The effect of osmosis pretreatment on hot‐air drying and microwave drying characteristics of chili (Capsicum annuum L.) flesh

Summary Chili flesh pretreated with or without osmotic dehydration ( OD ) was dried in the hot‐air drying ( AD ) oven at 50–80 °C or in the microwave drying ( MD ) oven at 60–180 W. Results showed that the samples osmotically treated in mixed solution (10% salt + 50% sucrose) had the best dehydration effect as compared with single salt or sugar solutions. During the drying process, osmotically treated samples had one falling‐rate period and their effective moisture diffusivities ( D eff ) showed a rapidly linear increase with the decrease in moisture content, while directly drying samples showed a three‐phase falling‐rate period and their D eff increased gradually at the initial period and then rapidly at the final period. When the moisture content decreased, the activation energy increased gradually; however, for AD after OD , it decreased. Among all the processes, MD at 60 W after OD presented the largest vitamin C retention rate and the best colour difference, needing less drying time.