INFLUENCE OF THE NITROGEN / LIPIDS RATIO OF MUSTS ON THE REVELATION OF AROMATIC COMPOUNDS IN SAUVIGNON BLANC WINE
Production of volatile compounds by yeast is known to be modulated by must nitrogen. Nevertheless, various parameter of must quality have an impact on yeast fermentation. In this study we propose to evaluate the impact of nitrogen / lipids balance on a Sauvignon Blanc grape juice (Val de Loire).
Must was prepared from the same grapes at pilot scale. Three modalities were carried out: direct pressing, direct pressing with a pre-fermentation cold stabulation and pellicular maceration before pressing. Each juice had been clarified with and without pectolytic enzymes and spiked with different levels of grape solids and diammonium phosphate. The purpose of this experiment plan was to create four modalities with different nitrogen / lipids balances. These musts were fermented in laboratory normalized conditions. In addition of oenological analysis, free fatty acid and sterol were quantified in grape juices. After fermentation, varietal thiols, ethyl esters, higher alcohols and their acetates have been quantified.
Results showed that the nitrogen / lipids balance of grape must affect the concentration of aromatic compounds in wine, especially on the bioconversion of higher alcohols and 3-sulfanylhexanol into their acetates. Nitrogen supplementation was thus confirmed as having a positive effect on the yeast to ester acetates production. However, for the same level of nitrogen, lipids concentration may modulate ester acetates. More generally, a positive correlation has been observed between the nitrogen / lipids ratio and quantity of ester acetates in wine. Linear relation appeared between this nitrogen / lipids ratio and acetates / higher alcohols ratio.
Consequently, the nitrogen / lipids ratio seems to be a useful indicator for the winemaker to better control the desired aroma balance in white wines.
Issue: OENO Macrowine 2023
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white must, nitrogen, lipids, esters