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Objective: This study aimed to investigated the effect of ice-temperature vacuum drying on the powder quality of selenium-rich Rugao black pakchoi. Methods: After pretreatment, the fresh black pakchoi was dried to the moisture content of (5.0±0.5) %, and the physical and chemical indexes were investigated, comparing to the control groups of hot-air drying, vacuum drying and freeze-vacuum drying. Results: The vitamin C content of vacuum drying at ice temperature was 554.60 mg/100 g, and the retention rate reached 83.96%, which was 43.11%, 33.57% and 1.61% higher than that of hot-air drying, vacuum drying and freeze-vacuum drying, respectively. Glutathione peroxidase had little activity loss and the best purity maintenance. The retention rates of total phenols and total flavonoids were 59.69% and 60.58%, respectively, which were better than the other three groups. In terms of microstructure, the powder of ice-temperature vacuum drying group was well-distributed, with a smooth and flat surface and less debris. Compared with the other three groups, the ice-temperature vacuum drying group could maintain the original dark green color, and the rehydration and solubility were improved. Conclusion: The ice-temperature vacuum drying process can minimally affect the Rugao black pakchoi powder, and the nutritional quality of this powder is the highest.

Objective: The effect of frozen temperature on the storage characteristics of ready-to-eat snakehead sausages were investigated. Methods: In this study, The freezing temperature dehydration technique was used to control the moisture content of snakehead sausage at about 50%, and then the temperature was lowered to-5.6 ℃. Subsequently, the sausage was stored at -4 ℃, and those stored at 4 ℃ were set as the control. The changes in the quality and microstructure of the snakehead sausages were analyzed, by measuring the physicochemical indexes such as total bacterial colony, color, water holding capacity, textural properties, biogenic amines and scanning electron microscopy during storage. Results: The logarithmic values of TVC were （5.37±0.06）; TVB-N were （17±0.03） mg/100 g; the total amine mass fraction were （324.93±1.89） mg/kg at 42 d. The results of colony count and TVB-N analysis showed that, compared to those stored at 4 ℃, frozen storage could extend the shelf life of snakehead sausage by 1-fold. The low-field NMR results showed that the moisture distribution of snakehead sausage during frozen storage was better than that of the control. Scanning electron microscopy showed that the gel network of the frozen-storage group had a higher degree of binding to fat particles. The frozen storage of snakehead sausage was superior to the refrigerated storage. Conclusion: The preservation effect of snakehead sausage stored at freezing temperature is better than that of refrigerated storage.