The characteristics of hot air and vacuum microwave drying were compared using edamame as the raw material, and an optimized combination drying process was then established thereof so as to achieve increased drying rate and enhanced product quality. Edamame was subjected to 70 degrees C hot air drying for 20 min, and then microwave dried at power intensity 9.33 W/g for 15 min under -95 kPa (gauge pressure). The optimized combination drying process exhibited significantly shortened drying time as compared with conventional hot air drying, and greatly decreased mass loads on the vacuum microwave dryer. (c) 2005 Elsevier Ltd. All rights reserved.