Abstract
The present study was conducted to elucidate the changes in the calpain activity, protein profile, and physicochemical properties of cold‐boned muscles from culled dairy cows during aging. Semimembranosus and Biceps femoris were used as the study model and were vacuum packaged and stored for 14 days at 4 ± 1°C. The samples were analyzed for pH, shear force, myofibrillar fragmentation index (MFI), calpain activity, and myofibrillar protein profile (1D‐SDS‐PAGE). A significant (p < 0.05) effect of aging was observed on the pH, shear force, and MFI of both the muscles. Casein zymography results indicated the presence of intact and autolyzed forms of calpain 1 and calpain 2. An increase in autolysis of the calpains and proteolysis was observed in both the muscles during aging. Aging for two weeks was effective (p < 0.05) in reducing the shear force of both the muscles by 30%; however, the aged muscles were still excessively tough.
Practical applications
Information is seldom available in the literature about the effect of aging on the calpain activity of the muscles from older animals, such as culled dairy cows, and the subsequent tenderization of such muscles during aging. An analysis of the changes in the proteins and activity of calpains during aging gives us an understanding of the biological basis of the changes in the tenderness of muscles. Tenderness of beef is considerably determined by the activity of the calpains and the changes in the myofibrillar proteins during aging. The results of the present study should be useful to the meat industry for predicting the beef quality, particularly the tenderness of the muscles from culled dairy animals during the aging process. Aging alone was not effective in tenderizing the muscles and other tenderization interventions are required in conjunction with aging, such as nonthermal technologies, to reduce the extra toughness associated with the muscles of culled dairy animals.