Development and optimization of the new ultrasonic-infrared-vacuum dryer in drying Kelussia odoratissima and its comparison with conventional methods

Among the post-harvest processing of medicinal plants, drying is an important and influential process. Given the numerous applications of medicinal plants, especially Kelussia odoratissima, in the food and pharmaceutical industries, the aim of this study was to compare the effects of the ultrasound-infrared radiation-vacuum method with conventional drying methods on the drying time, the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity of K. odoratissima. ANOVA result showed that the effects of drying methods, drying temperature and their interaction effect on phenolic, flavonoid and antioxidant content were significant at 1% probability level. In the ultrasound-IR-vacuum method, by increasing temperature from 40 °C to 80 °C, the TFC increased by 35%. The highest antioxidant capacity was obtained for dry shade treatment, followed by dry sun treatment and three temperatures, i.e., 40 °C, 60 °C and 80 °C, in the combined method. The proposed optimal temperatures for the hot air, IR, and ultrasonic drying, were 63 °C, 66 °C and 71 °C, respectivel