Origin of fresh mushroom off-flavor in wine Sourced from the research article: “A Basidiomycete fungus responsible for fresh mushroom off-flavour in wines: Crustomyces subabruptus, (Bourdot & Galzin) Jülich, 1978” (OENO One, 2021). This is a translation of an article originally written in French.

Fresh mushroom flavor in wine is generally considered a fault. The fungus responsible for this organoleptic defect, Crustomyces subabruptus, has recently been isolated. The main compound involved is 1-octen-3-one, which is perceptible in white wines at concentrations above 40 ng/L.
Introduction
Fresh mushroom off-flavor is characterized by an odor typical of the common mushroom. It is sometimes accompanied by similar odors, such as undergrowth or humus, but without vegetal or moldy notes. This odor is unacceptable in dry wines and sparkling wines. In high-alcohol wines it may blend in with the underlying aromatic complexity. Undergrowth aroma is one of the typical descriptors of some Pinot Gris wines from Alsace. The problem appeared in Alsace in the 1990s. It strongly impacted the 2006 vintage due to the particularly unfavorable climatic conditions that year
Compounds responsible
Several compounds have a fresh mushroom odor. Three of them have been identified in affected wines. 1-octen-3-ol has a perception threshold of approximately 40 µg/L in white wine. The concentrations measured in faulty wines rarely exceed this value. It does not contribute to the fault. The two other compounds, 1-octen-3-one and 1-nonen-3-one, have a much lower perception threshold (40 ng/L and 20 ng/L respectively in white wine) and can be found in wine at concentrations above these values. The former is found much more frequently, however, and it has been shown that the intensity of fresh mushroom off-flavor is correlated to the 1-octen-3-one concentration in the wine
Microorganism responsible
A basidiomycete capable of producing large quantities of 1-octen-3-one has been isolated from grapes with fresh mushroom off-flavor in work carried out by the IFV, CIVA and CIVC
Figure 1. Pinot Gris with botrytis bunch rot and the white mycelium of C. subabruptus – Photo IFV.

Figure 2. Influence of relative humidity on the production of 1-octen-3-one in bunches infected with C. subabruptus.

Formation of the defect in wine
The appearance of the defect in wine cannot be explained by a simple passage from grape to must and from must to wine, as is the case with geosmin and the resulting moldy-earthy flavors. The defect is perceptible in grapes but not in the must after pressing, even when 1-octen-3-one concentrations are very high. It is probably adsorbed by other compounds, making it undetectable by smell. During the alcoholic fermentation, some of the 1-octen-3-one is broken down by the yeasts
Preventive measures
When the harvest is affected by botrytis bunch rot, rigorous clarification of the must, to a turbidity of around 50 NTU, can limit the consequences for wine quality. Use of fining agents can reduce the olfactory defect but is accompanied by a loss of structure on the palate
Spraying in the vineyard is of no use, as the fungus is an endophyte. Preventive measures, such as reducing canopy density or bunch compactness, reduce the risk of fresh mushroom off-flavor as well as attack by Botrytis
Notes
- Meistermann, E. (2006, décembre 2006). Humidité + chaleur = pourriture. Les Vins d'Alsace, 20-21.
- Panigai, L., Panon, M.-L., Bunner, D., Valade, M., & Moncomble, D. (2009). Arômes de champignon frais. Le Vigneron Champenois, 130(4), 44-65.
- Panigai, L., Panon, M.-L., Bunner, D., Valade, M., & Moncomble, D. (2009). Arômes de champignon frais. Le Vigneron Champenois, 130(4), 44-65.
- Pons, M., Dauphin, B., La Guerche, S., Pons, A., Lavigne-Cruege, V., Shinkaruk, S., . . . Darriet, P. (2011). Identification of Impact Odorants Contributing to Fresh Mushroom Off-Flavor in Wines : Incidence of Their Reactivity with Nitrogen Compounds on the Decrease of the Olfactory Defect. Journal of Agricultural and Food Chemistry., 59(7), 3264-3272. doi:https://doi.org/10.1021/jf104215a
- Meistermann, E., Villaumé, S., Goffette, D., Trarieux, C., Coarer, M., Roulland, C., & Dupont, J. (2021). A Basidiomycete Fungus Responsible for Fresh Mushroom Off-Flavour in Wines: Crustomyces subabruptus , (Bourdot & Galzin) Jülich 1978. OENO One, 55(3), 283-298. doi:https://doi.org/10.20870/oeno-one.2021.55.3.3004
- Darriet, P., Pons, M., Henry, R., Dumont, O., Findeling, V., Cartolaro, P., . . . Dubourdieu, D. (2002). 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 cerevisae. Journal of Agricultural and Food Chemistry., 50, 3277-3282. doi:https://doi.org/10.1021/jf011527d
- Meistermann, E., & Pinsun, M. (2017). Treatment with different fining agents of white musts from spoiled wine grapes. Wine Studies, 6(1). doi: https://doi.org/10.4081/ws.2017.6871
- Lafond, D., Lempereur, V., Vincent, B., & Guérin, L. (2010). Goûts moisi-terreux : Origine et moyens de lutte (Itinéraires N°23). Retrieved from https://www.vignevin.com/wp-content/uploads/2019/03/Itin23_GMT.pdf
- Le Roux, C., & Lempereur, V. (2016). Qualité du vin : agir au vignoble contre les goûts "moisi-terreux". Phytoma(692), 58-63.
References
- Meistermann, E. (2006, décembre 2006). Humidité + chaleur = pourriture. Les Vins d’Alsace, 20-21.
- Panigai, L., Panon, M.-L., Bunner, D., Valade, M., & Moncomble, D. (2009). Arômes de champignon frais. Le Vigneron Champenois, 130(4), 44-65.
- Pons, M., Dauphin, B., La Guerche, S., Pons, A., Lavigne-Cruege, V., Shinkaruk, S., . . . Darriet, P. (2011). Identification of Impact Odorants Contributing to Fresh Mushroom Off-Flavor in Wines : Incidence of Their Reactivity with Nitrogen Compounds on the Decrease of the Olfactory Defect. Journal of Agricultural and Food Chemistry., 59(7), 3264-3272. doi:https://doi.org/10.1021/jf104215a
- Meistermann, E., Villaumé, S., Goffette, D., Trarieux, C., Coarer, M., Roulland, C., & Dupont, J. (2021). A Basidiomycete Fungus Responsible for Fresh Mushroom Off-Flavour in Wines: Crustomyces subabruptus, (Bourdot & Galzin) Jülich 1978. OENO One, 55(3), 283-298. doi:https://doi.org/10.20870/oeno-one.2021.55.3.3004
- Darriet, P., Pons, M., Henry, R., Dumont, O., Findeling, V., Cartolaro, P., . . . Dubourdieu, D. (2002). 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 cerevisae. Journal of Agricultural and Food Chemistry., 50, 3277-3282. doi:https://doi.org/10.1021/jf011527d
- Meistermann, E., & Pinsun, M. (2017). Treatment with different fining agents of white musts from spoiled wine grapes. Wine Studies, 6(1). doi: https://doi.org/10.4081/ws.2017.6871
- Lafond, D., Lempereur, V., Vincent, B., & Guérin, L. (2010). Goûts moisi-terreux : Origine et moyens de lutte (Itinéraires N°23). Retrieved from https://www.vignevin.com/wp-content/uploads/2019/03/Itin23_GMT.pdf
- Le Roux, C., & Lempereur, V. (2016). Qualité du vin : agir au vignoble contre les goûts «moisi-terreux». Phytoma(692), 58-63.
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