Comprehensive lipid profiling of grape musts: impact of static settling

Abstract

Lipids are crucial in alcoholic fermentation, influencing yeast metabolism by providing nutrients and modulating membrane composition [1]. They also serve as precursors to aromatic compounds shaping wine sensory profiles [2]. While sterols and unsaturated fatty acids have been extensively studied, the overall lipid composition in grape musts remains poorly understood. Many lipid families, including phospholipids, sphingolipids, and glycolipids, have been largely overlooked. This study aims to provide a comprehensive lipid profile by identifying as many species as possible, beyond the commonly studied sterols and fatty acids.

Clarification, a widespread winemaking process, significantly reduces lipid availability, potentially leading to slow or stuck fermentations and undesirable aromas [4-6]. This study examines white grape musts from eight varieties and the impact of static settling on lipid composition. Initially, untargeted LC-MS QToF was used to capture a broad lipid spectrum, guiding targeted quantification methods. Free fatty acids, total fatty acids, and sterols were quantified via GC-MS, while phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, steryl esters, glycerolipids, and ceramides were analyzed by LC-MS.

For the first time in grape must analysis, an untargeted LC-MS QToF approach enabled the detection of 562 lipid compounds, 112 of which were confirmed as sphingolipids, fatty acids, phospholipids, glycerolipids, and sterols. Some lipid subclasses, such as (lyso)phosphatidylethanolamines, (lyso)phosphatidylinositols, and steryl esters, had never been reported in grape musts. Targeted quantification by GC-MS and LC-MS identified 375 lipids across nine subclasses, with 297 displaying significant differences (ANOVA α=0.05). Clarification significantly affected lipid concentrations, impacting 73% of detected species (Kruskal-Wallis α=0.05), particularly sterols, fatty acids, and phospholipids—key molecules for yeast metabolism.

These findings underscore the importance of studying the full complexity of lipid composition in grape musts and suggest that revising clarification practices could help preserve essential lipids, thereby improving fermentation efficiency and wine quality. Overall, this study provides new insights into the lipid composition of grape musts and the nutritional challenges yeast may face during fermentation.

References

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[6] Vázquez-Pateiro, I.; Mirás-Avalos, J. M.; Falqué, E. (2022) Molecules, 27 (3), 810.