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Abstract
This research was conducted to segregate Uruguayan beef carcasses by tenderness under commercial conditions and detect sources of its variation (age, sex, end points, chilling/pH decline rates). Postmortem carcass traits, pH (pH1, pH3, pHu), temperature (T1, T3, Tu) and color (L*, a*, b*) of longissimus muscle were used as predictors of steak tenderness. Two aging times were evaluated: 7 (WBSF7) and 14 (WBSF14) days. In Experiment 1, female carcasses (n=163) were selected at one packing plant (PP). Tenderness differences were explained by dentition (P<0.01). Carcasses with pH3 < 5.8 and a* =20 showed the lowest level of tenderness. WBSF14 showed a high correlation (r) with USDA lean maturity and color values (P<0.01). Lean and overall maturity explained 15 and 23% whereas a* accounted for 32 and 33% of WBSF7 and WBSF14 variation, respectively. A linear regression equation (QG, a*, a*2 , pHu, pHu 2 ) to predict WBSF7 and WBSF14 showed adjusted R 2 =0.34 and 0.38 and an accuracy of 75.6 and 79.5%, respectively, using a WBSF threshold of 4.5 kg. In Experiment 2, male carcasses (n=174) were selected at the same PP. USDA yield grade showed r = -0.22 and -0.22 (P<0.05) with WBSF7 and WBSF14. Lean a* had r = -0.47 and -0.40 with WBSF7 and WBSF14 (P<0.01) and accounted for 22 and 16% of WBSF7 and WBSF14 variation. A linear regression equation (a*, pHu, pHu 2 ) showed an adjusted R 2 = 0.23 and 0.14 and an accuracy of 76.7 and 88.3% for WBSF7 and WBSF14 prediction (WBSF threshold = 3.4 kg). In Experiment 3, male carcasses (n=449) were selected at two PP. There was a significant effect of PP on tenderness (P<0.01). WBSF7 and WBSF14 showed r = 0.43 and 0.44 (P<0.01) with Tu. A linear regression equation (dentition, rib eye area, pHu, Tu, L*, a*, b*) to predict WBSF7 and WBSF14 showed adjusted R 2 =0.25 and 0.26 and an accuracy of 66.1 and 75.6% for both tenderness (WBSF threshold = 4.5 kg). Although QG, pHu and a* measured at ribbing in Uruguayan commercial conditions could contribute to differentiate levels of beef tenderness, other differences between PP could affect segregation effectiveness.