Comparison of muscle fiber type and chemical composition of Japanese black beef by meat quality grade, sex, and loin site

Abstract

We examined the relationship between meat quality grade, sex of cattle, loin site, muscle fiber type, and chemical composition of Japanese Black beef. A total of 12 beef of meat quality grade 3, 4 and 5, were used. They include two heifers and two steers for each meat quality grade. Approximately 1kg of ribeye and sirloin from the 12 beef were sampled. These were frozen and stored after aging for 2 weeks after slaughter. The proportions of type I and type II muscle fibers, crude fat content, fatty acids, sugar components, Nucleic acid-related substances, free amino acids, and peptides were measured. With increasing meat quality grade, content of crude fat and oleic acid increased, and sugar components, inosinic acid, and Nucleic acid-related substances, and the content of many amino acids decreased significantly. There was no significant sex difference in muscle fiber type and chemical composition, and sirloin had a significantly higher proportion of oleic acid and monounsaturated fatty acids than ribeye. The percentage of type I muscle fibers showed a significant correlation of 0.50 with shear force value and 0.61 with glutamine. Our findings suggested that glucose, inosinic acid and Nucleic acid-related substances, and many amino acids decreased significantly as the crude fat content increased.