Identification of factors associated with variability in tenderness among beef carcasses of the same U.S.D.A. grade

Vita.Eighty bovine carcasses were selected from among 1005 carcasses of known grade and tenderness (sensory panel ratings and shear force values). Five grade-maturity groups (U.S. Choice, A maturity, n=20; U.S. Choice, B maturity, n=10; U.S. Good, A maturity, n=20; U.S. Good, B maturity; n=10; U.S. Commercial, C maturity, n=20) were characterized with regard to the relative tenderness of their cooked loin steaks according to variation in traits related to actomyosin effects, background effects and bulk density-lubrication effects, background effects and bulk density-lubrication effects. It should be emphasized that carcass scores of physical, chemical and histological measurements were determined from a population of carcasses (n=80) selected specifically to provide the greatest possible range in cooked meat tenderness. As such, the magnitude and direction of correlations is biased to the extent that the variability in tenderness in this set of data is discrete and clustered (there are two to four tenderness clusters per population subsample-grade, maturity group, et cetera) rather than continuous and normally distributed. Among U.S. Choice, A maturity carcasses, carcasses providing the most tender loin steaks had higher (P<.05) levels of intramuscular fat content (Actual, WTB or MFB), lower intramuscular moisture content, higher water holding capacity, higher fragmentation filtrate volume and lower fragmentation values for Fractions 1, 1+2+3, and 1+2+3+4 of longissimus muscles. Among U.S. Good, A maturity carcasses, carcasses providing the most tender loin steaks and higher (P<.05) levels of filtrate volume, lower values for Fractions 1, 3, 1+2+3, 1+2+3+4 and higher values for Fraction 4 from fragmentation analyses of longissimus muscles.