Preparation high quality camellia oil by combining ultrasound pre-treatment and microwave as drying method: Interactive effect on drying kinetics, metabolite profile and antioxidant ability

This study systematically investigates the effects of different drying methods—Hot Air Drying (HAD), Microwave Drying (MWD), and Ultrasound-Microwave Combined Drying (UMWD)—on the drying kinetics, total phenolic content (TPC), antioxidant activity, and metabolome of Camellia oils (COs). UMWD significantly reduced drying time and increased TPC by 102.20 % and 395.94 % compared to MWD and HAD, respectively. The antioxidant capacity, as measured by FRAP, DPPH, and ABTS assays, was enhanced to 8.51, 11.35, and 37.68 µg VC/mL under UMWD conditions, showing marked improvements over MWD and HAD. Metabolomic analysis identified 1,350 metabolites, with 447 differential metabolites specific to UMWD. A total of 47 antioxidant-related metabolites (ACCMs) were identified, most of which exhibited up to a 10-fold increase in UMWD/HAD comparisons. These findings demonstrate that UMWD effectively enhances both the bioactive components and antioxidant capacity of COs, making a significant contribution to the preparation of high-quality camellia oil. Additionally, the study offers new insights into how ultrasound-assisted drying methods can enhance the bioactive components of food products.