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

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. Botrytis cinerea and other molds played a role in the metabolism of such molecules directly on the grapes. 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. Glycosidic precursors of octen-3-ol have been identified in several plants such as recently in soybean. However, under oenological conditions, no clear mechanism has been established yet. 

So, the aim of this work was to identify glycosidic precursors of C8 compounds and to evaluate the influence of different rots on the glycosylated fractions of different grape varieties. For this purpose, studies of 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 were carried out.

From analytical point of view, how were the glycosylated precursors extracted and analyzed? Find out how for the first time, a glycosylated fraction able to release fresh mushroom aroma was identified (octen-3-one, octen-3-ol, octan-3-ol). What differences were detected between the samples infected with Powdery mildew, Botrytis cinerea and Crustomyces subabruptus?

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.

Video extract from Macrowine virtual (June 23-30, 2021) ROUND TABLE #3 – Advances in vinification processes, novel compounds and novel reactions