Study On The Microwave Vacuum Drying Characteristics And Drying Technology Optimization Of Cabbage

Cabbage is also known as Brassica oleracea var. capitata L., which is rich innutrient with high health value. Dehydrated cabbage is the one of the main dehydratedvegetables for exportation in China. In order to research the characteristics ofmicrowave vacuum drying on cabbage, microwave vacuum drying technology wasapplied in the cabbage drying process in this paper. The impact rules of themicrowave vacuum drying process parameters on cabbage quality characteristics wasanalyzed as well, and the drying process was optimized, which finally help todetermine the parameters of microwave vacuum drying process. The effect of thetempering process on the microwave vacuum drying process was considered and theimpacts of the different drying methods on the cabbage quality characteristics werecompared in this study. The results are as follows:1. The dehydrating characteristics of the cabbage during the drying process wereinvestigated, the results showed that the whole microwave vacuum drying process canbe divided into three drying stages, accelerating phase, constant speed phase anddecelerating phase. After blanching, microwave power and vacuum were increasedwith the reduction of load, which shortened the time for completing the dryingprocess.2. The influences of microwave vacuum drying pretreatment, microwave power,vacuum and load on the rehydrating rate, chlorophyll content, vitamin C content andsoluble sugar content of cabbage were discussed. The results showed the driedcabbage processed by0.25mol/L soda blanching at90℃,45s,presented a relativelyhigher quality. Under the same test condition, the impact of microwave power oncabbage quality indicators was more significant than that of vacuum and load.3. Taking rehydrating rate, the chlorophyll content, the Vitamin C content and thesoluble sugar content as the evaluation indexes, the processing parameters ofmicrowave power, the vacuum and load were optimized by the L9(3~4) orthogonalexperiment. The relatively optimizing processing parameters for microwave vacuum drying of cabbage were determined: the microwave power was3kW, the vacuum was-75kPa, the loading was600g. Finally, the drying quality of cabbage treated by theimproved process was superior compared with microwave drying technology.4. The microwave vacuum-tempering technology of cabbage and the variationrule of moisture content were mainly explored in this study, meanwhile the impact ofdifferent tempering process conditions, including tempering time, initial temperingwet basis moisture content and tempering surroundings humiture on the drying ratewere studied as well. The results indicated that initial tempering wet basis moisturecontent was lower with the longer tempering time, the tempering effect was muchmore apparent with lower ambient humidity, while the tempering effect in theexperiment group of4°C tempering temperature was not as good as temperingtemperature of25°C.5. The influences of three different drying methods, including hot air drying,microwave vacuum drying and microwave vacuum drying with tempering process onrehydrating rate, chlorophyll content, vitamin C content, soluble sugar content,sensory quality and texture structure of cabbage were studied, and the energyconsumption of the three methods were compared as well. The results showed thecomprehensive quality of dried cabbage processed by microwave vacuum dryingtechnology was better, compared with the traditional hot air drying technology.Furthermore, the quality was improved and the energy consumption was lower,combining with the tempering process.