Studies On Drying Process Of Rehmannia Leaves Extract And Radix Paeoniae Rubra Extract

Vacuum belt drying (VDB) process of Rehmannia Leaves extract and microwave vacuum drying process of Radix Paeoniae Rubra extract were investigated in this paper.The operation parameters of VBD and microwave vacuum drying process were studied.The studies would be contributed to the foundation of technical standards and application rules of VBD and microwave vacuum drying technique for Traditional Chinese Medicine (TCM). The major research content is as follows:1. Based on the single factor test, the Vacuum belt drying (VDB) process of Rehmannia Leaves extract was studied by using orthogonal test design,combined with analysis of variance and grading method for multiple-index on the parameters of the water content of dried product and active ingredient retention rate of Rehmannia Leaves extract.Then,compare the optimum process of vacuum belt drying with the vacuum oven drying and the microwave vacuum drying methods.The key technical parameters impacting the water content of the dried product are listed as follows:the feeding speed,the belt speed and heating system temperature.The critical technical parameter impacting the drying process is the belt speed. The optimum process determined by the grading method for multiple-index was listed as follows:the belt speed was 4 cm·min-1,the feeding speed was 25 mL·min-1,the drying temperature was(75℃,75℃).In this process parameters, the water content of dried product is 2.54%, the retention rate of verbascoside and total glycosides are 94.47% and 90.70% respectively. Compared with the vacuum oven drying and the microwave vacuum drying methods, the vacuum belt drying technology can continuous production and the drying product of this technology has high quality with lower water content,higher active ingredient retention rate and shorter drying time.2. Drying curves (moisture content vs. drying time) under different drying conditions were plotted. Eight mathematical models were proposed for simulation of vacuum belt drying of Rehmannia Leaves extract. The Page model was found to be the most suitable model for describing drying behavior of Rehmannia Leaves extract.3. The microwave vacuum drying process of Radix Paeoniae Rubra extract was studied in this paper. The effects of various processing conditions,such as microwave power,sample load,on the changes of the moisture content,temperature,dehydrating rate and the content of the active components of Radix Paeoniae Rubra extract was analyzed and the drying curve was drawn. The drying process could roughly be divided into three stages:The accele rate period the constant rate period and the falling rate period. The critical technical parameter impacting the drying process is microwave power.Under microwave condition,the highest temperature of material is not more than 80℃, and the degradation amount of Paeoniflorin is little during the microwave vacuum drying process.4. Five mathematical models were proposed for simulation of drying characteristics of Radix Paeoniae Rubra extract.The results showed that the drying procedure of Radix Paeoniae Rubra extrac could accurately be described by the Page model, the predicted values of the model were nearly consistent with the observed values.The moisture contents and dehydrating rate during the drying procedure can be exactly estimated by it.