Project Summary

Effect of Beef Carcass Size and Aging Period on Display Color, Tenderness, and Palatability of Steaks from the Inside Round

Principle Investigator(s):
Jessica M. Lancaster 1, Tanya M. Weber 1, Jessie B. VanBuren 1, Jaxon Smart 1, Brianna J. Buseman 1, James A. Nasados 1, Gordon K. Murdoch 1, William J. Price 2, Michael J. Colle 1, Phillip D. Bass 1
Institution(s):
1 Department of Animal and Veterinary Sciences, University of Idaho
2 Statistical Programs, College of Agricultural and Life Sciences, University of Idaho
Completion Date:
August 2020

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Background 

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.

Methodology 

Average weight (AW, 750-900 lbs.; n = 21) and oversized carcass (OW, ≥ 1,000 lbs.; n = 21) were identified at a north western 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).

Findings 

Retail steak color characteristics are summarized in Table 1. 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. 

Implications 

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.

Table 1. Summary of retail display color characteristics1 for steak section treatment combination top round steaks.

 

SSTC2

 

AW3 Deep5

AW3 Sup6

AW3 Whole7

OS3 Deep5

OS3 Sup6

OS3 Whole7

Subjective Color8

Oxygenated Lean

   

High

     

Browning

 

Low

High

 

Low

High

Discoloration

 

Low

High

 

Low

High

Surface Discoloration

 

Low

 

High

Low

 

Uniformity

 

Low

   

Low

High

Objective

L*

 

Low

 

High

   

a*

           

b*

     

High

   

MRA 9

 

High

 

Low

High

 

OCR 10

High

High

 

Low

   
  • 1 For each characteristic low and high values are determined by comparing outcomes for each SSTC across retail display and aging periods. No ranking indicate SSTC was neither favorable nor unfavorable in ranking.
    2 SSTC; Steak section treatment combinations
    3 AW; steaks sourced from average carcass (340-409 kg)
    4 OS; steaks sourced from oversized carcass (≥ 454 kg)
    5 Deep; deep section
    6 Sup; superficial section
    7 Whole; intact top round steak
    8 Subjective Color Ranking: Low (favorable), High (unfavorable)
    9 Metmyoglobin Reducing Activity Ranking: Low (unfavorable), High (favorable)
    10 Oxygen Consumption Rate Ranking: Low (favorable), High (unfavorable)