Impact Odorants Contributing to the Fungus Type Aroma from Grape Berries Contaminated by Powdery Mildew (Uncinula necator); Incidence of Enzymatic Activities of the Yeast Saccharomyces cerevisiae

Abstract

Powdery mildew due to the fungus Uncinula necator is an important disease for the vineyard. The development of the fungus at the surface of the berries leads to the occurrence of a very characteristic and sometimes intense mushroom-type odor cited as an important default for grapes quality. Gas chromatography/olfactometry, gas chromatography, and multidimensional gas chromatogaphy/mass spectrometry techniques were used to investigate the most important odorants of grapes diseased by powdery mildew. Among 22 odorants detected, strongly odorant compounds were identified or tentatively identified in purified extracts obtained from grapes diseased by powdery mildew. Aroma extraction dilution analysis (AEDA) analysis revealed that 1-octen-3-one (mushroom odor), (Z)-1,5-octadien-3-one (geranium-leaf odor), and an unidentified odorous zone (fishy-mushroom like odor) were the most potent volatiles of the diseased grapes. In the presence of nonproliferating Saccharomyces cerevisiae yeast cells, and consequently during alcoholic fermentation, the enzymatic reduction of 1-octen-3-one and (Z)-1,5-octadien-3-one to much less odorant compounds, namely 3-octanone and (Z)-5-octen-3-one, was shown. Those results explain to some extent the disappearance of the fungal aroma specific to powdery mildew grapes during alcoholic fermentation.

Effect of yeast strain on aroma compounds in Cabernet franc icewines

“…3-Octanone contributes a mushroom-like aroma to wines. It is metabolized from Uncinula necator on powdery mildew-affected grapes (Darriet et al, 2002). U. necator produces 1-octen-3-one, which is metabolized during fermentation to 3-octanone, which has a lower OAV.…”

“…Commercial yeasts are normally utilized to optimize Cabrera et al (1988). c Darriet et al (2002). d Genovese et al (2007).…”

Isolation and identification of two strains of pathogenic bacteria and their effects on the volatile metabolites of Gracilariopsis lemaneiformis (Rhodophyta)

“…The development of the fungus leads to the occurrence of a very characteristic and sometimes intense mushroom-type odor for grapes. 1-Octen-3-one and 1,5-octadien-3-one are the most potent volatiles of the powdery mildew diseased grapes by (Darriet et al 2002).…”

Review of the role and methodology of high resolution approaches in aroma analysis

“…The presence of g-nonalactone, b-damascenone, and 3-methyl-2,4-nonanedione was identified by MDGC-O/MS which produces a characteristic prune aroma of prematurely aged red wines [60]. By applying similar assays, 1-octen-3-one and (Z)-1,5-octadien-3-one exhibit the most potent volatiles of the diseased grapes by powdery mildew [61]. Pons et al Fig.…”