Carcass Mass and Cooling Dynamics as Determinants of Beef Color, Tenderness, and Dark-cutting Risk

Authors

• Grace C. Johnson, University of Nebraska-LincolnFollow

First Advisor

Jordan C. Wicks

Date of this Version

5-2026

Document Type

Thesis

Citation

A thesis presented to the Faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Animal Science

Under the supervision of Professor Jordan C. Wicks

Lincoln, Nebraska, May 2026

Comments

Copyright 2026, Grace C. Johnson. Used by permission

Abstract

Discoloration in beef has important implications to the beef industry. Dark-cutting (DC) beef remains one of the most economically significant color defects; however, industry prevalence has only marginally declined (≈ 0.1%) despite mitigation efforts. This lack of improvement largely stems from research focused on pre-harvest stress and glycogen depletion leading to dark, firm, and dry (DFD) beef. However, not all darkcutting beef originates from DFD phenotypes. Atypical dark-cutting (ATDC) phenotypes have recently been observed and do not exhibit the classic metabolic indicators of DFD. This trend coincides with steadily increasing carcass weights in the beef industry and raises the possibility that carcasses of differing size respond differently to standardized chilling systems. Because lean color development is influenced by postmortem temperature and pH decline, lighter-weight carcasses may chill more rapidly, potentially contributing to darker lean color. Additionally, DC classification by United States Department of Agriculture, Agricultural Marketing Service (USDA-AMS) graders functions along a continuum rather than a strict binary threshold, suggesting biological and contextual factors may influence DC determination.

Therefore, this thesis evaluates biological mechanisms and commercial predictors associated with variation in lean color and DC classification. In a controlled experiment (n = 44 carcass sides), heavy-weight (HW; 231.4 ± 2.1 kg) and light-weight (LW; 181.1 ± 2.1 kg) carcasses were exposed to identical chilling conditions. Light-weight carcasses chilled more rapidly and exhibited darker lean color (lower L*) despite no difference in ultimate pH.

A complementary observational study of 245,681 carcass sides (DC = 0.764%) identified predictors of DC classification in a commercial beef processing facility. HCW was the most influential biological predictor, with heavier carcasses exhibiting reduced DC risk. However, grading context was the strongest predictor, as the lean color of the preceding carcass significantly influenced the probability of a USDA-AMS grader assigning a DC classification, indicating grader anchoring.

Collectively, these findings demonstrate that lean color variation arises from biological processes affecting postmortem chilling dynamics and contextual influences within commercial grading systems, highlighting opportunities to refine chilling strategies and improve lean color evaluation.

Advisor: Jordan C. Wicks