Changes in the Physical and Chemical Properties of Muscles during Conditioning of Japanese Black Cattle

The conditioning of beef (M. semimembranosus) from Japanese Black Cattle was studied by examining changes in the amount of various forms of nitrogen and free amino acids, myofibrillar fragmentation and shear value of muscle during this process at 0°C. The following results were obtained.1. Sarcoplasmic nitrogen in the beef conditioned for 21 and 28 days was significantly (P<0.05) less than in that conditioned for 7 days. Sarcoplasmic protein nitrogen in the beef conditioned for 21 days was significantly (P<0.05) lower than in that conditioned for 7 and 14 days.2. The amount of many kinds of free amino acids significantly changed during conditioning from 7 to 28 days. The amount of Asp after conditioning for 21 days was significantly (P<0.05) lower compared to that after 7 and 14 days of conditioning. Ser decreased on the stage from 21 to 28 days of conditioning (P<0.05). The amounts of Gln and Arg in the beef conditioned for 28 days were significantly (P<0.05) lower than in that conditioned for 14 days. Compared with the beef conditioned for 7 days, Val, Leu and Phe increased in that which was conditioned for 28 days (P<0.05). The mean value of Met increased during conditioning, significant differences (P<0.05) being present among these samples conditioned for 7 days and 21 or 28 days, 14 and 28 days. The changes in the amount of free amino acids in regard to taste were discussed in relation to the improvement of beef taste during conditioning.3. Myofibrillar fragmentation rate in the beef conditioned for 7 and 14 days was significantly (P<0.05) higher than in that conditioned for 21 and 28 days. On the other hand, shear value in the beef conditioned for 7 days was significantly (P<0.05) less than in that conditioned for 21 and 28 days. From these findings, it was evident that beef tenderness was accelerated during conditioning, particularly from 7 to 21 days.