MICROVARIOR - Organic wines made from resistant grape varieties: analysis of the microbiota of grape berries and their potential for spontaneous fermentation in pesticide-free organic agriculture

OBJECTIVES

The use of resistant varieties is a topical alternative in the context of organic practices based on limiting inputs, both in the vineyard and in the winery. 

Spontaneous fermentation is frequently used in organic winemaking, but its success is partially dependent on the presence of fermenting yeasts on the mature grape berries. 

Since no data is available about the microbiota associated with resistant varieties (Artaban, Floréal, G5 and G14), its composition as a function of variety (resistant vs. conventional) and organic, low-input or pesticide-free management methods was studied in this project.

REALISATIONS

Three experimental domains or INRAE research stations and one private one were selected in three different wine-growing regions to assess the impact of biotic and abiotic factors on microbiota diversity.

Analysis of grape berry microbiota revealed a strong regional and vintage effect across all varieties. A resistant vs. conventional variety effect was also observed.

On the other hand, the management methods used did not lead to any major differences in the microbiota of the berries, while fermentation kinetics differed at the level of the micro-fermentations. Furthermore, the use of small fermentation volumes (1 L) proved unsuitable for spontaneous fermentations under controlled conditions.

Finally, analysis of the aromatic compounds produced during fermentation and sensory analysis of the wines obtained from fermentation at the pilot scale showed that there was no impact of the management method (organic or pesticide-free) on the final quality of the wines.

This exploratory project paves the way for a larger-scale analysis of the microbiota of resistant varieties. Other viticultural systems will have to be explored, and other parameters such as berry maturity or the agroecological environment of the vineyard plots will have to be taken into account in order to rank the factors that structure variations in berry microbiota. In addition, in order to explain the variety effect observed, one possibility would be to study variations in berry skin composition.

Participants

INRAE units

• MAIAGE, Jouy-enJosas
• Œnologie, Bordeaux
• Pech Rouge, Gruissan
• SAVE, Bordeaux
• SPO, Montpellier
• UEAV, Colmar
• Vigne, Bordeaux

Partners

• Château Coupe-Roses wine estate IFV