Fate of grape flavor precursors during storage on yeast lees.

The effect of the addition of a grape flavor precursor extract to a grape juice, before or after fermentation with three different Saccharomyces cerevisiae yeast strains, on the evolution of the wine aroma composition during a 9-month aging period on yeast lees has been studied. Wine aroma compounds were determined by gas chromatography-mass spectrometry after alcoholic fermentation and after 3 and 9 months of storage. The aging of wine on lees caused important changes in the aroma profiles of wines, making the concentrations of three terpenes, norisoprenoids (except beta-damascenone and beta-ionone), 4-allyl-2,6-dimethoxyphenol, ethyl vanillate, syringaldehyde, and ethyl cinnamate increase, whereas the concentrations of most of the rest of compounds tended to decrease. Lees are responsible for the observed increasing trends, except for linalool and alpha-terpineol, and also for a large part of the observed decrements. As expected, the addition of precursors brings about an increment in the levels of most terpenes, norisoprenoids, vanillins, and ethyl cinnamate, and it is after an aging time when differences linked to the level of precursors in the must become more evident. The timing of the addition of precursors has a minor influence, except for beta-damascenone, vanillin, and syringaldehyde, for which supplementation after fermentation is more effective. It has also been observed that the precursor fraction makes the levels of vinylphenols decrease. Finally, it has also been found that lees from different yeast strains may have a slightly different abilities to release volatile compounds derived from precursors.