Experimental Study On Drying Ginseng Process And Device By Microwave Vacuum

The aim of this research was to study on the mechanism of microwave vacuum drying, develop drying device of microwave vacuum with fresh ginseng as the processing material. The effect of technical parameters on drying characteristics in drying process was analyzed, and the drying technology of valuable Chinese traditional medicine such as panax ginseng was optimized. Theoretical and processing directions for drying the valuable Chinese traditional medicine were provided. The research was supported by the special fund of The Ministry of Science and Technology of the People's Republic of China.Panax ginseng dried by the combination technique of heated wind and microwave vacuum was studied. Made use of the advantage of heated wind that the quantity of water could fast declining, the orthogonal experimental design examination has been done by applying three factors and three levels, ANOVA was given by SAS software, the effect of nine groups experiments was different to the variety of color, ginseng saponin Re,Rb1,Rg1, vitamin C and the ability of obtaining water. The optimum processing parameters were found: when the quantity of water was 50%, the vacuum was 0．085MPa, the thickness was 4mm, the dried product was best. The panax ginseng saponin Re=0．152%, 13．6% reduced; Rb1=0．251%, 2．3% reduced; Rg1=0．397%, 5．5% reduced; vitamin C=0．49mg in one gram materiel (no water), 35．5% reduced; the ratio value of obtaining water was 2．12, the time of obtaining water was 5min; the variety of color was△E*ab=5．1965, the color of dried product was well-proportioned, with strong flavor of panax ginseng, the surface was slick, crisp, the degree of distortion was less than1/5 and more 1/10．Panax ginseng dried by other drying methods. Panax ginseng dried by microwave process has been studied. 2mm～4mm slices of panax ginseng was processed under the condition of microwave power of 700W, the best thickness was 3mm. Panax ginseng dried by vacuum process was also studied. 2mm～4mm slices of panax ginseng was processed at 0．05 MPa～0．09MPa of vacuum, the best vacuum was 0．09MPa, the best thickness was 4mm. Panax ginseng dried by heated wind process was studied. The best temperature was 50℃, the best thickness is 3mm. Panax ginseng dried by freeze sublimation process was studied. The best thickness was 3mm.The comparison between different drying methods and microwave vacuum has drying been performed with the processing material of 2mm～4mm slices of panax ginseng. Under the same condition, the time taken of microwave drying was the shortest, reeze sublimation was the longest; the reduction of panax ginseng saponin Re: less than vacuum drying 3．4%, less than microwave drying 35．8%, less than freeze sublimation drying 26．7%, less than heated wind drying 34．7%; the reduction of panax ginseng saponin Rb1: less than vacuum drying 7．8%, less than microwave drying 55．7%, less than freeze sublimation drying 40．1%, less than heated wind drying 31．2%; the reduction of panax ginseng saponin Rg1: less than vacuum drying 41．2%, less than microwave drying 41．2%, less than freeze sublimation drying 37．4%, less than heated wind drying34．7%; the reduction of vitamin C: more than vacuum drying 2．6%, less than microwave drying 11．9%, less than freeze sublimation drying 9．2%, less than heated wind dryingl5．8%; the ratio value of obtaining water was smaller, the time of obtaining water was a little change; the variety of color was large: more than vacuum drying 1．2042, less than microwave drying 6．9955, more than freeze sublimation drying 0．2837, less than heated wind drying 2．2377; the degree of distortion was not better than freeze sublimation drying.So, the product quality of microwave vacuum drying was best. The comparison of freeze sublimation drying methods, the degree of distortion for microwave vacuum drying needs improving.According to the conclusion of examinations, parameters were chosen to design device of microwave vacuum, used columniform syntonic chamber; vacuum≤0．1MPa; special material was used to prevent microwave from leaking, such as the rubber was applied to ensure airproof, and the double airproofing of microwave and vacuum was carried out.