10); however, warmer digestions resulted in a tendency for increased activation of μ-calpain (P < 0.10) and a significant reduction in intact TnT (P < 0.05). Additionally, a temperature × time interaction was revealed in μ-calpain activity and in the degradation of intact TnT (P < 0.05). Specifically, assayed calpain activity was lower at 0.17, 0.33, 1, and 3 h and greater at 72 h in warmer digestions, while intact TnT disappearance was greater as both time and digestion temperature increased. Meat aging and μ-calpain activity are influenced by both temperature and pH, but more research is necessary to fully realize their relationships.

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This article is from Journal of Animal Science 92 (2014): 1261–1270, doi:10.2527/jas.2013-7270. Posted with permission.

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Wed Jan 01 00:00:00 UTC 2014
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