HOLISTIC APPROXIMATION OF THE INFLUENCE OF SACCHAROMYCES STRAINS ON WINE AROMA PRECURSORS

Abstract

Wine varietal aroma is the result of a mixture of compounds formed or liberated from specific grape-aroma precursors. Their liberation/formation from their specific precursors can occur spontaneously by acid catalyzed rearrangements or hydrolysis or by the action of the yeast enzymatic activities. The influence of yeast during fermentation on the production of these volatile compounds has been widely studied however, the effect of this influence during aging is not fully understood. In order to evaluate these processes several indirect strategies have been used to study aroma precursors although they are not useful to understand the chemistry of the process. Therefore, the deep development of liquid chromatograph-mass spectrometers (LC-MS) during the last years has promoted some direct analysis of aroma precursors to identify them.

The objective of the present work is to study the influence of yeast on the aromatic precursors of wine and how that modulates the wine aroma during aging and its longevity. For that, four different yeasts (three S. cerevisae strains, Lalvin QA23™, Lalvin Sauvy™ and Lalvin Rhône 2056®, and S. kudriavzevii CR89D1) were selected attending to their different abilities to modulate aroma compounds. A must obtained combining 6 different grape varieties was fermented with the 4 strains and wines were aged under anoxia during 12, 24 and 96 hours at 75ºC. After this process volatile compounds of young and aged wines were analyzed by gas chromatography mass spectrometry (GC-MS) and in parallel, the aromatic precursor fraction of must and young wines was characterized using UPLC-QTOF-MS untargeted analysis.

The targeted approach revealed remarkable differences in levels of vinylphenols, some terpenes, polyfunctional mercaptans, esters and some lactones. However, the concentration of norisoprenoid aroma compounds was not influenced by yeast. As it was expected, the metabolomic study revealed notable changes on young wines respect to the grape must, although the effect of yeast on putative glycosidic aroma precursors was marginal. These compounds were more influenced during aging, which supports the relevance of aging for producing varietal aroma derived from glycosidic precursors. This study has also made it possible the putative identification of some glycosidic precursors, which have to be studied to evaluate their relevance on the wine varietal aroma.