猕猴桃在冻干-真空微波联合干燥过程中的品质变化与水分分布特征

Quality change and moisture distribution of kiwifruit during FD-MVD

以猕猴桃为原材料,利用冻干-真空微波联合干燥的方式,选取不同的水分转换点(分别为冻干4、6、8、10和12 h),结合猕猴桃在干燥过程中感官品质、复水比、体积密度、孔隙率等,分析猕猴桃片在干燥过程中的干燥特性、孔隙结构和水分分布特征,确定最优水分转换点。研究结果表明,不同水分含量下,猕猴桃片的干燥特性有很大差异,冻干时间越长,猕猴桃片的感官评分越高,复水比越大。冻干时间越长,真空微波时间越短,总的干燥时间越长。微观图片显示,猕猴桃中心和边缘部分的细胞大小有显著差异,影响了水分在中心和边缘部分的迁移。从感官品质的角度来看,冻干12 h是最佳的水分转换点。但从微观结构来看,冻干8 h样品具有最佳的细胞结构。水分转换点的选择不仅受样品质量的影响,还受总干燥时间和干燥能耗的影响。因此,冻干8 h是总干燥时间和质量(感官、微观结构)综合考虑后的最佳水分转换点。

In this study,kiwifruit was used as raw materials,and FD-MVD combined drying method was used to select different moisture conversion points(FD 4 h,FD 6 h,FD 8 h,FD 10 h,FD 12 h).By combing the following characters including sensory quality,rehydration ratio,bulk density,porosity of kiwifruit during drying,with the drying characteristics,pore structure and moisture distribution characteristics of kiwifruit slices during the drying process,the optimal moisture transfer point was determined.The results showed that the drying characteristics of kiwifruit slices varied greatly under different moisture levels.The sensory score and rehydration ratio increased with the increase of the FD time.Moreover,the MVD time decreased with the increase of the FD phase time,on the contrary,the total drying time increased.And the results of the micrographs indicated that the cell sizes of the central and peripheral parts of the kiwifruit were significantly different,which caused the different conversion of moisture in the central and peripheral parts.So,FD 12 h was the optimal moisture conversion point based on the sensory quality analysis.While,if the microstructure was considered as the prefer condition,the FD 8 h sample had the best cell structure.The choice of moisture conversion point was not only affected by the quality of the sample,but also by drying time and drying energy consumption.Therefore,FD 8 h was the optimal moisture conversion point when total drying time and quality(sensory,microstructure)were considered.