Effect of Plasma-Activated Water Pretreatment Combined with High-CO2 Modified Atmosphere Packaging on the Quality and Microbial Profile of Half-Smooth Tongue Sole (Cynoglossus semilaevis) During Superchilling Storage

Half-smooth tongue sole has high nutritional value due to its delicious meat and high protein content. However, its high protein content makes it highly susceptible to spoilage caused by microbial action. This study utilized plasma-activated water to pretreat half-smooth tongue sole, which was then subjected to various packaging methods: CK (air packaging), VP (vacuum packaging), MAP1 (75% CO₂/5% O₂/20% N₂), MAP2 (20% CO₂/5% O₂/75% N₂), and MAP3 (75% CO₂/10% O₂/15% N₂). The packaged samples were stored at -1 °C. Preservation efficacy was assessed by monitoring changes in microbial counts and physicochemical quality indicators throughout storage. The findings revealed a progressive increase in microbial counts, a deterioration in fish quality, and a darkening of color over extended storage periods. During superchilling storage, the increase in total volatile basic nitrogen (TVB-N) and K value was markedly reduced in the MAP1 group. Regarding protein stability, the MAP1 group exhibited a slower rise in carbonyl content as well as a slower reduction in total sulfhydryl content, further confirming its superior preservation effect. Moreover, this group demonstrated excellence in maintaining the secondary and tertiary structures of myofibrillar proteins, thereby minimizing the structural damage of fish during superchilling storage. In summary, based on observed microbial and protein changes, MAP1 (75% CO₂/5% O₂/20% N₂) was the most effective in preserving quality and extending shelf life.