Source: South Dakota State University Extension
Clay J. Carlson, Christina E. Bakker, Keith R. Underwood, Amanda D. Blair, Judson K. Grubbs
Rationale and Approach
Proteolysis is the breakdown or degradation of proteins that causes meat to become more tender as it ages. Analyzing proteolysis can refine understanding and improve prediction of tenderness in beef. Proteolysis of desmin, a protein that aids in keeping muscle structure organized, has been correlated with tenderness. In a live animal, desmin would be intact. As muscle ages postmortem, the intact desmin is degraded. Due to the correlation between desmin degradation and tenderness values, measuring the disappearance of intact desmin can indicate differences in tenderness between samples. Many factors influence the proteolysis of desmin postmortem. One factor that could influence the proteolysis of desmin that is not well understood is the animal’s weight at slaughter. Cattle producers strive to increase average daily gain and feed conversion, resulting in heavier cattle at
younger ages. Meat processors can improve efficiency by increasing rail weight given the same number of carcasses. As a result, average beef hot carcass weight (HCW) has increased by approximately 165 pounds in the last 30 years (USDA-ERS, 2022). This study aimed to determine the influence of beef HCW on the proteolysis of desmin in four muscles: the eye of round, New York (NY) strip, ribeye, and Denver cut. Twelve carcasses were categorized in two groups: Heavyweight (HW; HCW = 973-1,007 lbs.) or Lightweight (LW; HCW = 753-787 lbs.). Samples were collected from the muscles listed above at 2, 4, 6, 8, 12, 24, and 48 hours, 5 and 10 days postmortem. After collection, samples were vacuum packaged and frozen until analyzed. To analyze proteolysis, proteins were
separated using SDS-PAGE gels. Western blotting methods were used to image and analyze the disappearance of intact desmin.
Findings
No HCW by aging time interactions were detected in any of the muscles evaluated. In the Denver cut and ribeye, there was less proteolysis in the HW group (Figure 1). There was no difference in proteolysis between the weight groups in the NY strip and eye of round (Figure 1). In all four muscles, desmin degraded throughout aging (Table 1). In the Denver cut and the eye of round, there were no differences in degradation until 5 and 10 days postmortem. In the ribeye and NY strip, degradation differences were detectable as early as 8 hours postmortem, indicating proteolysis began earlier in these muscles.
Implications
Carcass weight alters total desmin proteolysis in the Denver cut and ribeye, which could result in decreased tenderness in HW carcasses in those muscles. These data suggest that the contribution of proteolysis to tenderness of NY strip and eye of round steaks will not be affected by the size of the beef carcass slaughtered. Other factors, such as rigor, pH, and connective tissue, can also influencetenderness. Therefore, further research should be conducted to determine the effects of HCW on meat quality.
Acknowledgements
This project was supported by the Beef Checkoff through the South Dakota Beef Industry Council (Award # 3X0395) and USDA NIFA (Accession # 1025033).
References
USDA-ERS. 2022. Historical livestock and poultry live and dressed weights. Livestock Meat Domestic Data. doi: https://www.ers.usda.gov/data-products/
