Continuous microwave drying of germinated red adzuki bean: Effects of various drying conditions on drying behavior and quality attributes

Abstract

This study investigated the effects of various drying conditions involving microwave power, air velocity, and sample mass on the drying behavior, starch gelatinization properties, and gamma-aminobutyric acid (GABA) content of germinated red adzuki bean (GRAB) under continuous microwave drying. Increasing the microwave power and lowering the sample mass can promote GRAB drying and shorten the total drying duration; improving the air velocity limited the temperature elevation of GRAB to affect water removal to some extent. The drying rate had only the rising- and falling- rate stages throughout the drying process. Microwave drying lowered the gelatinization temperature and enthalpy to facilitate the starch gelatinization of GRAB. The microwave power and sample mass had significant effects on the GABA content of the final dried GRAB. This study may provide guidance for understanding and follow-up improving the continuous microwave drying production of germinated bean products like GRAB. Practical applications GRAB is consumed as a nutritional food source due to its high starch and protein contents, low fat, and rich bioactive ingredients like GABA. Drying processing is a needed step for fresh GRAB to facilitate long-term storage and quality retention. This study evaluated the drying behavior and quality attributes of GRAB in a continuous microwave belt dryer, and the research results have underlying application potential and may provide guidance for microwave drying production of germinated bean products like GRAB.