Effect of free fatty acids and lipolysis on Sauvignon Blanc fermentation

Background and AimsThe volatile thiols, such as 3-mercaptohexanol, 3-mercaptohexyl acetate and 4-mercapto-4-methylpentan-2-one, are major aroma compounds responsible for the distinctive tropical notes (passionfruit and grapefruit) in New Zealand Sauvignon Blanc wines. Previously, it was observed that traces of linoleic acid in grape juice can significantly affect the development of these volatile thiols and other aroma compounds in wine. Here, we examined the effect of the fatty acids commonly found in Sauvignon Blanc grape juice as well as juice lipid lipolysis on the development of aroma compounds in the resulting wines. Methods and ResultsExperiments were performed to increase the total free fatty acid concentration in grape juice through juice treatment with acidic lipase from Aspergillus niger and through co-cultured fermentations with non-Saccharomyces lipase-secreting yeasts. We observed a significant reduction in the production of 3-mercaptohexyl acetate in fermented wines upon supplementation with linoleic acid and lipase. Supplementation with lipase increased the concentration of 3-mercaptohexanol and all ethyl esters detected, while reducing the development of acetate esters. Co-cultured fermentations also affected the development of many classes of aroma compounds. ConclusionsThis study demonstrated that the aroma profile of wines could be effectively manipulated by altering the amount of free unsaturated fatty acids in grape juice through lipolytic enzyme supplementation or co-fermentation with non-Saccharomyces lipolytic yeast species. Significance of the StudyThe key findings of this study may lead to new winemaking strategies through the manipulation of the lipid component of grape juice.