Abstract Rapid/moderate/slow pressure reduction modes of vacuum cooling (VC) with pressure reduction rates ranging from 0.0043 to 0.0502 s-1 were developed. The effects of VC in different modes on the cooling efficiency and quality-related attributes of different edible parts of pakchoi including total and free water contents, colour differences, respiration rates, membrane stability and microstructures were investigated, and the cluster analysis (CA) was employed for visualizing and classifying the VC-induced quality variation. Results showed that the leaf and the petiole exhibited different temperature changes and vacuum tolerances, of which the adaxial epidermis of the leaf was more sensitive to VC, showing more severe cell damage due to the internal moisture gradient. The rapid pressure reduction mode (α1 = 0.0502 s-1) could predominately improve cooling efficiency and minimize the quality attenuation, while the moderate pressure reduction mode (α2 = 0.0184 s-1) contributed to better temperature uniformity and colour acceptance. Moreover, the result of CA further confirmed the above conclusions, suggesting that α1 and α2 endowed pakchoi with similar quality-related attributes to the fresh one. The current study proved that the slow pressure reduction mode should be avoided for uses in VC of leafy vegetables.

中文翻译：

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减压方式对小白菜不同部位真空冷却效率及品质相关属性的影响

摘要 开发了减压速率范围为0.0043~0.0502 s-1的真空冷却（VC）快速/中速/缓慢减压模式。研究了不同模式下 VC 对小白菜不同可食部分的冷却效率和质量相关属性的影响，包括总和游离水含量、颜色差异、呼吸速率、膜稳定性和微观结构，并进行聚类分析 (CA)用于可视化和分类 VC 引起的质量变化。结果表明，叶片和叶柄表现出不同的温度变化和真空耐受性，其中叶片的正表皮对VC更敏感，由于内部水分梯度显示出更严重的细胞损伤。快速减压模式（α1 = 0. 0502 s-1) 可以主要提高冷却效率并最大限度地减少质量衰减，而适度的减压模式 (α2 = 0.0184 s-1) 有助于更好的温度均匀性和颜色接受度。此外，CA的结果进一步证实了上述结论，表明α1和α2赋予了小白菜与新鲜小白菜相似的品质相关属性。目前的研究证明，在叶类蔬菜的VC中使用应避免缓慢减压模式。表明 α1 和 α2 赋予小白菜与新鲜小菜相似的质量相关属性。目前的研究证明，在叶类蔬菜的VC中使用应避免缓慢减压模式。表明 α1 和 α2 赋予小白菜与新鲜小菜相似的质量相关属性。目前的研究证明，在叶类蔬菜的VC中使用应避免缓慢减压模式。