Postmortem proteolysis and tenderization of top loin steaks from Brangus cattle

Variations in calpastatin activity (CA) and postmortem (PM) degradation of myofibrillar protein are hypothesized to be related to variations in PM tenderization of beef. The objective of this study was to define the relationships between CA, calpastatin specific activity (CSPA), PM degradation of myofibrillar protein, and Warner-Brattier shear (WBS) force values in steaks aged 2, 7, and 14 days PM. Brangus bulls (n=43) and steers (n=51) were utilized to define these relationships. Steaks from bulls had higher WBS, and CA, in samples aged 2 and 7 days PM, but not after aging 14 days PM, as compared to steaks from steers. CSPA was correlated with WBS after 7 (r=0.570) and 14 (r=0.424) days PM. Degradation of troponin-T after aging 2 days PM was a consistent indicator of proteolysis and tenderization. WBS, CA, CSPA, and PM degradation of myofibrillar protein after aging 2 days PM may be reliable predictors of rate of tenderization during the aging process.