Effects of zilpaterol hydrochloride feeding duration on crossbred beef semimembranosus steak color in aerobic or modified atmosphere packaging.

The objective of this research was to determine the effects of feeding zilpaterol hydrochloride (ZH) for 0, 20, 30, or 40 d before slaughter (ZH0, ZH20, ZH30, or ZH40, respectively) on semimembranosus (SM) color development and stability. A 7.62-cm-thick portion was removed from 60 beef steer SM subprimals and stored (2 degrees C) for 21 d; then two 2.54-cm-thick steaks were cut, overwrapped with polyvinyl chloride (PVC) film, and assigned to 0 or 3 d of display. Remaining portions of the subprimals were stored in a vacuum for 10 d and then enhanced 10% to a meat concentration of 0.3% sodium chloride, 0.35% phosphate, and 0.05% rosemary extract. Steaks were packaged in a high-oxygen (HO-MAP) or carbon monoxide (CO-MAP) modified atmosphere and assigned to 0, 3, or 5 d (HO-MAP) or 0 or 9 d (CO-MAP) of display. The deep (DSM) and superficial (SSM) portions of steaks were evaluated for initial color, display color, discoloration, pH, L*, a*, b*, hue angle, and saturation indices. For steaks in PVC, no differences (P > 0.05) occurred in initial or discoloration color scores because of ZH feeding duration. The enhanced SSM steaks from ZH20 in PVC were brighter red (P < 0.05) than SSM steaks from ZH40 in PVC. The DSM in PVC had less (P < 0.05) pH and paler (P < 0.05) color than the SSM. Display color scores for the DSM of PVC steaks were brighter red (P < 0.05) than the SSM initially (d 0 and 1), but the DSM discolored faster (P < 0.05) than the SSM on d 1 to 3. The SM steaks from steers fed ZH20 or ZH30 were slightly brighter and less discolored during display in PVC than the ZH40 diet. For enhanced steaks in HO-MAP, the DSM of ZH20 and ZH30 diets displayed 4 d and the DSM of ZH20 displayed 5 d was a brighter (P < 0.05) red than the DSM from ZH40. At display d 1 and 5, the SSM of ZH20 steaks in HO-MAP was a brighter (P < 0.05) red than SSM steaks from ZH40. The SSM of ZH40 HO-MAP steaks was darker (P < 0.05) red on d 3 than the SSM from other diets. For enhanced steaks in CO-MAP, ZH30 steaks were brighter (P < 0.05) red than ZH0 or ZH40 steaks on d 0 and 9 of display. Steaks in CO-MAP from all feeding durations were less than 20% discolored through d 9. The DSM was lighter (P < 0.05) than the SSM on d 0 for steaks packaged in HO-MAP and CO-MAP. Feeding cattle ZH for 20 or 30 d will yield steaks with color characteristics equal to or better than steaks from control cattle, whereas feeding ZH for 40 d will likely produce less desirable meat color traits.