Untargeted GC-MS metabolomics to evaluate how red grape varieties and synthetic must impact volatile profiles of grape-associated fungi

Abstract

Mycobiota from vine-to-wine is highly diverse and can affect grape quality at harvest as well as wine sensory properties, sometimes leading to off-flavors. Fresh mushroom aroma (FMA) is an off-flavor caused by some molds on grapes or in wines that produce specific volatile compounds (VOCs), the most well-known being 1-octen-3-ol and 1-octen-3-one, although many other VOCs are likely involved [1, 2, 3]. To better understand the FMA defect, a multidisciplinary approach combining predictive and classical mycology, sensorial and biochemical analyses, was used. We determined growth patterns and VOCs profiles for 18 grape-associated fungi, individually or in co-inoculation, on must media or grapes. Fastest growth rates on must media were observed for Botrytis cinerea and Penicillium crocicola although most fungi thrived in a wide range of conditions. We also determined how pH and temperature affected the growth of these grape-associated molds and some inter- and intra-specific variations were observed. Untargeted GC-MS strategy was used to identify VOCs, with a focus on FMA defect [4]. One of the originalities was to determine to what extent fungal co-inoculations modified VOC profiles and if an increase in FMA off-odors was perceived by sensorial analyses. FMA was primarily linked to Penicillium species as Penicillium crocicola. On grapes, Botrytis cinerea co-inoculated with Penicillium bialowiezense or Penicllium citreonigrum induced detectable FMA off-odors and an increase in 3-octanol and 3-octanone. We detected multiple unknown VOCs. Finally, all datasets were combined in a global analysis to identify how the matrix impacted fungal isolate VOCs profiles. A higher number of fungal VOCs were shared between Pinot Noir and Meunier grapes datasets than with must medium. VOCs profiles for B. cinerea and P. crocicola were clearly distinguished. Overall, this study provides new knowledge about changes in fungal growth kinetics and VOC profiles in musts and on grapes, with the studied fungal species thriving in a wide range of conditions. Based on the data generated, better vineyard management practices to anticipate conditions leading to FMA emergence but also related to annual climate variations favouring fungal growth could be put in place. Indeed, our results suggest there may be a need for more intensive fungal community surveillance in the vineyards. Predictive tools could also be developed for early detection.

References

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3. Destanque, A., Picot, A., Pensec, F., Pawtowski, A., Rolland, N., Treguer-Fernandez, S., Debaets, S., Guerin, L., Mercier, L., Coton, E., Herve, M., Coton, M. (2024). Grape berry mycobiota and its contribution to fresh mushroom aroma off-odour in wine. OENO One, 58(4). https://doi.org/10.20870/oeno-one.2024.58.3.8105

4. Destanque, A.; Pensec, F.; Picot, A.; Thierry, A.; Maillard, M.-B.; Commereuc, A.; Poirier, E.; Coroller, L.; Coton, E.; Hervé, M.; Coton, M. (2025). Contribution of grape-associated fungal species to the FMA defect on grapes and in musts. LWT, 118945.