The diversity of cultivars and variation in phytochemical components pose a great threat to the security of foods that contain walnut. The nutrient values of walnut are stipulated according to phytochemical components, which are driven by internal and external factors associated with fruit growth. The objective of this work was to investigate the effects of cultivar and climate zone on the phytochemical components of walnuts. First, differences and relationships of phytochemical components in eleven walnut cultivars harvested from northeastern China were analyzed. Almost all individual phytochemical components among cultivars showed significant differences (p < .05). The results were submitted to correspondence analysis followed by matrix transformation and factor analysis. Fatty acids, amino acids, and minerals (Ca, Na, Fe, Cu, P, and Zn) for the identification and discrimination of eleven walnut cultivars were authenticated. Furthermore, based on essential microelements, essential amino acids, unsaturated fatty acids, and antioxidants, the walnut cultivars realized the precision position in food application. Finally, we confirmed the effects of climate zones on the phytochemical components of walnuts, with variations up to 142%. The climatic factors precipitation and temperature influenced the formation and accumulation of monounsaturated fatty acids, tocopherols, and most minerals. The findings will open promising perspectives for oriented cultivation of walnuts and future application in the food industry.

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.