Lipid remodeling induced by processing drives flavor formation in walnut oil: Insights into thermal, shear, solvent and moisture effects.

The mechanisms underlying lipid-flavor conversion in vegetable oils mediated by different processing pathways remain unclear. In this study, flavoromics and lipidomics were integrated to systematically characterize the volatile flavor profile, lipid composition, and their interactions in walnut oil produced using nine processing pathways. Furthermore, the influence of thermal, shear, solvent, and moisture effects on lipid remodeling and flavor formation was systematically analyzed. The results identified a total of 211 volatile compounds, including 19 key aroma compounds. Representative compounds included 2,4-Decadienal, Nonanal, Hexanal, 1-Octen-3-one, and Linalool, collectively contributing to the fatty, roasted, green, mushroom-like, and floral aroma characteristics of walnut oil. Lipidomics analysis identified 900 lipid molecules, with TG, DG, PE, and Cer identified as the major responsive lipid subclasses. Representative characteristic lipids from glycerolipids, glycerophospholipids, and sphingolipids, including TG(20:1/18:3/22:1), PE(18:4/18:3), Cer(t18:1/26:0), and Hex1Cer(t16:0/18:2), showed distinct enrichment patterns across different processing pathways. KEGG enrichment analysis revealed that the differential lipids were mainly involved in Glycerolipid metabolism, Glycerophospholipid metabolism, and Sphingolipid metabolism. Correlation analysis further revealed close associations between representative lipid subclasses and key aroma compounds. Overall, thermal, shear, solvent, and moisture effects jointly drove the differentiated formation of walnut oil flavor quality by reshaping the lipid metabolic network. This study provides new insights into the relationships between lipid remodeling and flavor formation under different processing pathways and highlights potential common patterns that may contribute to mechanism-oriented precision optimization of vegetable oil processing.