In order to explore dynamic changes in the physicochemical characteristics and microbial diversity of modified atmosphere packaged braised chicken during refrigeration, high-throughput sequencing technology and traditional isolation and identification methods were combined to study the physical and microbial changes of modified atmosphere packaged (25% CO₂/75% N₂) braised chicken during storage at 4 ℃ for 10 days. The results showed that total volatile basic nitrogen (TVB-N) content and total bacterial count increased significantly during storage (P < 0.05). pH decreased significantly in the late storage period (P < 0.05). Thiobarbituric acid reactive substance (TBARS) levels tended to be stable at the end of storage (P > 0.05). These changes were related to the gas composition in modified atmosphere packaging. The microbial species richness of braised chicken was the highest at the early stage of storage, and then decreased gradually. At the initial stage of storage, the relative abundance of Enterobacteriaceae, Acinetobacter and Aeromonas were high. At the middle and late stages of storage, the relative abundance of Weissella and Enterobacter were high. The relative abundance of Weissella, Enterobacter, Lactococcus and Leuconostoc increased gradually during the whole storage period and their growth was dominant. Six species of spoilage organisms were isolated and identified, namely, Lactobacillus curvatus, Bacillus cereus, Bacillus safensis, Serratia liquefaciens, Hafnia sp. and Enterobacter sp., which could be the major causes of the rot of braised chicken under modified atmosphere packaging conditions.

The purpose of this study was to clarify the effect of the combination of antifreeze and immersion freezing on the quality of frozen prepared beef steaks. Four groups were set up: ⅰ) control group, vacuum packaging before frozen storage; ⅱ) antifreeze group, incorporation of antifreeze during tumbling vacuum; ⅲ) immersion freezing group; and ⅳ) antifreeze + immersion freezing group. Beef steaks were frozen at -30 ℃ for up to 90 days. The thawing loss, juice loss, cooking loss, texture characteristics, shear force, color and thiobarbituric acid reactive substances (TBARS) value were measured after 0, 30, 60 and 90 days, and the microstructure was observed. The results showed that compared with the other treatment groups, the thawing loss, juice loss, cooking loss and TBARS value were significantly decreased in the antifreeze + immersion freezing group. In addition, for the combined treatment group, the brightness and redness values were higher, and muscle fiber arrangement was orderly and tightest among the four groups. Conclusion: The combination of immersion freezing and antifreeze can not only make the tissue structure of prepared beef steaks more compact to maintain better water retention capacity, but also keep its color stability.