Comprehensive characterization of physicochemical quality and volatile organic compounds of walnut oil under different treatment conditions based on HS-GC-IMS and chemometrics

• Walnut oil quality and VOCs were affected by varying treatments. • HS-GC-IMS revealed VOC profile differences in walnut oil under varying treatments. • HS-GC-IMS and chemometrics revealed 20 key VOCs with VIP>1. • Significant correlations were confirmed among quality, fatty acids, and VOCs. This study aimed to combine headspace gas chromatography ion mobility spectrometry (HS-GC-IMS) with chemometric analysis to investigate the differences in physicochemical characteristics and volatile organic compounds (VOCs) among walnut oils obtained through three different processing methods: hydraulic cold pressing of walnut kernels with the seed coat (DPM), hydraulic cold pressing of walnut kernels without the seed coat (QPM), and supercritical CO 2 extraction of walnut meal left after hydraulic pressing of walnut kernels without seed coat (QPC). A comprehensive analysis of the physicochemical characteristics, VOCs, and fatty acid composition of the walnut oils was conducted, accompanied by correlation analysis. The results indicate that QPC exhibited the highest peroxide value (POV) at 0.16 g/100 g. Concurrently, QPC acid value (AV) was significantly higher than that of DPM and QPM by 0.24 mg/g and 0.26 mg/g, respectively ( p < 0.05). The ratio of polyunsaturated fatty acid (PUFA) to monounsaturated fatty acid (MUFA) was 7.75, which is consistent with the characteristic high-PUFA profile of walnut oil. A total of 50 volatile organic compounds (VOCs), including aldehydes, alcohols, ketones, esters, acids, and terpenes, were identified using HS-GC-IMS technology. Partial Least Squares Discriminant Analysis (PLS-DA) identified 20 characteristic VOCs (VIP>1). The study further revealed significant correlations among the physicochemical quality of walnut oil, its fatty acid composition, and these key VOCs. This research provides essential theoretical insights for assessing how different processing conditions influence nutrient retention and VOCs profiles in walnut oil.