title: 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.
authors: Faculté d'OEnologie, Université Victor Segalen Bordeaux 2, 351 cours de la Libération, 33405 Talence Cedex, France. philippe.darriet@oenologie.u-bordeaux2.fr
authors: Philippe
authors: P
authors: Darriet
authors: Monique
authors: M
authors: Pons
authors: Robert
authors: R
authors: Henry
authors: Olivier
authors: O
authors: Dumont
authors: Vincent
authors: V
authors: Findeling
authors: Philippe
authors: P
authors: Cartolaro
authors: Agnès
authors: A
authors: Calonnec
authors: Denis
authors: D
authors: Dubourdieu
mesh_terms: D001203:Ascomycota / Q000737:chemistry* / Q000378:metabolism; D002849:Chromatography, Gas; D005516:Food Microbiology; D008401:Gas Chromatography-Mass Spectrometry; D007659:Ketones / Q000032:analysis; D009812:Odorants; D011786:Quality Control; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D012903:Smell; D027843:Vitis / Q000737:chemistry / Q000382:microbiology*; D014835:Volatilization
chemical_list: D007659:Ketones; C113805:1-octen-3-one