为了克服单一干燥造成的品质缺陷,提出了一种新型的组合干燥方式,以改善产品的外观品质和复水特性。以甘蓝为研究对象,主要探讨了组合干燥过程中热风温度、干燥转换点的物料含水率、微波强度、渗透处理对干燥特性的影响;并以成品色泽、复水比、Vc保留率为指标,对不同干燥方式获得的产品性能进行了比较。研究获得的组合干燥工艺参数为:70℃热风干燥至物料含水率60%,2.5 W/g微波强度下干燥至40%含水率,25℃下以2.8 g/mL料液比向半干产品中加入28%葡萄糖和15%NaCl混合渗透液处理15 min,最后70℃二次热风干燥至成品。产品的水分活度为0.466,含水量为16.34%,复水比为8.71,Vc保留率为31.05%。结果显示,组合干燥方式干燥速率快,能耗低,产品含有高水分含量、低水分活度,产品品质与真空冷冻干燥的产品相近,是一种工业化生产果蔬干制品的新方法。

In order to overcome the quality defects created in a single drying process,a novel combination drying process was introduced to improve the appearance and rehydration characteristics of the products.Taking the cabbage as the object,the effects of air temperature,the moisture content of materials conversion point,the microwave intensity,the osmotic treatment on the properties of products during the combination drying process were studied.The products obtained by different drying methods were compared in color,rehydration ratio and Vc retention rate.The optimized combination drying process was drying the cabbages with 70℃ hot air till their moisture content reached 60%,then dehydrating them with microwave intensity of 2.5 W/g till the moisture content reached 40%,followed by adding 28% glucose and 15% NaCl mixture penetration of liquid by 2.8 g/mL solid-liquid ratio and keeping for 15 min in 25℃,finally drying with 70℃ hot-air secondly to get the final products.The water activity of the end products was 0.466,the water content was 16.34%,the rehydrate ratio was 8.71,and Vc retention rate was 31.05%.The results showed that the combination dehydration was fast with low energy consumption,and by which the products with high moisture content and low water activity were obtained.The quality of the products was close to the vacuum freeze-drying ones,and it could be a new way to dry fruits and vegetables in industrial scale.