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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2007-0741v1 86/8/1925    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Weaver, A. D. Articles by Gerrard, D. E. Search for Related Content PubMed PubMed Citation Articles by Weaver, A. D. Articles by Gerrard, D. E.

Sarcomere length influences postmortem proteolysis of excised bovine semitendinosus muscle

A. D. Weaver^*,1, B. C. Bowker and D. E. Gerrard^*,2

^* Department of Animal Sciences, Purdue University, West Lafayette, IN 47907; and USDA-ARS, Food Safety Laboratory, Beltsville, MD 20705

² Corresponding author: dgerrard{at}purdue.edu

The interaction between sarcomere length and postmortem proteolysis as related to meat tenderness is not clear. The extent of thick and thin filament overlap alters actomyosin binding and may alter substrate availability during aging-induced tenderization. The objective of this study was to determine the influence of sarcomere length on proteolytic degradation in beef. Strips from bovine semitendinosus were either stretched 40% and restrained or allowed to shorten unrestrained in an ice bath. After rigor completion, 0.6-cm cross sections were fabricated and were randomly assigned to 2, 4, 7, or 10 d of aging treatments. Myofibrils were isolated for sarcomere length determination. Samples were collected and frozen for shear force analysis, and muscle proteins were extracted for SDS-PAGE and Western blotting analyses to determine troponin T (TnT) proteolysis. Sarcomere length was greater (P < 0.01) in stretched muscle samples compared with shortened samples (2.57 vs. 1.43 µm, respectively). Correspondingly, shear force values were greater (P < 0.05) in shortened samples than stretched samples. Western blots revealed the presence of 3 major intact TnT bands that diminished with time postmortem and 4 bands (TnT degradation products) that accumulated during postmortem storage. Quantification of intact TnT showed increased (P < 0.05) proteolysis at 4 and 7 d postmortem in samples with long sarcomeres. By 10 d, only traces of the greatest molecular weight intact TnT band were evident in both shortened and stretched samples, suggesting this TnT band may be more susceptible to proteolysis than other intact TnT bands. Degradation products of TnT appeared earlier postmortem in samples with long sarcomeres. The 30-kDa TnT fragment appeared after 7 d of postmortem storage in samples with long sarcomeres but not until 10 d in muscle containing short sarcomeres. Collectively, these data show that postmortem TnT proteolysis is sarcomere length-dependent and suggest that thick and thin filament overlap may influence the postmortem aging process in beef.

Key Words: tenderness • sarcomere length • proteolysis • troponin-T • beef

This article has been cited by other articles:

				A. D. Weaver, B. C. Bowker, and D. E. Gerrard Sarcomere length influences {micro}-calpain-mediated proteolysis of bovine myofibrils J Anim Sci, June 1, 2009; 87(6): 2096 - 2103. [Abstract] [Full Text] [PDF]