The physicochemical characteristics of chicken breast were determined to identify the optimal ratio of CO2 and N2 to maintain chicken breast quality during cold storage for 6 d. The mixing ratios of CO2 and N2 were 20:80, 40:60, 60:40, and 80:20, respectively. The pH of the chicken breast packed with 80% CO2 and 20% N2 was lower than that of the control on day 1 (p