Meat color is an important indicator for consumers to choose meat products. Whether raw or cooked, dark, firm, and dry (DFD) beef has color defects. The dark purplish red color of raw DFD beef is disliked by consumers, causing downgrading of its quality and consequently economic loss. DFD beef still exhibit a pink color when overcooked, causing a decline in quality attributes such as tenderness and juiciness. In this context, this paper reviews the mechanism of color formation in raw and cooked DFD beef, and examines recent progress in the application of modified atmosphere packaging (MAP), organic acid treatment, and temperature control to overcome the color problem of DFD beef. We hope that this review will provide a reference for solving this problem in the future.

In order to explore the effect of pH on the structure and thermal stability of myoglobin, the molecular structure and surface hydrophobicity of myoglobin at normal pH (5.6) and high pH (6.4) under refrigerated (4 ℃) and heating (72 ℃) conditions as well as its thermal denaturation degree were characterized by various spectroscopic techniques. The results showed that pH had no significant effect on the conformation of myoglobin at 4 ℃. However, the endogenous fluorescence intensity, protein surface hydrophobicity and thermal denaturation of myoglobin at 72 ℃ were significantly higher at pH 5.6 than at pH 6.4. The tertiary structure of myoglobin was more severely destroyed at pH 5.6 than pH 6.4, resulting in reduced thermal stability. Therefore, environmental pH can affect the thermal stability of myoglobin by altering its structural stability. High pH can increase the thermal stability of myoglobin, which is an important cause for the persistent pink color of dark, firm, dry (DFD) beef during cooking.