正交试验优化怀山药微波辅助真空冷冻干燥工艺

为获取高品质怀山药干制品，采用微波辅助真空冷冻干燥技术对怀山药进行干燥处理，并对其干燥特性及干燥品质进行评价。以物料切片厚度、真空度、微波功率为试验因素，以复水率、多糖得率及色泽明度（L）值为指标，考察干燥条件对怀山药干制品质量的影响；采用线性加权法，将多目标综合优化，确定干燥工艺的最佳参数组合。结果表明：各因素对综合指标的影响主次为：切片厚度＞真空度＞微波功率。在切片厚度5 mm、真空度100 Pa、微波功率3.75 W的条件下，微波辅助真空冷冻干燥怀山药切片达到安全含水量0.12 g/g（干基）时所需干燥时间为150 min，干燥耗能为7 875.9 kJ/kg。同时制得的干制品品质优良，复水性好，色泽洁白，多糖损失少，其复水率、L值和多糖得率分别为95.6%、92.90、18.97%。

Optimizing Microwave-Assisted Vacuum Freeze-Drying of Dioscorea opposite by Orthogonal Array Design

The microwave-assisted vacuum freeze-drying of Dioscorea opposite was executed to obtain high-quality dried
products. Drying characteristics and quality traits of dried Dioscorea opposita were investigated. The effects of three drying
conditions including sample slice thickness, vacuum degree in drying chamber and microwave power on the rehydration
ration, polysaccharide yield and L value (brightness) of dried products were examined. Linear weighting method was used
to analyze comprehensive multi-objective optimization to determine the optimal values of the studied parameters. The
results showed that the influences of these three factors on the overall index score were in the decreasing order of slice
thickness > vacuum degree > microwave power. The optimal drying conditions were slice thickness of 5 mm, degree of
vacuum of 100 Pa, and microwave power of 3.75 W. The drying time to achieve safe moisture content of 0.12 g/g (dry
basis) was 150 min and drying energy consumption was 7 875.9 kJ/kg. Under these conditions, the quality of the dried
product was excellent with good rehydration ratio (95.6%), pure color (the value of color difference was 92.90) and
high polysaccharide yield (18.97%).