Microwave pretreatment combined with hot air drying enhances the drying efficiency and quality properties of Fructus Aurantii by altering its microstructure and moisture state distribution

Abstract

As a seasonal herbal medicine with high water content, fresh Fructus Aurantii (Citrus aurantium L.) cannot be efficiently dried using traditional hot-air drying (HAD) alone. This study introduces microwave pretreatment combined with HAD to investigate the effects of microwave pretreatment time (0, 2, 4, 6, and 8 min) on the drying characteristics, microstructure, moisture distribution, and physicochemical quality of F. Aurantii dried with hot air. Microwave pretreatment formed a micropore formation and altered water-state distribution, thereby shortening the drying time of F. Aurantii by 11.11% - 80.56%. Lewis, Page, and Weibull models were established to describe moisture-ratio changes of F. Aurantii with drying time, and all three models were able to satisfactorily predict the moisture changes during the drying process. Microwave pretreatment at 700 W for 6 min significantly enhanced the quality of F. Aurantii, increasing the rehydration ratio, as well as naringin and neohesperidin contents, by 12.65%, 29.17%, and 31.09%, respectively. The optimal appearance was achieved under 700 W for 4 min pretreatment. This study provides valuable insights for further optimization of microwave-assisted HAD processes for F. Aurantii.