The prediction of fat percentage in the longissimus dorsi muscle in fed beef using nuclear magnetic resonance

The objective of this study was to develop predictive equations to estimate the percentage of crude fat in beef longissimus dorsi muscles from subjective marbling evaluations or objective visual evaluations. Forty beef ribs and loins representing four U.S. Department of Agriculture (USDA) quality grades - USDA Prime (n = 10); USDA Premium Choice [upper 2/3 of Choice] (n = 10); USDA Low Choice (n = 10); and USDA Select (n = 10) - were fabricated into 3.17-cm transverse slices for subjective and objective visual evaluations. Additional 0.63-cm slices were removed for crude fat analysis. Mean crude fat percentages were as follows: USDA Prime = 11.90, USDA Premium Choice = 9.78, USDA Low Choice = 7.08 and USDA Select = 5.29. Regression analysis indicated that crude fat can be estimated with the following equation using a subjective marbling score: = (-0.58) + 0.17 x marbling score (R-2 = 0.55); furthermore, crude fat = (3.47) + 0.73 x objective visual percent fat (R-2 = 0.54).