Study On The Impact Drying Technology Of Dangshen Gas Jet

Codonopsis piousula contains Codonopsis pilosula polysaccharide, saponin, alcohols, triterpene, volatile oils, alkaloids, essential amino acids, inorganic elements and many other nutritional ingredients, it is edible and has many pharmacological efficacy, such as profiting spleen and lung. But fresh Codonopsis cannot be easy storaged for a long time as its high water content, so dehydration dried is an effective method to extend its storage period, but the present main drying method of Codonopsis piously are natural drying (ND) and hot-air drying (HD); however ND is time consuming, easily affected by weather and site, and it's difficult to control product quality; HD is high energy consumption and poor product quality. But Air-impingement jet drying (AIJD) has the advantage of higher drying rate, higher drying efficiency, lower energy consumption and better product quality compared with ND and HD when applied in drying agricultural products. In this paper, the AIJD technology were applied to dry Codonopsis slices for the purpose of improving product quality, reducing drying time and lowing energy consumption, the drying dynamics and processing were studied; moreover, the effects of AIJD combine microwave drying (MD) on the drying time, the unit energy consumption and quality of Codonopsis slices were discussed. The main achievements were as follows:1 Codonopsis slices AIJD was a falling rate drying, the drying air temperature, slice thickness and wind velocity had distinctly effect on the drying curves, drying rate curves and water effective diffusion coefficient (Deff). Under the experimental condition, Deff was in the range of (3.4799-7.1485) ×1010 (m2·s-1), which increased with the temperature and air velocity increase, but decreased with the slice thickness increase; Codonopsis pilosula dry activation energy was 16.98 KJ/mol.2. Modified Page model was the optimal drying model of Codonopsis slices dried in AIJD and the dynamics model equation we obtained was as follows: MR=exp{-[(0.10001-0.00506A+0.00523B+0.00309C-0.00005AB+0.0000167AC-0. 000375BC+0.0000556A2+0.000119B2-0.000114C2)t](-0.24665+0.044999A-0.01606 7B+0.010397C+0.000163AB+0.000213AC+0.0003755BC-0.000417A2+0.0011B2-0. 00104 C2)}, A is air-temperature\ ?, B is slices thickness/mm, C is air-velocity/ m·s-13 Optimization processing of Codonopsis slices dried in AIJD is: air-temperature is 72 ?, slice thickness is 2 mm, air-velocity is 13 m/s.4. Compared with air-velocity and the unit mass microwave power, the effects of air-temperature and the water content rate at transformation point on the drying time, the unit energy consumption and product quality more apparently. The determined appropriate processing parameters of Codonopsis slices dried by AIJD-MD combined drying is air temperature of 60 ?, wind speed of 12 m/s, the water content rate at transformation point of 40% and unit mass microwave power for 4 w/g.