PREDICTORS OF BEEF TENDERNESS AMONG CARCASSES PRODUCED UNDER COMMERCIAL CONDITIONS

Beef carcasses (n = 240), processed using conventional commercial proc edures and selected to differ in weight and s.c. fat thickness, were u sed to evaluate marbling score, s.c. fat thickness, 3-h pH (pH(3)) of the longissimus muscle (LM), and early-postmortem measurements of LM t emperature as predictors of rib steak tenderness. Of the carcass trait s evaluated, marbling score was the best single predictor of shear for ce (WBS) and panel ratings for myofibrillar tenderness (MFT). However, marbling, used alone, accounted for only 9.0 and 5.1% of the variatio n in WBS and MFT, respectively, and was not associated with panel rati ngs for connective tissue amount (CTA). Including pH(3) in the predict ion equation for WBS increased the R(2) to .115, and inclusion of s.c. fat thickness in the equation for MFT increased the R(2) to .062. Rat ings for CTA were most effectively predicted using a regression equati on that included 9-h LM temperature, pH(3), and s.c. fat thickness (R( 2) = .063). Marbling score was the most effective factor evaluated for classifying carcasses into tenderness groups. Use of a minimum fat th ickness constraint of .5 cm was effective for identifying tenderness d ifferences among Select grade carcasses but was less effective within the Choice grade. Compared with marbling and s.c. fat thickness, pH(3) was less effective for use in classifying carcasses into tenderness g roups; however, pH(3) values below 6.2 were associated with a reductio n in tenderness variation. Measurements of early-postmortem LM tempera ture were not effective for use in identifying differences in tenderne ss.