| Xianggu mushroom(Lentinus edodes (Berk.)sing), belongs to Basidiomycota, Hymenomycetes, Aganicales, Tricholomataceae, Lentinus, which has rich nutrition and curative effects. Microwave vacuum drying technology was used in the process of Xianggu mushroom drying in this paper. The microwave vacuum drying characteristics and the rule of quality changes for Xianggu mushroom were studied, and kinetic models of microwave vacuum drying were established correspondingly to search optimal drying technology for Xianggu mushroom. Meanwhile, influence of different drying technologies on quality characteristics was investigated. The purpose of all above was to provide an important recommendation for practical industrialization of Xianggu mushroom by microwave vacuum drying.1. The microwave vacuum equipment was used to research drying characteristics of Xianggu mushrooms. Effects of microwave power , vacuum degree and loadage on the drying rate were also investigated, from which the rule of water changes during the process of microwave vacuum drying was obtained. And the drying process was divided into three stages that were accelerated phase, conatant-speed phase and decelerated phase. During the drying, the higher the microwave power, the higher the vacuum drgree and the less loadage was, the more frequent the dehydrating rate and the shorter the requirde time was.2. According to the drying characteristics of microwave vacuum drying, the drying kinetics model for Xianggu mushroom was established. The drying kinetics model agreed with Page equation MR = e-rt N, where r = e -2.4418 -0.0062X1+ 0.0002X2 + 0.5173X 3 , N = 0.9500 + 0.0004X1-0.0020X2 + 0.1533X3. It was proved that predicted datas were nearly accordant to experimental datas ,and this model could be used to describe the change of moisture of Xianggu mushroom during the processes of microwave vacuum drying.3. The influences on the content of total free amino acids, content of polysacchardes and content of vitamin C during microwave vacuum drying were studied.⑴The content of total free amino acids climbed up first and then decline with the increase of microwave power; the content of total free amino acids increased with the improving of vacuum drgree and loadage.⑵The retention rate of polysacchardes decreased with the microwave power rising , and increased when the vacuum drgree was rising. The retention rate of polysacchardes climbed up first and then decline with the increase of loadage.⑶The retention rate of vitaminC decreased with the microwave power and the loadage rising while increased with the vacuum drgree rising.4. The optimal technology was obtained by twice regression orthogonal experiment,with the parameters of microwave power ,vacuum degree and loadage and the indicators of sensory quality, polysacchardes and dryingtime, included vacuum degree of -90kPa and the optimal technology was showed as follows: microwave power was 2650W, and loadage was 171g.5. Effects of four drying technologies,including hot-air drying, microwave drying, vacuum drying and microwave vacuum drying, on the shrinkage, rehydration rate, polysacchardes content, total free amino acids, vitaminC content, sensory quality, tissue structure and flavor compounds were investigated respectively. The results showed that:⑴the shrinking percentage of hot-air drying was the highest, the second one was microwave vacuum drying, the lowest was vacuum drying.⑵Microwave vacuum drying had the highest rehydration rate, the second was vacuum drying, the third was hot-air drying and the lowest was microwave drying.⑶The retention rate polysacchardes of microwave vacuum drying was the highest and the lowest was microwave drying. The content of polysacchardes of hot-air drying and vacuum drying were slosed.⑷The sensory evalution of microwave vacuum drying got the highest score, and the second was , hot-air drying and vacuum drying, microwave drying got the lowest score.⑸Obvious and shrinkage happened to Xianggu mushroom after hot-air drying and vacuum drying. Whereas those dried by microwave drying and microwave vacuum drying could keep original tissue structure better.⑹The volatile component of Xianggu mushroom was analyzed by GC-MS, which indicated that the main aromatic components of Xianggu mushroom were sulfocompound, alcohol, aldehyde, acid, ester, alkane and olefin. These compounds played an important part in Flavour of mushroom.The conclusion can be obtained from synthetical analysis: microwave vacuum drying was the best technology among these four technologies for drying Xianggu mushroom.
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