Effects of pre-cutting treatments and combination drying with different orders on drying characteristics and physicochemical properties of Lentinula edodes.

BACKGROUND: Combination drying is recognized as an energy-efficient method utilized for dry product processing, and proper order of combination is a critical factor determining the effectiveness of the technique. In this study, hot air drying (HD), vacuum freeze-drying (VFD), and combination drying with different orders (HD-VFD and VFD-HD) are performed on whole Lentinula edodes and pre-cut (half-cut and quarter-cut) L. edodes. The effects of various cutting and drying approaches on drying characteristics, physicochemical properties, and microstructures of dried L. edodes were investigated. RESULTS: The longest processing time required to dry the whole L. edodes by VFD was 25 h. In contrast, the pre-cutting treatment and combination drying certainly shortened the drying time. Compared with HD, use of VFD-HD and VFD significantly decreased the shrinkage ratio, hardness, and discoloration of dried products but increased the rehydration capacity, nutrient retention, and porous microstructure. Interestingly, switching the order of combination drying provoked entirely different drying effects. Specifically, HD-VFD triggered negative effects on the shrinkage and color of dried mushrooms, and its appearance color was similar to HD-treated samples. Moreover, pre-cutting dramatically enhanced the protein content of HD-treated mushrooms, and the quarter-cut samples obtained the highest level (21.69 g kg-1 dry basis) among the three types of cutting. CONCLUSIONS: The dried L. edodes processed through pre-cutting and combination drying (VFD-HD) have optimal industrial quality, accompanied by shorter processing time. © 2020 Society of Chemical Industry.