Abstract: Abstract: Meat color is a major factor that influences the purchase decision by consumers as they rely on color as a visual measure of freshness and quality. Study on the relationship between metmyoglobin reducing system and meat color stability has become a major concern in the world. Metmyoglobin reductase (MetMbase) is one of key enzymes in metmyoglobin reducing system, which is mainly present in muscle mitochondria, and involves in the regulation of the oxidation-reduction reaction of myoglobin (Mb). To improve meat color stability, many researchers have focused on the effects of different treatments such as low temperature, modified atmosphere packaging and high pressure on improving its reduction activity. Among them, high pressure is considered as a meaningful method for meat processing in the future through increasing meat MetMbase activity and color stability. So, objectives of the present study were to evaluate the effects of high pressure treatments on color stability of porcine m. longissimus dorsi muscle during refrigeration storage. Porcine m. longissimus dorsi muscles with normal meat pH (5.6-5.8) were selected from 4 carcasses (Wanbai Ⅲ) for 24 h at 4℃, from a local abattoir. Samples were collected from the fresh porcine m. longissimus dorsi muscles by cutting the meat at about 2 cm from the muscle surface, and the inside meat was cut into rectangular shapes (5 cm×3 cm×2 cm) regardless of the fiber direction. The meat samples were vacuum-packaged using a polynylon pouch and kept at 4℃ prior to the pressure treatment. Samples were subjected to different pressure treatments (0.1, 50, 100, 150, 200, 250, and 300 MPa) for 10 min at 4℃, then all meat samples were removed from the pouch, put into a plastic dish, and wrapped with an oxygen permeable film (polyvinylchloride) in order to provide aerobic conditions while preventing evaporative loss during storage. Meat color (L*, a*, b*, H), Mb, MetMb, and MetMbase activity of the meat samples were evaluated after storing at 4℃ in a refrigerator for 2 weeks. Results indicated that the pressure treatment improved the MetMbase activity, which prolonged the color stability of porcine m. longissimus dorsi muscle during refrigeration storage, despite the fact that pressure treatment also resulted in irreversible Mb denaturation. Thus, it demonstrated that the meat color was affected by a balance of the metmyoglobin reducing system and by the degree of Mb denaturation. In addition, the high pressure treatment for 10 min under 150- 200 MPa at 4℃ was the optimal condition for improving the redness and MetMbase activity of porcine m. longissimus dorsi muscle during refrigeration storage. Our experiments confirm that the appropriate pressure treatment could activate MetMbase activity, and maintain the reducing state of Mb. It is beneficial to maintain the stability of meat color during refrigeration storage. In conclusion, high pressure treatment is a valuable technique that should be introduced to meat industry in China for the regulation of MetMbase activity to maintain an ideal meat color.