A <i>Basidiomycete Fungus</i> Responsible for Fresh Mushroom Off-Flavour in Wines: <i>Crustomyces subabruptus</i>, (Bourdot & Galzin) Jülich 1978

Abstract

Grape rot can cause organoleptic deviations in wines, including the aroma of fresh mushrooms; one of the molecules responsible for this is 1-octen-3-one. The bunches affected by this defect are often contaminated by Botrytis cinerea; however, they may also contain a whitish mycelium that cannot be attributed to B. cinerea. This additional fungal growth is the subject of this study. Several isolations of this fungus were carried out on grape bunches from different vineyards in the French Alsace and Champagne regions using a culture medium containing an anti-Botrytis fungicide (Boscalid). The sequencing of the ITS regions showed that most isolations corresponded to Crustomyces subabruptus (Bourdot &amp; Galzin; Jülich 1978), an endophyte basidiomycete. Contamination tests carried out on bunches and grape juice with this fungus confirmed its responsibility for the appearance of fresh mushroom defects in wines, and showed that it has the capacity to produce large quantities of 1-octen-3-one in a wet and warm environment. The results of this study suggest that this basidiomycete is responsible for fresh mushroom aromas in wines.

Identification of a Glycosylated Fraction Involved in Mushroom Off-Flavors in Grapes: Influence of Gray Rot, Powdery Mildew and Crustomyces subabruptus

“…In order not to depend on climatic conditions in the vineyard, a contamination model based on several years of research has been designed [ 14 ]. Crustomyces subabruptus , a fungus initially isolated in the Alsace wine region, was also found in Champagne vineyards in 2014 (strain CIVC 02RE14).…”

“…Crustomyces subabruptus , a fungus initially isolated in the Alsace wine region, was also found in Champagne vineyards in 2014 (strain CIVC 02RE14). This fungus, which belongs to the Cystostereaceae family, grows inside grape bunches and is able to impart a fresh mushroom off-flavor by producing 1-octen-3-one to wines from a frozen must of healthy grapes [ 14 ]. This contamination protocol resulted, in a systematic and reproducible way, in a wine with fresh mushroom aromas and constituted the starting point for this study.…”

“…First, the aim was to verify the direct release of C8 molecules with fresh mushroom off-flavors in musts resulting from the contamination model [ 14 , 36 ]. For this purpose, a mixture of pure compounds (1-octen-3-one, 3-octanol, 1-octen-3-ol and also 4-nonanol, which was the chosen internal standard) was analyzed in GC-MS (Full Scan detection) to identify the retention times and the characteristic specific ions ( m/z ).…”

“…Sulfites were added at 3.5 g/hL to batch B, while batch A was kept sulfite-free. After temperature-controlled settling (15 °C, 12 h), the sulfite-free must (A) was contaminated with Crustomyces subabruptus according to Meistermann et al’s protocol [ 14 ]. The contaminated must was then diluted to 1/100 with the sulfited must (B) and stored at −20 °C before experiments.…”

“…In the case of musts affected by Botrytis cinerea , the associated Fiano wines contain a concentration of 1-octen-3-ol that increases with the percentage of rotten grapes [ 13 ]. Recently, it was demonstrated that Crustomyces subabruptus was able to release 1-octen-3-one in both contaminated musts and wines under laboratory conditions [ 14 ].…”