Macrowine 2021
IVES 9 IVES Conference Series 9 First identification of a glycosylated fraction involved in mushroom-off-flavor in grapes: influence of B. cinerea, powdery mildew and C. subabruptus

First identification of a glycosylated fraction involved in mushroom-off-flavor in grapes: influence of B. cinerea, powdery mildew and C. subabruptus

Abstract

An organoleptic defect, called fresh mushrooms off-flavor, appeared in wines and spirits since the 2000’s. Numerous researches demonstrated that octen-3-one, octan-3-ol and octen-3-ol (C8 compounds) were involved in the mushroom off-flavor in wines (Pallotta et al., 1998), (Darriet et al., 2002). Botrytis cinerea and other moldsplayed a role in the metabolism of such molecules directly on the grapes (La Guerche et al., 2006). Moreover, producers couldn’t detect this off-flavor in must but it appeared only in finished wines and the intensity can vary considerably during ageing of wines. Several biogenesis pathways have been proposed to explain the mushroom off-flavor in foods. In the fungus kingdom, the formation of C8 molecules came from the transformation of linoleic acid under the action of several enzymes (Wurzenberger & Grosch, 1984). Glycosidic precursors of octen-3-ol have been identified in several plants such as recently in soybean (Matsui et al., 2018). However, under oenological conditions, no clear mechanism has been established yet. AIM: So, the aim of this work was to (i) identify glycosidic precursors of C8 compounds and (ii) to evaluate the influence of different rots on the glycosylated fractions of different grape varieties. For this purpose, we studied different grades of rot defined by visual intensity (healthy, 1-5%, 10-15% and 20-25% of rots) of grapes and musts of Meunier, Pinot noir and Chardonnay affected by Botrytis cinerea, Powdery mildew and Crustomyces subabruptus. METHODS: From analytical point of view, glycosylated precursors were extracted on C18 cartridges (Lichlorut RP-18, 500 mg),then cleaved by a beta-glycosidase enzyme (Rapidase Revelation Aroma, 40°C, Overnight) and aglycones were analyzed byGC-MS (FS and SIM mode) as reported by Schneider in 2001. RESULTS: For the first time, we identified a glycosylated fraction able to release fresh mushroom aroma (octen-3-one, octen-3-ol, octan-3-ol) in Meunier and Pinot noir musts. Indeed, contaminated musts of Pinot noir treated by beta glucosidase enzyme released three times more octen-3-one than control. In the samples infected with Powdery mildew, we didn’t observe any production of these glycosides. Botrytis cinerea seemed to decrease the level of octen-3-one glycoside(s) as soon as level contamination reached at least 1%. Finally, a Pinot noir must contaminated by Crustomyces subabruptus involved an increase of the glycosylated fraction responsible for the octen-3-one by 31% in comparison with uncontaminated sample. CONCLUSION: In conclusion, the identification of a glycosylated fraction able to release fresh mushroom aroma compounds opens avenue to better understand the source of this specific taint and constitutes the first step to help winemakers to avoid off-flavor.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Léa Delcros 

MHCS, Comité Champagne, Epernay, France,Teddy GODDET, SPO, Univ Montpellier INRAE, Institut agro, Montpellier, France  Sylvie COLLAS, Comité Champagne, Epernay, France  Marion HERVE, MHCS, Epernay, France  Bruno BLONDIN, SPO, Univ Montpellier INRAE, Institut agro, Montpellier, France  Aurélie ROLAND, SPO, Univ Montpellier, INRAE, Institut agro, Montpellier, France

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Keywords

octen-3-one, octen-3-ol, glycosides, mushroom off-flavor, wine, botrytis cinerea, powdery mildew, crustomyces subabruptus

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Macrowine 2021
IVES 9 IVES Conference Series 9 First identification of a glycosylated fraction involved in mushroom-off-flavor in grapes: influence of B. cinerea, powdery mildew and C. subabruptus

First identification of a glycosylated fraction involved in mushroom-off-flavor in grapes: influence of B. cinerea, powdery mildew and C. subabruptus

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The aim of this study was to evaluate the effects of different soil types on the chemical composition of Mediterranean red wines, through untargeted and targeted 1H-NMR metabolomics. One milliliter of raw wine was analyzed by means of a Bruker Avance II 400 spectrometer operating at 400.15 MHz. The spectra were recorded by applying the NOESYGPPS1D pulse sequency, to achieve water and ethanol signals suppression. No modification of the pH was performed to avoid any chemical alteration of the matrix. The generation of input variables for untargeted analysis was done via bucketing the spectra. The resulting dataset was preprocessed prior to perform unsupervised PCA, by means of MetaboAnalyst web-based tool suite. The identification of compounds for the targeted analysis was performed by comparison to pure compounds spectra by means of SMA plug-in of MNova 14.2.3 software. The dataset containing the concentrations (%) of identified compounds was subjected to one-way analysis of variance (ANOVA) to highlight significant differences among the wines. The untargeted analysis, carried out through the PCA, revealed a clear differentiation among the wines. The fragments of the spectra contributing mostly to the separation were attributed to flavonoids, aroma compounds and amino acids. The targeted analysis leaded to the identification of 68 compounds, whose concentrations were significant different among the wines. The results were related to soils physical-chemical analysis and showed that: 1) high concentrations of flavan-3-ols and flavonols are correlated with high clay content in soils; 2) high concentrations of anthocyanins, amino acids, and aroma compounds are correlated with neutral and moderately alkaline soil pH; 3) low concentrations of flavonoids and aroma compounds are correlated with high soil organic matter content and acidic pH. The 1H-NMR metabolomic analysis proved to be an excellent tool to discriminate between wines originating from grapes grown on different soil types and revealed that soils in the Mediterranean area exert a strong impact on the chemical composition of the wines.