Brown Marmorated Stink Bug taint in grape must and wine: time evolution of trans-2-decenal

Melatonin is a bioactive compound with antioxidant properties, that has been found in many fermented beverages, such as beer and wine [1]. Indeed, it has been shown that yeast can synthesize melatonin during alcoholic fermentation, although its role inside the cell, as well as the metabolic pathway involved in its synthesis, is still unclear [1]. Recent studies showed that during fermentation, melatonin interacts with different proteins of the glycolytic pathway in both Saccharomyces and non-Saccharomyces yeast, for instance glyceraldehyde 3-phosphate dehydrogenase, pyruvate kinase or enolase [2].

From the chemical angle, Champagne wines are complex hydro-alcoholic mixtures supersaturated with dissolved carbon dioxide (CO₂). During the pouring process and throughout the several minutes of tasting, the headspace of a champagne glass is progressively invaded by many chemical species, including gas-phase CO₂ in large majority. CO₂ bubbles nucleated in the glass and collapsing at the champagne surface act indeed as a continuous paternoster lift for aromas throughout champagne or sparkling wine tasting [1]. Nevertheless, inhaling a gas space with a concentration of gaseous CO₂ close to 30% and higher triggers a very unpleasant tingling sensation, the so-called “carbonic bite”, which might completely perturb the perception of the wine’s bouquet.

Alcoholic fermentation is the main step for winemaking, mainly performed by the yeast Saccharomyces cerevisiae. But other wine yeasts called non-Saccharomyces may contribute to alcoholic fermentation and modulate the wine aroma complexity. The recurrent problem with the use of these non-Saccharomyces yeasts is their trend to die off prematurely during alcoholic fermentation, leading to a lack of their interesting aromatic properties searched in the desired wine. This phenomenon appears to be mainly due to interactions with S. cerevisiae. These interactions are often negatives but remain unclear because of the species and strain specific response. Among the non-Saccharomyces yeasts, Lachancea thermotolerans is a wine yeast naturally found in grape must and well known as a great L-lactic acid producer and an aromatic molecules enhancer, but its behavior during alcoholic fermentation can be completely different in co-fermentation with S. cerevisiae in function of strain used.

Light-struck taste is a defect prevalent in white wines bottled in clear glass light-exposed for a considerable amount of time leading to a loss of color and appearance of sulfur-like odors. The reaction involves riboflavin (RF), a highly photosensitive compound that undergoes to intermolecular photoreduction by the uptake of two electron equivalents from an external donor, the methionine. The reaction includes different steps forming methional which is extremely unstable and decomposes to methane thiol and acrolein. The reaction of two molecules of methane thiol yields dimethyl disulfide. Methane thiol is highly volatile, has a low perception threshold (2 to 10 µg/L in wine) and confers aroma-like rotten eggs or cabbage.

In April 2024, the French official catalog includes 449 grape varieties and rootstocks. In 10 years it has been enriched with 70 varieties. It is an indisputable marker of the interest of professionals in genetic resources of all origins and the expectations they have to prepare the viticulture of the future. The scientific community has now put all irons in the fire and is not neglecting any avenue of adaptation. The regular decline in the use of phytosanitary products and the already marked effects of climate change are the targets of varietal improvement.