Analysis of drying properties and vacuum-impregnated qualities of edamame (Glycine max (L.) Merrill)

To develop a novel dehydrated edamame leisure food, the best edamame from different drying processes was selected to impregnate by different solutions in a vacuum. Microwave drying (MD), pulse-spouted microwave vacuum drying (MVD), vacuum infrared drying (VID), and hot air-drying (AD) were researched, when the drying quality of edamame samples was analyzed for microstructure, color, texture, and flavor. MVD product was found to be the most suitable sample for impregnation. Vacuum impregnation was undertaken with this dried edamame at different impregnated solutions (sucrose, trehalose, and maltose solutions). Through magnetic resonance imaging (MRI) analysis, it was found that three solutions were uniformly distributed in cotyledons after vacuum impregnation. There are some differences in flavor among the impregnated samples in electronic nose. The water state (bound, immobilized and free) in the samples was analyzed during MVD by low-field nuclear magnetic resonance (NMR). The water mobility was found strong in the samples in most of the drying process, and with the progression, the free water gradually disappeared. In the impregnated edamame, the water mobility was much weaker, thus the impregnated edamame can be assumed more suitable for snacks with a longer shelf-life.