Effect of Different Drying Technology on Quality of Astragalus Water Extract

To develop the new drying technology for the condensing or dehydration of solvent extract of Chinese Herb Medicine (CHM),drying experiments of water extract of Astragalus were carried out. 4 different techniques,microwave drying,hot-air drying,vacuum drying and freeze-drying,were discussed in this paper. The micro-structure characteristics of samples were characterized by micrograph technique in the dimension of micron and nanometer,and the content of Astragalus polysaccharide (APS) of the samples were tested by ultraviolet spectrophotometer. The result shows that the dehydrated water content from the extract at 1h by microwave drying is almost the same as that at 4h by other 3 drying techniques. The microstructure characteristics of the dried sample by different drying techniques are related to the dehydration mechanism and its quality. The APS content of sample by microwave drying is little more than that by other 3 drying techniques. Therefore,the microwave drying technology can be used for the concentration and dehydration of CHM with the advantage of shortened drying time and better preservation of active ingredients