Comprehensive comparative analysis of lipid profile in dried and fresh walnut kernels by UHPLC-Q-Exactive Orbitrap/MS

Lipids are important nutrient components in walnuts. However, there has been a lack of comprehensive analysis of lipid composition in walnuts. Here, UHPLC-Q-Exactive Orbitrap/MS was employed to qualify and quantify the lipid compounds in seven walnut varieties from Xinjiang. A total of 390 lipids were tentatively identified, which were classified into six categories and 30 subcategories. GL and GP were the two most abundant lipids in all walnuts. Compared with fresh walnuts (FW), dried walnuts (DW) showed significantly higher lipids; in the 30 subcategories, DW showed decreases in some MGDG and PC while increases in LPC and MePC, all of which were related to the moisture content of walnuts. Totally, 128 lipids can be used as potential markers to distinguish FW from DW. Besides, the lipid profile varied among different varieties of walnut kernels. These findings may facilitate walnut variety selection and processing based on the characteristic lipids.