Microwave pre‐treatment for vacuum drying is a promising method in order to enhance heat and mass transfer rate. In this study, the influences of microwave pre‐treatment (90 W 30 min) on vacuum drying conducted at different combinations of drying temperature and absolute pressure (60, 70, and 80°C with 15 and 30 kPa) were investigated by evaluating the drying characteristics, rehydration capacity, and some quality attributes of orange slices. The vacuum drying treatments were carried out both with (MWVD) and without the microwave‐pretreatment (VD) at the same temperature and absolute pressure combinations. It was revealed that application of MWVD shortened the drying time of orange slices while increasing drying rate, effective moisture diffusivity and rehydration capacity. Six different semi‐theoretical mathematical models were applied, and Page, Modified Page, Logarithmic, and Lewis models were best fitted to experimental data of orange slices. It was observed that, among the different drying conditions applied in the scope of the study, VD at 80°C–15 kPa caused lowest color change (ΔE) that indicates the difference between the dried and fresh orange slices. All drying treatments caused a reduction in ascorbic acid content (AAC) (56.24–59.34%), total phenolic content (TPC) (15.92–55.79%) and total antioxidant capacity (TAC) (6.05–35.18%, 21.03–42.28%, and 54.76–69.07% for DPPH, FRAP, and CUPRAC assays, respectively) of orange slices. When MWVD and VD were compared, it was observed that MWVD caused less decrease in TPC and more in AAC and TAC. In conclusion, MWVD method is suggested as the more effective method providing lower drying time, faster drying rate, and better quality parameters of the product.

中文翻译：

---

微波预处理橙片的干燥：干燥特性，复水能力和质量特性

为了提高传热和传质速率，对真空干燥进行微波预处理是一种很有前途的方法。在本研究中，通过评估微波预处理（90 W 30分钟）对干燥温度和绝对压力（60、70和80°C在15和30 kPa的不同组合）下进行的真空干燥的影响，橙片的干燥特性，补水能力和一些品质属性。真空干燥处理是在相同的温度和绝对压力组合下使用（MWVD）和不使用微波预处理（VD）进行的。结果表明，MWVD的使用缩短了橙片的干燥时间，同时提高了干燥速率，有效的水分扩散性和复水能力。应用了六个不同的半理论数学模型，修改后的Page，对数和Lewis模型最适合橙片的实验数据。观察到，在研究范围内使用的不同干燥条件中，VD在80°C–15 kPa下引起的色变最小（ΔE）表示干燥的和新鲜的橙片之间的差异。所有干燥处理均导致抗坏血酸含量（AAC）（56.24–59.34％），总酚含量（TPC）（15.92–55.79％）和总抗氧化剂容量（TAC）（6.05–35.18％，21.03–42.28％）降低，橙片的DPPH，FRAP和CUPRAC分析分别为54.76–69.07％）。当比较MWVD和VD时，观察到MWVD引起的TPC降低较少，而AAC和TAC引起的增加更多。总之，建议使用MWVD方法作为更有效的方法，该方法可缩短干燥时间，加快干燥速度并提供更好的产品质量参数。