Microwave treatment of grapes: effect on the must and red wine polysaccharide composition

Several Uruguayan wineries have begun to produce wines with minimal intervention, to increase the sustainability of their vineyards and wines. These wines are characterized by the minimum intervention in the management of the vineyard, its harvest, vinification, conservation and aging1,2. Sulfur dioxide (SO2) is not used or is used in reduced doses, although chitosan can be substituted or supplemented1. The objective of this research is to evaluate SO2 reduction or replacement options adapted to the production of Tannat red wines with minimal intervention. Vinification of the Tannat grapes with autochthonous yeasts (LN) was carried out during the 2023 vintage.

AIM: Previous research on the fruity character of red wines highlighted the role of esters [1]. Literature provides evidence that, besides these esters, other compounds that are not necessarily volatiles may have an important impact on the overall fruity aroma of wine, contributing to a masking effect [2][3]. The goal of this work was to assess the olfactory consequences of a mixture between esters and proanthocyanidic tannins, through sensory and physico-chemical approaches.

The color as well as the “clarity” of red wines are ones of the qualities required by the consumers. Red wines must have colloidal stability from its bottling to its consumption. The supplementation of red wines with additives, and especially Acacia senegal gum, contributes to its organoleptic properties such as the colloidal stabilization of the coloring matter. In a global perspective of limitation of additives in the field of enology, one of the objectives is notably (i) to reduce the use of additives in wines, by their number and/or their quantity, and (ii) to favor the use of natural additives while preserving the organoleptic and sensory qualities of wines.

Cultivar and rootstock selection are two well-known strategies for adapting vine production in challenging environments. Despite the vast diversity of rootstocks and cultivars, their effective contribution to grapevine sustainable development and acclimation to changing growing conditions remains an open question. The use of robust and prompt monitoring tools can allow a powerful screening of the water status of the vineyard before considering a further detailed characterization. This study leveraged new tools to monitor the stomatal conductance (gs), transpiration rate (E), and quantum efficiency of photosystem II (ᶲPSII) throughout a season, from pre-veraison to after-harvest.

Melatonin is a bioactive compound present in foods and beverages such as wines. During alcoholic fermentation, yeast transforms tryptophan into certain indole compounds, including melatonin. This paper aims to develop and validate a free solvent analytical method by ultra-high performance liquid chromatography coupled with high resolution mass spectrometry (UHPLC/MS-MS) to determine melatonin and its precursors (L-tryptophan, tryptamine, serotonin, tryptophol, N-acetylserotonin, 5-hydroxytryptophan, and 3- indoleacetic) that appropriately prevent the matrix effect.