The use of viticultural and oenological performance of grapevines to identify terroirs: the example of Sauvignon blanc in Stellenbosch

Bentonite fining is commonly used in oenology to remove all or parts of white wine proteins, which are known to be involved in haze formation. This fining is effective, but has disadvantages: it is not selective, thus molecules responsible for aroma are also removed, it causes substantial volume losses, and finally it generates wastes. Over the last decades, the knowledge of wine proteins has increased: they have been identified, their structures are known, some of them have been crystallized.

Contribution Sparkling wines elaborated following the traditional method undergo a second fermentation in closed bottles of base wines, followed by aging of wines with lees for at least 9 months. Most of the sparkling wines elaborated are white and rosé ones, although the production of red ones is highly increasing. One of the initial problems in red sparkling wine processing is to obtain suitable base wines that should have moderate alcohol content and astringency and adequate color intensity; which is difficult to obtain when grapes must be harvested at low phenolic and industrial maturity stage. The low phenolic maturity degree in the red grapes makes essential to choose an adequate winemaking methodology to obtain the base wines because the extracted polyphenols will vary according the winemaking technique: carbonic maceration or destemmed-crushed grapes.

Fumaric acid has been approved by the OIV in 2021 for its application on wine to control the growth and activity of lactic acid bacteria. Fumaric acid is currently being evaluated by the OIV as an acidifier of must and wine. Investigations during the 2023 vintage provided further information on its use on must or during AF, thus completing information provided during the previous vintage.

Les effets de l’état hydrique et de l’alimentation en azote sur le potentiel aromatique des raisins de Sauvignon blanc ont été mesurés sur des vignobles du Bordelais. Les déficits hydriques ont été caractérisés par le potentiel tige déterminé en milieu de journée ΨTmin)­. L’alimentation en azote a été étudiée à partir d’une zone carencée en azote. Une part de cette zone a été supplémentée avec de l’azote minéral.

La véraison, stade intermédiaire du développement de la baie de raisin, correspond au début de la maturation. Aux modifications de coloration de la pellicule sont associées une perte de fermeté, une diminution de l’acidité et une augmentation des teneurs en sucres et pigments ainsi que du volume de la baie. Le stade de véraison des cépages blancs reste difficile à apprécier visuellement. Son évaluation par palpation est subjective et donc sujette à caution.