[Drying Process and Model of Banqiao Codonopsis Radix Slice in Air-impingement Jet Dryer]

To determine the drying process and to built model of Banqiao Codonopsis Radix slices dried in air-impingement jet dryer.

With taking the content of polysaccharides( CPPS),rehydration ratio( RR) and drying time as the evaluation indexes,the effects of drying temperature( 40,50,60 and 70 ℃),slices thickness( 1,2,3 and 4 mm) and air velocity( 8,10,12,and 14 m / s) on the content of CPPS,RR and drying time were studied. With taking the R2,χ2and RMSE as the evaluation indexes,the optimum model was screened by fitting the drying curves data with four selected models.

The variety of all studied factors lead to change of the content of CPPS,RR and drying time,and the influence of air-temperature was most significant. Under the test conditions,the content of CPPS,RR and drying time were range from 20. 33% ~ 28. 26%,2. 65 ~ 3. 25 and 180 ~ 510 min, respectively. Among the four selected drying models, Modified Page model was the most suitable model to fit the drying curves data with the maximum average of R2( 0. 9993),the smallest average of χ2( 0. 00022) and the smaller average RMSE( 0. 01066).

By comparison the content of CPPS,RR and drying time, the optimal drying process of Banqiao Codonopsis Radix slices dried in the air-impingement jet dryer was air temperature of 60 ℃,slice thickness of 2 mm and air velocity of 12 m / s. Under the drying conditions of air temperature 40 ~ 70 ℃,slice thickness 1 ~ 4 mm and air velocity 8 ~ 14 m / s, Modified Page model can effectively predict the moisture change of Banqiao Codonopsis Radix slice dried in air-impingement jet dryer.