Abstract: This study investigated the effect of modified atmosphere packaging (MAP) containing a mixture of O2 and CO2 on the quality and microbial community structure of fresh Asian swamp eel (Monopterus albus) during refrigerated storage. Fresh eel samples were packaged under two MAP conditions: an anaerobic mixture (CA, 30% CO2 + 70% N2) and an aerobic mixture (CA-O2, 20% O2 + 30% CO2 + 50% N2). Air packaging was used as a control. Over a 12-day storage period at 4 ℃, changes in physicochemical indices including pH, total viable count (TVC), total volatile basic nitrogen (TVB-N) content, thiobarbituric acid reactive substances (TBARS) value, color parameters (a* value), myoglobin (Mb), and metmyoglobin (MetMb) content were measured. High-throughput sequencing (HTS) was employed to analyze microbial community composition and succession, and gas chromatography-ion mobility spectrometry (GC-IMS) was used to analyze dynamic changes in volatile flavor compounds. The results indicated that both CA and CA-O2 treatments significantly suppressed the increase in TVB-N and TVC compared with the control group (P < 0.05). Furthermore, the CA-O2 group maintained a higher a* value than the CA group throughout storage, reaching 4.30 on day 12, which was significantly higher than that of the CA group (P < 0.05), together with a 79.6% increase in Mb content. Additionally, both MAP treatments significantly reduced the relative abundance of specific spoilage organisms such as Pseudomonas and Acinetobacter (P < 0.05), and effectively limited the accumulation of undesirable flavor compounds including 1-propanethiol, 2-propanethiol, and trimethylamine while increasing the level of ethyl formate, which can help counteract off-odors. Pearson correlation analysis revealed that in the CA-O2 group, color scores exhibited strong positive correlations with odor and overall acceptability (r > 0.93, P < 0.001). Moreover, in all groups, the TVC and the relative abundances of the major spoilage bacteria (Acinetobacter, Pseudomonas) were significantly negatively correlated with the sensory scores (odor, color, overall acceptability) (P < 0.05). In conclusion, the CA-O2 group was more effective than the control group in inhibiting spoilage and outperformed the CA group in preserving the color and flavor. This study provides a theoretical foundation and technical support for developing novel MAP strategies for achieving both high antimicrobial efficacy and superior color preservation in fresh M. albus.

Key words: Monopterus albus; O2-containing modified atmosphere packaging; refrigeration; color; microbial community; volatile flavor compounds