Comparative effects of supplementing beef steers with zilpaterol hydrochloride, ractopamine hydrochloride, or no beta agonist on strip loin composition, raw and cooked color properties, shear force, and consumer assessment of steaks aged for fourteen or twenty-one days postmortem.

Beef steers (n = 1,914) were assigned to 1 of 3 ß-adrenergic agonist (ßAA) supplementation treatments-zilpaterol hydrochloride (ZH; 8.3 mg/kg of DM for 20 d with 3-d withdrawal), ractopamine hydrochloride (RH; 308 mg·head(-1)·d(-1) for 28 d), or no ßAA (CON)-to determine the effects on consumer eating quality. Strip loins (n = 1,101; CON = 400, RH = 355, and ZH = 346) were obtained and fabricated into 2.5-cm-thick steaks for proximate, Warner-Bratzler shear force (WBSF), slice shear force (SSF), and consumer analyses; steaks were aged until 14 or 21 d postmortem. Fat and moisture contents were not affected by ßAA supplementation (P > 0.05), but strip steaks from steers fed ZH had more protein (P < 0.01) than those from steers fed CON or RH, which were similar. An interaction between ßAA and aging was observed (P < 0.01) for WBSF but not SSF. Within steaks aged 14 d, ZH steaks required the most force to shear, RH steaks were intermediate, and CON steaks had the lowest WBSF values; however, RH steaks had a stronger response to aging than CON or ZH steaks, resulting in the lowest WBSF values at 21 d. Slice shear force values were greater (P < 0.01) in steaks from steers fed ZH than in steaks from steers fed CON or RH, which did not differ. Following shear force analyses, steaks within 2 SD of each treatment mean for WBSF were selected randomly for consumer assessment of eating quality. Consumer testing (n = 400; 200/postmortem aging period) was arranged in a 3 × 3 factorial representing 3 quality grades (Select, Low Choice, and Premium Choice) and 3 treatments (ZH, RH, and CON). In steaks aged 14 d, ßAA supplementation affected (P < 0.01) tenderness, flavor, and overall liking and tenderness acceptability, resulting in lower consumer scores for ZH than CON and RH; however, juiciness, flavor, and overall acceptability were similar (P > 0.05). In steaks aged 21 d, feeding ßAA influenced (P < 0.01) only tenderness and juiciness scores. Despite these differences, ßAA did not affect (P > 0.05) acceptability. Quality grade impacted (P < 0.01) all traits and acceptability in steaks aged 14 and 21 d. In 14-d steaks, Premium Choice typically was scored higher than Low Choice or Select; however, consumers rated 21-d Low Choice and Premium Choice similarly-both receiving greater scores than Select. Consumers detected several differences in eating quality at 14 d because of ßAA supplementation. Increasing aging from 14 to 21 d mitigated differences in shear force and tenderness scores because of feeding ZH, so that tenderness and overall acceptability were similar between ZH, RH, and CON.