REPEATABILITY OF TENDERNESS MEASUREMENTS IN BEEF ROUND MUSCLES

The present experiment was conducted to determine 1) the repeatability of Warner-Bratzler shear force and trained sensory panel tenderness r atings in beef round cuts and 2) the effect of location within beef ro und cuts on shear force and tenderness ratings. Biceps femoris (BF) an d semitendinosus (ST) were obtained from the carcasses of youthful (A- maturity), grain-fed, crossbred steers (n = 25) at 16 d postmortem. St eaks were removed from each muscle for determination of shear force an d tenderness rating at each of three locations (A = proximal end, B = center, and C = distal end). Tenderness ratings of triplicate samples were slightly more repeatable than shear force for BF (R = .50 vs .30) and ST (R = .60 vs .56). However, all of those estimates of repeatabi lity were much less than values we have obtained for beef longissimus using similar laboratory procedures (R = .79 to .90). Across both musc les and both methods of assessing tenderness, less than 40% of the tot al variance was accounted for by animal. The variance of tenderness ra ting among animals was less for BF (.12) and ST (.09) than values we h ave obtained for beef longissimus (.60). Location did not affect (P > .05) BF shear force; however, BF tenderness ratings were higher(P < .0 5) for location A (5.5) than for B (5.0) and C (5.2). Location account ed for a higher percentage of the total variance of ST tenderness rati ng and ST shear force than did animal. Shear force decreased (P < .05) from the proximal end to the distal end of ST (5.1, 4.6, and 3.9 kg f or locations A, B, and C, respectively). Also, ST tenderness ratings w ere lower for location A (4.8) than for locations B (5.6) and C (5.7). Neither method of measuring tenderness was highly repeatable for BF o r ST because there was little animal-to-animal variation in tenderness for these round muscles. Thus, there would be little opportunity for segregating round muscles into tenderness classes.