Study on parameters of freezing combined with microwave drying characteristics of polygonum cuspidatum

Polygonum cuspidatum slices were freezing dried transferred to microwave dried.The transfer point of the two drying methods were studied and validated based on the microstructure.In addition,drying rate and quality of samples with different parameters was studied. Sample quality was compared in terms of medicinal ingredients( polydatin,emodin,physcion,resveratrol),color,volume retention rate,rehydrated ratio. The result showed that quality of samples for 5 mm dried with 40 Pa,heating plate for 40 ℃ and transferred at the moisture content of 25%to microwave at 60 ℃ would be closed to samples dried with freezing drying.In addition,it costs half of drying time as freezing drying.