基于真空预冷条件下的浸渍保鲜对鲜切莲藕品质的影响

Effect of Preservation by Impregnation under Vacuum Pre-cooling Conditions on the Quality of Fresh-cut Lotus Root

本文利用冷库(0±2℃)预冷、真空预冷及真空预冷恒压(达到终温后,继续在真空状态下维持0、2、4、6 min)等技术对经复合护色液浸渍后的鲜切莲藕进行预冷(预冷终温5℃),预冷后采用气调包装并放置于5±2℃冷库贮藏。通过测定其贮藏过程中的理化、生化指标来评价不同预冷方式对鲜切莲藕品质的影响。结果表明,真空预冷对鲜切莲藕的降温速率几乎为冷库预冷速率的10倍。随着真空预冷恒压时间的延迟,其水分损失呈增加的趋势,同时差异性显著(P<0.05),但对莲藕的外观差异并不显著(P>0.05)。真空预冷至5℃并维持2、4、6 min所获得的理化、生化及营养指标值较对照组而言更接近新鲜莲藕,特别是其不仅能够降低多酚氧化酶(PPO)的最大峰值,同时还能够推迟峰值出现的时间。其中,真空预冷至5℃并维持4 min效果最佳。

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.