Effects of Walnut kernel pellicle on the Storage Quality and Stability of Walnut Oil During Storage

To explore the effects of walnut kernel pellicle on the oxidative stability and storage quality of walnut oil during storage, this study took walnut oil with pellicle (DPM) and walnut oil without pellicle (QPM) as the research objects. A 48-week ambient temperature storage experiment was conducted to systematically analyze the temporal changes in sensory quality, peroxide value (POV), acid value (AV), total antioxidant capacity (TAC), fatty acid composition, and volatile organic compounds (VOCs) of the two types of walnut oil, thereby investigating the impact of walnut kernel pellicle on the quality and stability of walnut oil at different storage stages. The results showed that during storage, the increase rates of POV and AV in QPM were significantly higher than those in DPM (P<0.05), and the sensory score of QPM decreased more rapidly, whereas the TAC of DPM remained higher than that of QPM throughout the storage period. For both oils, the relative content of saturated fatty acids increased while that of unsaturated fatty acids decreased, with more obvious increases in stearic acid content and decreases in cis-9-oleic acid content observed in QPM. After 32 weeks of storage, the sensory evaluation, POV, and AV of DPM and QPM exhibited similar change trends. Moreover, the TAC of both samples decreased significantly after 16 weeks of storage. The number of VOC species increased from 40 at the initial storage stage to 46 at 48 weeks, with furan compounds newly detected. A total of 26 key VOCs were screened out based on the variable importance in projection (VIP) values from partial least squares-discriminant analysis (PLS-DA).Principal component analysis (PCA) results indicated that the differences in VOCs among samples at the same storage stage were small, showing similarities in principal components. With the extension of storage duration, the difference in VOCs between DPM and QPM gradually narrowed. Correlation analysis revealed that DPM and QPM were significantly different in VOCs, sensory evaluation and fatty acid correlation（P<0.01）. The results showed that the walnut oil prepared by retaining walnut kernel coat delayed its own oxidative deterioration and increased its storage stability within a certain storage period, which provided a scientific basis for optimizing the preparation and storage conditions of walnut oil.