Abstract: In order to investigate the effects of vacuum precooling and different circulation modes on the shelf quality of pakchoi, we simulated the circulation of the vegetable at room temperature (20 ± 1) ℃ or low temperature (4 ± 1) ℃ directly (as a control) or after vacuum precooling, and then simulated its storage at room temperature (20 ± 1) ℃ on shelves. The appearance quality and chlorophyll, carotenoids, lutein, ascorbic acid, titratable acid, soluble protein, soluble sugar, folic acid and nitrite contents of pakchoi during circulation and shelf storage were measured. The results showed that vacuum precooling could well maintain the shelf quality of pakchoi. Compared with room temperature circulation, low temperature circulation could significantly slow down the decrease in the contents of chlorophyll, carotenoids, lutein, ascorbic acid, titratable acid, soluble protein, soluble sugar and folic acid, and inhibit the accumulation of nitrite. To sum up, vacuum precooling combined with low temperature circulation can more effectively maintain the quality of pakchoi during circulation and shelf storage and inhibit the accumulation of nitrite, consequently extending the shelf life.

Key words: pakchoi; vacuum precooling; circulation modes; quality