Change in Myoglobin Denaturation and Physiochemical Properties Among Three Degrees of Doneness and Three Beef Whole Muscles

Abstract

While the factors impacting raw meat color have been extensively explored, the factors affecting cooked meat color have been largely ignored, leaving a gap in research. Establishing a baseline for the changes that accompany different degrees of doneness (DOD) could serve as the foundation for future studies to further understand what factors are impacting differences in cooked color of whole muscles. Beef strip loins (n=12) and top butts (n=12) were used to evaluate the Longissimus dorsi (LD), Biceps femoris (BF), and Gluteus medius (GM) between 3 DOD: medium rare (62.8°C), medium (71.1°C), and well-done (76.7°C). Immediately after cooking, steaks were sliced, evaluated for L*, a*, b*, frozen in liquid nitrogen, and blended into a powder for lab assays including myoglobin denaturation, metmyoglobin-reducing activity (MRA), surface hydrophobicity, proximate analysis, and lipid oxidation. An additional steak was cooked for shear force and cook loss. As expected, the a* values decreased (P<0.05) and myoglobin denaturation percentages increased (P<0.05) with increasing DOD, while muscle source did not impact (P>0.05) either. Surface hydrophobicity, which is a measure of exposed hydrophobic groups caused by denaturation, increased (P<0.05) with increasing DOD, while MRA decreased (P<0.05) with each DOD. However, the BF and GM muscles resulted in greater (P<0.05) MRA compared to the LD. There was an interaction (P<0.05) for lipid oxidation. As DOD increased past the raw state, differences inoxidation between muscles emerged. While the factors evaluated among the DOD were impacted, muscle type surprisingly affected most assays evaluated as well. This study can serve as a foundational paper to support future cooked color research to further understand what factors impact cooked color and cooked color stability of whole muscle cuts.