The Influence of time and temperature at carcass boning on the consumer assessment of eating quality and the objective measures of tenderness of New Zealand beef

A total of 40 carcasses were selected initially to be included in the study. Sides of the 40 carcasses were randomly assigned to either conventional chilling (CB) or hot boning (HB). Five subprimals were removed including the strip loin, cube roll, tenderloin, rump, and topside. Accessory muscles were removed from each subprimal leaving only the longissimus lumborum (LL), longissimus thoracis (LT), psoas major (PM), gluteus medius (GM), and semimembranosus (SM). The HB muscles were removed within 90 minutes of slaughter. The CB sides were chilled for approximately 17-20 hours prior to fabrication. Subprimals were fabricated into 2.5 cm steaks and were appointed to one of three postmortem aging periods (7, 21, or 35 d) for consumer testing and Warner-Bratzler shear force (WBSF) testing. Trim from each individual muscle treatment from each subprimal was also retained for proximate and sarcomere length analyses. Steaks for consumer testing and WBSF were cooked on a Silex clamshell grill (Model S-143K, Silex Grills Australia Pty Ltd., Marrickville, Australia) with a temperature set at 225°C. Steaks were cooked for a predetermined time at five minutes and 45 seconds then rested 3 minutes prior to serving. Consumers rated tenderness, juiciness, flavor liking, and overall liking on 100- mm line scales. A total of seven samples were served to each consumer. Data were analyzed by muscle as a split plot design using the GLIMMIX procedure of SAS with chilling treatment as the whole plot fixed effect and postmortem aging as the sub plot fixed effect. Carcass was included as a random effect. Treatment least squares means were separated using the PDIFF option (P < 0.05).
An interaction (P < 0.01) for chilling treatment and time occurred for pH of the LT, GM, LL, PM, and SM. Initial pH for HB muscles were lower (P < 0.05) than initial pH of CB muscles. However, ultimate pH for CB muscles were lower (P < 0.05) than ultimate pH of HB muscles. An interaction (P < 0.01) was observed for chilling treatment and muscle for sarcomere length. The CB LT, LL, and PM had longer (P < 0.05) sarcomere lengths compared to their HB counterparts. The HB GM and SM had longer (P < 0.05) sarcomeres compared to CB GM and SM. The longest (P < 0.05) sarcomere lengths were observed in the CB PM.
No interactions were observed for shear force between chilling treatment and postmortem aging except in the GM (eye) and LT, where GM HB samples aged 7 d and 35 d had lower (P < 0.05) WBSF values compared to CB counterparts. The 7 d HB LT steaks had greater (P < 0.05) shear force values than any other LT regardless of chilling treatment by aging combination except for CB 21 d. Chilling and postmortem aging had no effect (P > 0.05) on GM (heart) WBSF values. Postmortem aging influenced LL and SM WBSF, but only chilling treatment affected (P < 0.05) PM WBSF.
No two way interactions for chilling treatment or aging were observed for any consumer eating quality traits. However, chilling treatment affected tenderness, juiciness, and overall liking of the LT with CB being greater (P < 0.02) than HB. Chilling treatment also affected the tenderness, flavor, and overall liking of the PM as CB was greater (P < 0.01) compared to HB. Finally, chilling treatment affected the SM for tenderness, juiciness, flavor, and overall liking; however, unlike the LT and PM, consumers scored HB SM greater (P < 0.01) than CB SM. Chilling treatment had no effect (P > 0.01) on the tenderness, juiciness, flavor, and overall liking of the GM or LL. In addition, postmortem aging affected tenderness of LT and SM with 21 d and 35 d being rated greater (P < 0.05) than 7 day samples. Postmortem aging also affected (P < 0.05) the tenderness, juiciness, flavor liking, and overall liking of the LL with consumers scoring 35 d samples most favorably, 21 d intermediate, and 7 d the lowest. Postmortem aging did not affect (P > 0.05) the tenderness, juiciness, flavor liking, or overall liking of the GM or PM. The results indicate that chilling treatment and postmortem aging had an impact on eating quality, but these results varied by muscle. Based on consumer evaluations of these five muscles, hot boning is not recommended for cube rolls or tenderloins due to the reduction of eating quality scores for these subprimals; however, hot boning and early removal of muscles like the SM benefited from an eating quality standpoint, and was neutral for the strip loin and rump. Processors must weigh the benefits and disadvantages hot boning may have on a subprimal basis when determining if this practice should be implemented in their facilities.