## 1 Introduction  
Lipids are defined as hydrophobic molecules that are soluble in organic solvents and can be classified according to their molecular structure as well hydrolysis products/chemical backbone. Most commonly, lipids are divided into eight categories, namely fatty acids, sterols, glycolipids, glycerophospholipids, polyketides, sphingolipids, phenol lipids and sacchorolipids [1]. Furthermore, lipids can be regarded as simple (sterols, fatty acids, etc.) or complex (glycerophospholipids, glycolipids); the former yields, at most, two products after hydrolysis, and the latter results in three or more products [2, 3]. hydrophobic compounds are found in microorganisms [4, 5], plants [6], and animals [7]. Lipid functions are related to energy storage [8], organelle structure maintenance [9], and enzyme activation or signaling [10]. Furthermore, lipids are an integral part of the plasma membrane, which serves as a semi-impermeable bilayer that ensures compartmentalization and facilitates the transport of metabolites, and other biochemical processes necessary for cellular functioning [11]. Changes in the plasma membrane phospholipid, sterol, and fatty acid content are necessary for cellular viability and survival in stressful and dynamic environmental conditions [12, 13, 14]. In yeast, the synthesis of fatty acids is a complex process mediated by a variety of enzymes with acetyl-CoA as the main building block [15]. Ergosterol is the main sterol produced in yeasts and, similarly to fatty acids, this sterol is synthesized with acetyl-CoA as the main substrate [16]. While the production of saturated fatty acids in the yeast cell can occur in the absence of oxygen, the biosynthesis of unsaturated fatty acids [17] and ergosterol is oxygen dependent [18]. Thus, the presence of unsaturated acids and sterols in the surrounding environment is necessary for yeast growth in oxygen-limiting conditions such as those occurring during the alcoholic fermentation of grape must [19]. In addition to influencing yeast growth, the presence of unsaturated fatty acids and sterols in the plasma membrane is also linked to ethanol stress resistance during vnification [20; 21; 22]. Moreover, these lipids were observed to have an effect on the production of aroma compounds such as ethyl esters, acetate esters, and higher alcohols, which play a key role in wine quality [13; 20; 23]. Therefore, the analysis of free fatty acids and sterols in grape juice provides essential information to understand and predict yeast performance as well as aroma production during fermentation, which allows for a better characterization of the yeast lipid metabolism. The Bligh and Dyer method [24] as well as the Folch method [25] are popular protocols used to extract fatty acids from a variety of matrices using a chloroform:methanol solution. In oenology, modified extraction protocols based on the Folch or Bligh and Dyer methods have been described for the extraction and profiling of fatty acids from Sauvignon Blanc grape juice [26] and red wine [27]. Furthermore, fatty acids could also be extracted from Koshu and Pinot Noir juice samples using methanol, 2,6-di-_tert_-butyl-\(p\)-cresol and formic acid [28]. Free fatty acids and sterols were also extracted from Chardonnay grape musts using ethanol:water [29], but this method requires large sample and solvent volumes. The analysis of yeast-derived fatty acids and sterols is also necessary to evaluate changes in the cell composition as fermentation progresses. Numerous studies focused on the lipid composition of yeasts have been published and the extraction protocols used are also mainly based on the Folch or the Bligh and Dyer methods [30; 31]. However, complex or combined lipids such as phospholipids and steryl esters in yeasts have to be hydrolyzed to liberate free fatty acids or sterols using an acid (such as HCI) or a base (such as KOH). This process can happen either before or after lipid extraction [29; 32; 33; 34].