The physicochemical characteristics of chicken breast were determined to identify the optimal ratio of CO_2 and N2 to
maintain chicken breast quality during cold storage for 6 d. The mixing ratios of CO_2 and N_2 were 20:80, 40:60, 60:40, and
80:20, respectively. The pH of the chicken breast packed with 80% CO_2 and 20% N_2 was lower than that of the control on
was found for redness (a^*) and yellowness (b^*). A lower volatile basic nitrogen level was found for chicken breasts
exposed to higher CO_2 levels. Furthermore, lipid oxidation of the chicken breast packed with CO_2 decreased with increasing
CO_2 level, and 40% CO_2 significantly reduced 2-thiobarbituric acid reactive substances (TBARS) values on days 1 and 6.
The total number of microbes was reduced in chicken breast exposed to more than 40% CO_2 during storage days 3 and 6
CO_2 level on storage day 3. Moreover, tray-packed chicken breast exposed to 40% CO_2 did not collapse. These results suggest
that 40% CO_2 and 60% N_2 were the optimal conditions for packaging chicken breasts during cold storage.