Effects of Chilling Duration on Marbling Score of Beef Carcasses

Abstract

Two hundred and nine beef carcasses (body weight of 361 ± 53 kg) from crossbred, grain-finished cattle were harvested in a commercial abattoir and subjected to continuous chilling for 96 h at 0°C to 3°C in a commercial hot box with a wind speed of 3.1 m/s and 153 lux of fluorescent light. At 24, 48, 72, and 96 h, the carcasses were analyzed for fatty acid composition, marbling score, pH, shrinkage, color, and aerobic plate count (n = 50). Carcasses reached 3°C after 12 to 16 h of chilling. There were minimal changes in shrinkage among time point (−0.4% to 1.2%; P ≤ 0.002), pH (5.56 to 5.69; P ≤ 0.001), and aerobic plate count (0.1 to 0.7 log; P <0.001). Initial 24-h grading by a USDA grader revealed a grade composition of 21.1% Slight (n = 44), 34.0% Small (n = 71), 17.2% Modest (n = 37), 17.7% Moderate (n = 36), and 10.1% Slightly Abundant (n = 21). With a marbling score in numeric values between 200 (Practically Devoid00) and 1100 (Abundant00), carcasses that had Small or greater marbling score at 24 h experienced a decrease of 34 to 60 points after 96 h of chilling (P ≤ 0.042). Comparatively, the marbling scores of the Slight carcasses increased from 442 points at 24 h to 469 points at 96 h. Moreover, Slight carcasses had a greater percentage of polyunsaturated fatty acids (P <0.001). Results indicate that chilling for 96 h increases the marbling score of USDA Select but has minimal impacts on the marbling score of greater USDA quality grades.