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 & 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.

Bentonite fining is the most popular treatment used to remove proteins in white and rosé wines. The usual heat test used to adjust the bentonite dose consists of heating the wine during 30 min at 80 °C. At this temperature, all of the proteins are unfolded, and this can lead to an overestimation of the dose. We have shown that proteins adsorb on bentonite in a specific order and, more importantly, that the proteins responsible for haze formation adsorb first. Fluorescence spectroscopy showed that this is due to the structural properties of proteins, which can be classified as hard and soft proteins. Alternative heat tests were performed at a lower temperature (40 °C) and showed a better correlation with accelerated aging. These tests were also less dependent upon the wine pH.

Fining agents have evolved significantly over the last twenty years. The need for winemakers to have objective references about the new products has prompted this study. The experiment consists in comparing the new fining products (charcoal, pea proteins, derivatives of chitin and composite products generally mixing PVPP + various proteins + bentonite) with reference products such as casein and PVPP and with non-treated controls. Fining agents were applied during clarification of 15 different musts obtained from wine grapes affected by different degrees and types of rot: fresh and dry Botrytis cinerea rot, powdery mildew and Botrytis contaminated with other fungi (Aspergillus, Penicillium, Basidiomycetes), giving the bunches offflavours that were earthy and resembled fresh mushrooms. This study highlights the importance of good clarification of musts. The quality of control wines, without any treatment, increases with the clarity of the must. In most experiments, clarification of the must around 50 Nephelometric Turbidity Units (NTU) can eliminate or reduce any organoleptic defects in wine without fining. Use of pectolytic enzymes may be necessary in order to reach this level of clarity. The new allergen-free fining agents have the same effectiveness as reference products such as casein and polyvinylpolypyrolidone (PVPP). Composite products are more efficient than pea protein alone and less than products including charcoal. However, the improvement of aromatic quality goes hand in hand with loss of body and persistence.

The regulation of oenological practices put in place in Europe at the beginning of the 20th century was intended to save traditional viticulture from the excesses of liberalism and the manufacture of artificial wines. The foundations of this regulation have been taken up by European texts and are still in force today. Over the last fifteen years, in order to improve the competitiveness of the sector in a context of global competition, practices have become more and more numerous and they are sometimes moving away from these foundations. The new environmental, societal and commercial challenges facing the wine sector may well call into question the current production model and give rise to reflections on the definition of wine.

Fining agents have evolved significantly over the last twenty years. The need for winemakers to have objective references about the new products has prompted this study. The experiment consists in comparing the new fining products (charcoal, pea proteins, derivatives of chitin and composite products generally mixing PVPP + various proteins + bentonite) with reference products such as casein and PVPP and with non-treated controls. Fining agents were applied during clarification of 15 different musts obtained from wine grapes affected by different degrees and types of rot: fresh and dry Botrytis cinerea rot, powdery mildew and Botrytis contaminated with other fungi (Aspergillus, Penicillium, Basidiomycetes), giving the bunches offflavours that were earthy and resembled fresh mushrooms. This study highlights the importance of good clarification of musts. The quality of control wines, without any treatment, increases with the clarity of the must. In most experiments, clarification of the must around 50 Nephelometric Turbidity Units (NTU) can eliminate or reduce any organoleptic defects in wine without fining. Use of pectolytic enzymes may be necessary in order to reach this level of clarity. The new allergen-free fining agents have the same effectiveness as reference products such as casein and polyvinylpolypyrolidone (PVPP). Composite products are more efficient than pea protein alone and less than products including charcoal. However, the improvement of aromatic quality goes hand in hand with loss of body and persistence.