Studies On Technologies Of Microwave Vacuum Combined Air Drying For Kiwifruit Slices

Kiwifruit(Actinidia Actinidia)is of woody vine fruit which is a special kind of berries riching in vitamin C,it has the very high value of nutrition.But the shelf life is short and during the storage process it is easy to soften,loss vitamin C,cause mechanical damage in transition,which lead to accelerate the process of corruption for kiwifruit.Drying is a good choice to solve those problems.In this paper,"Qin Mei" kiwi fruit as raw material,the effects of microwave vacuum-air drying technologies on the qualities for kiwifruit slices was investigated.And the optimum drying process parameters and conditions of microwave vacuum-air drying were determined.The main results were as follows:1.In order to obtain the high-quality dehydrated kiwifruit slices,the drying characteristics and the product qualities of kiwifruit slices dried by air drying(50 ?,60 ?and 70 ?)or microwave vacuum drying(5 W/g,10 W/g and 15 W/g)or combined microwave vacuum with air drying(10 W/g,6 min,than 70 ?)were investigated.The results showed that the effect of different drying methods on shrinkage,rehydration and sensory of dried kiwifruit slices,the drying time,the energy consumption were significantly different.The VC contents,shrinkage and rehydration of products treated by combined drying were slight less than microwave drying,but much better than those of conventionally air drying;The sensory of products treated by combined drying was optimal.2.The drying dynamics characteristics and drying model of thin layer and microwave vacuum drying for kiwifruit slices were investigated and constructed respectively.The effects of the air drying conditions like sample thickness,air temperature and air velocity on drying kinetics of kiwifruit and the effects of microwave vacuum drying conditions like sample thickness,vacuum degree,microwave intensity were investigated.The results showed that air drying and microwave vacuum drying model are consistent with the Page model.3.Microwave vacuum drying-air drying was applied for kiwi slices,and the effects of the microwave intensity,vacuum degree and air temperature on qualities of kiwifruit slice were investigated.The results showed that Microwave power,vacuum degree and air temperature have greatly effection on the qualities of kiwifruit slices and energy consumption.As the microwave intensity increasing,the contents of vitamin C in kiwifruit slices decreased,the content of chlorophyll and the drying energy consumption increased,the rehydration rate increases decreased firstly and then increased with the microwave intensity.As the increasing of vacuum degree,the content of vitamin C in kiwifruit slices,the content of chlorophyll,the rehydration rate,the higher energy consumption of drying all were increased.As the air temperature increased,the contents of vitamin C in kiwifruit slice,rehydration rate,drying to reduce energy consumption were decreased.But chlorophyll content with the air temperature increased firstly and then decreased.4.Response surface methodology was employed to optimize the conditions for microwave-vacuum drying and air-drying of kiwifruit slices aimed at improving the quality of kiwifruit slices product.Comparative drying of kiwifruit slices by three different methods,air-drying,microwave vacuum drying,and microwave-vacuum drying and air-drying were used to confirm the optimum drying condition.The results showed that the optimal combined drying were microwave power of 14.71 W/kg,vacuum degree of 0.08 Mpa,microwave time of 7min,and air-drying of 61.51 ?.Comparative drying of kiwifruit slices by three different methods,By comparison,the quality of product with combined drying significantly better than air drying and microwave drying.