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Beef carcass weights have continued to increase over the past three decades, and trends indicate weights will continue to increase moving forward. One of the challenges with larger carcasses is altered rate of cooling. At the same time, researchers and industry members have indicated an increase in top round steak discoloration starting at fabrication and continuing through retail display. The portion of the steak that was in closest proximity to the femur bone has been noted to be lightest section of the steak. Despite these observations little is known about the impact of carcass size on visual and subsequent eating characteristics of top round steaks.
The 2015 National Beef Tenderness Survey funded by the Beef Checkoff, reported a wide range of aging time (minimum: 8 days, maximum: 100 days) for top rounds, with the average being aged for 23 days. While research has indicated extending aging times can improve the tenderness of beef, it has also indicated extended aging times can negatively impact color in the retail display case. Thus, it was important to conduct this work regarding the impact of upper limit carcass size on meat quality with regards to retail presentation and eating quality.
The primary objective of this study was to identify optimal aging conditions to achieve maximum marketability and shelf life of commercially available top rounds from varying carcass weights and aging periods to provide a more consistent and predictable retail display color and eating experience.
Average weight (AW, 750-900 lbs.; n = 21) and oversized carcass (OW, ≥ 1,000 lbs.; n = 21) were identified at a northwestern US commercial beef processing facility. Post-fabrication top rounds (IMPS #168) were collected and transported under refrigeration back to the University of Idaho Meat Laboratory. Paired top rounds were assigned to a short (8 d), average (23 d), or long (42 d) wet aging period. Once aging has been completed, the subprimals were fabricated into steaks. Steaks were assigned to one of three assignments: 1) retail display analysis; 2) objective tenderness evaluation (Warner-Bratzler Shear Force); or 3) subjective tenderness evaluation (consumer taste panel). During the retail display the following attributes were measured: steak color (objective and subjective evaluations), lipid oxidation, and color stability (oxygen consumption and metmyoglobin reducing activity).
All data were analyzed using the GLIMMIX procedure assuming a randomized complete block design with steak section treatment combination as fixed effects. Differences in the least squares means (LSM) were compared using pair-wise comparisons. Statistically significant p-values were evaluated at P < 0.05. Repeated measures were used for color analysis with day as the repeated measure and steak as the subject. All data were analyzed using SAS version 9.4 (SAS Institute, Inc., Cary, NC).
The average and oversized superficial locations retained the most favorable color characteristics throughout the retail display. Oversized deep locations were the lightest colored and most yellow of the steak section treatment combinations. Metmyoglobin reducing activity was greatest for the superficial portions. Conversely, the oxygen consumption rate was the lowest for the oversized deep steak section.
Carcasses in the oversized category of the current study are within a range that are eligible to receive heavy weight discounts on a grid-based marketing system. The current study suggested there are meaningful color differences among the anatomical sections within a top round steak among carcasses of different weights. Results indicate that oversized carcasses present a challenge in greater color variation between the superficial and deep sections of the steak. The altered color of steaks sourced from OS carcasses could lead to greater discoloration discounts at the retail sector. This research provides empirical data to help packers provide greater incentive for those cattle that fall within the more “ideal” range of hot carcass weight or increase the focus of managing carcasses exceeding 1,000 lbs. From this study we can suggest the need for an alternative management strategy to ensure those oversized carcasses are chilled in the most effective manner or that those cuts from oversized carcasses are merchandised differently.