雪莲果热风-微波联合干燥工艺优化

Process Optimization for Drying of Yacon by Hot Air Combined with Microwave

以雪莲果为原料,研究样品厚度、热风温度、微波质量比功率对雪莲果热风和微波干燥特性的影响。以热风温度、转换点含水率、微波质量比功率为因素,以色泽变化(ΔE)、干燥时间(t)为指标,采用二次回归正交旋转组合试验设计确定雪莲果热风-微波联合干燥的最适工艺参数。结果表明:雪莲果热风干燥最适工艺参数组合为样品厚度2～4mm,热风温度70℃;雪莲果微波干燥最适工艺参数组合为样品厚度4mm,微波质量比功率2W/g。影响热风-微波联合干燥产品ΔE的主次顺序依次为微波质量比功率、热风温度、转换点含水率;影响干燥时间的主次顺序依次为转换点含水率、热风温度、微波质量比功率。雪莲果热风-微波联合干燥的最适工艺参数组合为热风温度68.1℃,转换点含水率61.0%,微波质量比功率2.6W/g。在此组合参数条件下,色泽变化ΔE=21.53,干燥时间t=172min,复水比RR=4.12,收缩率SR=84.35%。

In this work,hot air and microwave were combinedly used to dry yacon and its drying characteristics were explored under varying conditions of sample thickness,air temperature,and microwave power.Quadratic regression orthogonal rotary combination design was used to optimize total color change（ΔE） and drying time with respect to hot air temperature,water content at conversion point and microwave mass specific power.The results showed that the optimal process parameters of hot air drying were sample thickness of 2-4 mm,air temperature of 70 ℃ and those of microwave drying were sample thickness of 4 mm and microwave mass specific power of 2 W/g.The importance of factors affecting ΔE resulting from hot air combined with microwave treatment dropped in the following sequence： microwave mass specific power,hot air temperature and water content at conversion point,and water content at conversion point was the most important factor affecting drying time,followed by hot air temperature and microwave mass specific power.The optimal parameters for drying yacon by hot air combined with microwave treatment were sample thickness of 4 mm,hot air temperature of 68.1 ℃,water content at conversion point of 61.0% and microwave mass specific power of 2.6 W/g.Under the optimal process conditions,the color change ΔE was 21.53,the drying time t 172 min,the rehydration rate RR 4.12,and the shrinkage rate SR 84.35%.