Effects of postmortem calcium chloride injection on meat quality traits of steaks from cattle fed with zilpaterol hydrochloride

Two experiments were conducted to determine the effects of zilpaterol hydrochloride supplementation (ZH; 6.8 g/ton on a 90% DM basis for 20 d) and calcium chloride injection (CaCl2 200 mM at 5% wt/wt into 72 h postmortem) on palatability traits (Exp. 1) and shelf-life (Exp. 2) of beef strip loin steaks. Select (USDA) strip loins were obtained from control (non-ZH-fed) and ZH-fed cattle carcasses (Exp. 1= 39; Exp. 2= 20) and right and left sides were selected alternatively to serve as a control (non-injected) or CaCl2-injected and immediately vacuum packaged and stored at 4 °C. Before injecting the subprimals (at 72 h postmortem), two initial steak were cut for proximate, sarcomere length and myofibrillar fragmentation index (MFI) analysis, and stored at -20 °C (for proximate) and -84 °C (for sarcomere length and MFI). For Exp. 1, at 7 d postmortem each strip loin was portioned into steaks, vacuum packaged and aged until 28 d for Warner-Bratzler shear force values (WBSF; 7, 14, 21, and 28 d) and trained sensory analysis (14 and 21 d), purge loss (at 7d) and myofibrillar fragmentation index (MFI; at 3, 7, 28 d). For Exp. 2, treatments were evaluated at 7, 14, and 21 d postmortem using color analysis (trained panelist and Hunter colorimeter), pH, steak purge loss, metmyoglobin reducing activity (MRA) and lipid oxidation (TBARS) on steaks which were PVC-overwrapped and placed in retail cabinets for three days at 3 °C. Results from Exp. 1 indicate both feeding groups and injection treatments diminished their WBSF values as days of postmortem aging were increased; however, WBSF values of ZH-fed steaks were greater (P < 0.05) than non-ZH-fed steaks during all postmortem aging periods. The CaCl2-injected steaks showed lower WBSF values (P < 0.05) than non-injected steaks. Furthermore, trained panelist gave a lower tenderness score to ZH-fed steaks than none-ZH-fed steaks at 14 d and 21 d; contrary, the injection of CaCl2 improved (P < 0.05) tenderness ratings and flavor intensity, compared with their non-injected cohorts at 21 d. Non-ZH-fed steaks and CaCl2-injected presented higher MFI values (P < 0.05) with respect to their controls steaks indicating a higher postmortem proteolysis activity. Sub-primals from ZH-fed and CaCl2-injected showed higher purge loss (P < 0.05). Results from Exp. 2 indicate ZH-fed steaks showed better initial color (lighter; P = 0.04) and color stability during retail display than non-ZH-fed (P = 0.02); though there were no differences in discoloration over aging (P = 0.06). Similarly, injected steaks were lighter on initial color score than non-injected steaks (P = 0.005). Nonetheless, at 14 d of aging, injected steaks started to be more discolored and less color stability (P = 0.0001) than those non-injected steaks. These results were in accordance with the instrumental color results. On MRA values, feeding groups were not different (P = 0.2); but injection treatments groups diminished their MRA percentage at 21 d postmortem aging, but injected steak with CaCl2 showed better reducing ability than non-injected steaks. Regard of initial pH values and steaks purge loss, there was not any difference between feeding groups; while CaCl2-injected steaks became acid; but was not affected steak purge loss between injection treatments (P < 0.05). Respect to TBARS values, non-ZH-fed and CaCl2-injected steaks increased lipid oxidation compared to counterpart steaks (P = 0.05). Overall, the postmortem injection of CaCl2 solution to either ZH-fed or non-ZH subprimals can improve beef steak tenderness; however, it can be detrimental to shelf-life when aging is extended beyond 14 d.