Differences in Cathepsin B + L and Calcium-Dependent Protease Activities Among Breed Type and Their Relationship to Beef Tenderness

Activities of acidic proteases (cathepsin B + L) and neutral, calcium-dependent proteases (CDP) were quantified to determine whether differences in proteolytic activity could explain differences in meat tenderness among breed types. Steers (n = 32) of known percentage Angus (A) and Brahman (B) breeding were used to establish differences in meat tendemess (A; 3/4A-1/4B; 1/2A-1/2B; 1/4A-3/4B). Samples were removed from the longissimus muscle within 1 h postmortem and within 2 h were frozen for subsequent determination of cathepsin B + L, CDP-I, CDP-II and CDP-inhibitor activities. Warner- Bratzler shear (WBS) was assessed after 1, 5 and 10 d of postmortem aging. Taste panel evaluations, conducted on steaks that were subjected to 5 d of aging, detected no differences. At d 1, WBS did not differ among breed types; however, by d 10 of aging, steaks from Angus steers were more tender (P \u3c .05) than steaks from 1/2B and 3/4B steers. The Angus and 114B steaks had significantly more (P \u3c .05) cathepsin B + L activity than the 3/4B. The CDP had no relationship with WBS; however, CDP-inhibitor was positively related to d-1 WBS (r = .41, P \u3c .05). Cathepsin B + L activity was negatively related to WBS at d 10 (r = -4, P \u3c .05). These data suggest that differences in meat tenderness among breed types may be explained partially by differences in proteolytic enzyme activity