The influence of external factors on the alcoholic fermentation of wine yeasts

Reduction of sulfur dioxide during winemaking is a request from the wine industry. To replace sulfur dioxide, various alternatives exist, including bioprotection by yeast inoculation. This practice consists in adding non-Saccharomyces yeasts directly on the grapes or must.

Volatile sulfur compounds (VSCs), mainly hydrogen sulfide and methanethiol (H2S and MeSH), are the responsible for reductive off-odor in wine.

L’entreprise viticole Concha y Toro S.A. gère environ 600 ha de vignes dans la Vallée du Maipo (A.O. Valle del Maipo). L’objectif est celui de caractériser spatialement ces vignobles et leur occupation du sol environnante. Le choix s’est porté vers la démarche de zonage viticole par l’analyse spatiale, utilisant des traitements d’images satellitaires afin d’avoir une vision synoptique de la zone à moindres coûts et délais. Un système d’informations géographiques (SIG) est construit à partir des données suivantes : cartes topographiques, géologique, fond cadastral numérique, images satellitaires. Un modèle numérique de terrain est par ailleurs construit à une résolution de 25 m à partir des cartes topographiques.

Wine oxidation phenomena during the different processes of winemaking, aging and storage are closely related to the presence of oxygen and to the wine’s capacity for consumption.

Protein haze in white wines is a major technological and economic problem of the wine industry. Field tests were carried out in steep slope vineyards planted with Riesling grapes over 3 dry growing seasons to study the effect of drought stress on the concentration of proteins in the resulting wines. Plots suffering from drought stress were compared with surrounding drip irrigated plots. Riesling grapes were processed into wines by conventional procedures. Protein amounts of the isolated wine colloids of the stressed samples were always higher than those of the watered samples(mean watered 13.8 ± 0.44, mean stressed 17.4 ± 0.40 g 100 g-1). As a consequence, higher bentonite doses were needed to achieve protein haze stability of the drought stressed treatments.