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.

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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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In the present study, a microzoning at 1:10.000 scale is generated from an initial zoning, where the conventional soil map with polytaxic map units is replaced by a new one from digital techniques that disaggregates them. The comparison between the zonings considers a quantitative evaluation of capability for each Homogeneous Terroir Unit by means of the Viticultural Quality Index and its categorization based on its distribution by map. The spatial intersection of both maps gives rise to a confusion matrix in which the flows of class variations after the substitution are assessed.

The results show a five-fold increase in the number of Homogeneous Terroir Units identified and a larger differentiation among them, evidenced by a wider range in the capability index distribution. Both elements are accompanied by an increase in the detection of areas of higher potential within previously undervalued uniform zones.These features are a direct effect of the improvements brought by Digital Soil Mapping techniques and would verify the advantages of their implementation in the Integrated Terroir zoning. Eventually, such new highly detailed terroir units would benefit precision viticulture and sustainable management practices.

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