A novel microwave pretreated hot air drying (PMt-HD) process for improving drying efficiency and drying quality of Z. bungeanum

The traditional drying method of Fresh Z. bungeanum has the problems of long drying time and serious loss of nutrients, which seriously restricts its efficient and high-value utilization. This study utilized a self-developed penetrating microwave infrared hot air rolling bed dryer (PMIHRBD) to optimize the drying process and compare microwave hot air drying, microwave pretreated hot-air drying (PM t -HD), and freeze drying with hot air drying (HD). The results showed that the drying time of PM 10 -HD was 48 % shorter than that of HD, and the contents of TFC, TPC and TAC were increased by 17.6 %, 23.7 % and 20.7 %, the yield of essential oil was increased by 59.6 %, and the antioxidant activity was significantly enhanced. According to the identification of VOCs, hydrocarbons, esters and alcohols played a major role in the formation of Z. bungeanum odor, and HD samples had similar characteristics to PM 10 -HD samples. For flavor, PM 10 -HD showed a higher five-flavor richness than other drying processes. In summary, PM 10 -HD provided a fast and efficient drying process for harvesting high quality Z. bungeanum .