Effect of Preservation by Impregnation under Vacuum Pre-cooling Conditions on the Quality of Fresh-cut Lotus Root
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Abstract:
Different technologies, including cold storage room pre-cooling, vacuum pre-cooling, and vacuum pre-cooling coupled with constant pressure treatment (when the final temperature was reached, the vacuum pump and valve were closed for 0, 2, 4, and 6 min, respectively), were utilized to pre-cool (final pre-cooling temperature: 5 ℃) fresh-cut lotus root that was impregnated in the compound fresh-keeping solution for 12 min. After pre-cooling, all samples were packaged in a modified atmosphere and stored in the cold storage room (5 ± 2 ℃). The effects of different pre-cooling methods on the quality of fresh-cut lotus root were evaluated by measuring the physiochemical and biochemical indexes during the storage. The experimental results showed that the cooling rate of vacuum pre-cooling was almost ten times that of cold room pre-cooling. In the cooling process when a constant pressure was maintained for a long duration, a significant trend towards increased water loss was observed (P < 0.05), while no significant difference was observed in the overall appearance (P > 0.05). The physicochemical and biochemical indexes obtained for the fresh-cut lotus root that was vacuum pre-cooled to 5 ℃ followed by maintenance at constant pressure for 2, 4, and 6 min were similar to that of the fresh lotus roots than that of the control group. In particular, vacuum pre-cooling coupled with constant pressure treatment not only reduced the maximum peak value of polyphenol oxidase (PPO) activity, but also prolonged the time to reach such a peak value. The best preservation effect was achieved when the sample was vacuum pre-cooled to 5 ℃ and constant pressure was maintained for 4 min.
