Influence of microwave vacuum drying on the effective moisture diffusivity of seedless white grapes

Abstract In this study, the effects of microwave power, vacuum degree and load weight on the moisture content of seedless white grapes (Vitis vinifera L.) during microwave vacuum drying were investigated. The result found that during microwave vacuum drying, the effective moisture diffusivity (Deff) of seedless white grapes ranged between 1.0232 × 10−9 and 4.6354 × 10−9 m2/s. The Deff values increased with the increase in the microwave power and the decrease in the load weight, the vacuum degree played a relatively minor role. The kinetics of moisture ratio and drying time were established, with the drying process following the Page model, as reflected by the fitting between model-predicted and measured data. The Page model was demonstrated to precisely describe and predict the moisture content variation in seedless white grapes during microwave vacuum drying.

摘要 本研究考察了微波功率、真空度及装载量对无核白葡萄（Vitis vinifera L.）微波真空干燥过程中含水率的影响。研究结果表明，在微波真空干燥过程中，无核白葡萄的有效水分扩散系数（effective moisture diffusivity，Deff）介于1.0232×10⁻⁹ 至4.6354×10⁻⁹ m²/s之间。Deff值随微波功率升高、装载量降低而升高，真空度的影响相对较小。本研究建立了水分比与干燥时间的动力学模型，干燥过程符合Page模型，模型预测值与实测数据的拟合结果验证了这一点。研究证实Page模型可精准描述并预测无核白葡萄在微波真空干燥过程中的含水率变化规律。