AN EVALUATION OF CURRENT AND ALTERNATIVE SYSTEMS FOR QUALITY GRADING CARCASSES OF MATURE SLAUGHTER COWS

Strip loins from 354 female bovine carcasses, selected to represent 30 skeletal maturity (A, B, C, D, and E) x marbling score (SA/MA/AB, MD, MT, SM, SL, and TR/PD) subclasses, were used to evaluate current and alternative systems for classifying cow carcasses into expected-palata bility groups. Strip loins were vacuum-packaged, stored for 14 d postm ortem at 2 degrees C, and frozen (-27 degrees C). Five steaks from eac h strip loin, each cooked to a different internal temperature (60, 66, 71, 77, or 82 degrees C), were used for shear force determinations. T wo steaks from each strip loin, one cooked to 66 degrees C and the oth er to 77 degrees C, were used for sensory evaluation. Increased carcas s maturity was associated with decreased tenderness and juiciness, inc reased flavor intensity, and a higher incidence of flavors described a s ''painty,'' ''fishy,'' and ''grassy.'' Position of a carcass within a maturity group had a negligible effect on palatability. Increased ma rbling was associated with greater tenderness and juiciness, a lower i ncidence of steaks with a ''grassy'' flavor, and a higher incidence of steaks with a flavor described as ''fatty.'' Relationships between ma rbling and beef palatability traits were consistent across all maturit y groups. Carcasses of maturities A through E were most effectively st ratified according to differences in palatability when marbling scores were grouped as follows: 1) MD and higher; 2) SL, SM, MT; and 3) TR/P D. Among mature (C, D, and E maturity) carcasses, yellow-colored fat w as associated with greater beef toughness and higher detection rates f or ''grassy'' and ''fishy'' flavors. Higher end-point temperatures wer e associated with higher shear force values and lower ratings for musc le fiber tenderness, connective tissue amount, overall tenderness, and juiciness. Two alternative grading approaches tone involving current quality grading factors and the other involving the use of fat color a s an additional grade factor) were developed for possible use in class ification of cow carcasses into expected-palatability groups. Both alt ernative systems provided a more effective stratification of cow carca sses according to palatability differences than did the current USDA q uality grading system.