Relationships of myoglobin forms at grading to beef longissimus thoracis lean color, color stability, and tenderness

Authors: King, David; Shackelford, Steven; Wheeler, Tommy

Submitted to: Meat and Muscle Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2025
Publication Date: 6/1/2026
Citation: King, D.A., Shackelford, S.D., Wheeler, T.L. 2026. Relationships of myoglobin forms at grading to beef longissimus thoracis lean color, color stability, and tenderness. Meat and Muscle Biology. 10(1). Article 20497. https://doi.org/10.22175/mmb.20497.
DOI: https://doi.org/10.22175/mmb.20497

Interpretive Summary: The pigment responsible for the color of the muscle, myoglobin, binds oxygen when exposed to air to create the characteristic cherry-red color associated with beef. Beef carcasses are cut, exposing the ribeye muscle to air, prior to grading. Numerous factors affect the amount of oxygen available for binding in muscle, most notably, oxygen consumption by mitochondria in the muscle. Oxygen consumption affects beef color and tenderness and oxygen binding may be useful as an indicator of oxygen consumption. In this study we tested three methods to estimate the extent of oxygen binding in the ribeye and the relationship between oxygen binding by the ribeye at grading to color and tenderness. We found that all three methods could differentiate the amount of oxygen binding occurring in the ribeye, but the estimates were only accurate for relative differences rather than absolute values. Moreover, more extensive oxygen binding resulted in less stable color during retail display but more tender steaks. Rapid methods for measuring the extent of oxygen binding during the grading process could predict color and tenderness traits thus identifying beef that is more valuable for targeted marketing strategies.

Technical Abstract: We compared 3 methods (Piao, Krzywicki, and K/S) for estimating myoglobin forms of longissimus thoracis surfaces exposed by ribbing (ribeye) for grading in the unbloomed and bloomed state and evaluated the relationship between oxymyoglobinin the bloomed ribeye surface to lean color, color stability, and tenderness. Spectral data were obtained on the ribeye of 485 beef carcasses in 2 plants immediately after ribbing and at grading. Longissimus thoracis steaks were placed in a simulated retail display to assess color stability. Slice shear force was determined at 14 d postmortem. All methods detected differences (P < 0.05) in oxymyoglobin and deoxymyoglobin across bloom status and processing plants. Estimates of each myoglobin form in bloomed ribeyes were highly correlated (P < 0.05) with estimates of the same form from othr methods. Estimates of deoxymyoglobin and metmyoglobin where highly correlated (P<0.05) across methods in unbloomed ribeyes. In unbloomed ribeyes, estimates of oxymyoglobin from the Piao and Krzywicki methods were not correlated to K/S610/K/S572 values (r=-0.09 and 0.14, respectively; P>0.05). The Piao and Krzywicki estimates differed in magnitude and generated values outside the range of 0 to 100%. Lean color, color stability, and slice shear force all differed (P < 0.05) across plants. Increased oxymyoglobin in the bloomed ribeye resulted in increased instrumental color values of longissimus thoracis steaks early in display. Increased oxymyoglobin at grading resulted in slight decreases in color stability. Slice shear force decreased with increased oxymyoglobin in the ribeye at grading, but the extent to which increased oxymyoglobin impacted slice shear force differed across plants. These data suggest that all 3 methods can differentiate samples regarding myoglobin forms, but absolute values should be interpreted with caution. The extent of oxymyoglobin formation at the time of grading is associated with both tenderness and color traits.