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 ten derization of beef. The objective of this study was to define the relations hips between CA, calpastatin specific activity (CSPA), PM degradation of my ofibrillar 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 util ized to define these relationships. Steaks from bulls had higher WBS, and C A, in samples aged 2 and 7 days PM, but not after aging 14 days PM, as comp ared 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 w as a consistent indicator of proteolysis and tenderization. WBS, CA, CSPA, and PM degradation of myofibrillar protein after aging 2 days PM may be rel iable predictors of rate of tenderization during the aging process.