Abstract The effects of prefreezing on the drying rate, internal structure and mechanical properties of apple fruit processed by microwave-vacuum drying (MVD) were evaluated. The drying rate of the prefrozen sample was approximately 1.2–1.3 times higher than that of the nontreated sample. In the frozen-thawed tissue, damage to the cell wall structure and cell membrane due to ice crystal formation during freezing was confirmed; thus, improvement in the drying rate was suggested to be the result of accelerated water transfer in the tissue. Structural observation using X-ray computed tomography showed that the prefrozen MVD sample had a porous internal structure with larger voids than air dried or nonpretreated samples. Alterations in the mechanical properties, such as higher maximum stress and number of peaks during the puncture test, indicating a softer and crisper texture, were observed in the prefrozen MVD sample.

中文翻译：

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预冻对微波真空苹果干干燥特性、结构形成和力学性能的影响

摘要 研究了预冻对微波真空干燥（MVD）处理后的苹果果实的干燥速率、内部结构和力学性能的影响。预冻样品的干燥速率比未处理样品的干燥速率高约 1.2-1.3 倍。在冻融组织中，证实冷冻过程中形成冰晶对细胞壁结构和细胞膜造成损伤；因此，干燥速率的提高被认为是组织中水分转移加速的结果。使用 X 射线计算机断层扫描的结构观察表明，与风干或未经预处理的样品相比，预冷冻的 MVD 样品具有多孔内部结构，空隙更大。机械性能的变化，例如在穿刺测试期间更高的最大应力和峰值数量，