Description du projet :
In winemaking, the appearance of turbidity in white wine is a serious visual defect, which lowers significantly its commercial value. A major cause of formation of turbidity in wine is attributed to the presence of temperature sensitive proteins. The proteins undergo slow conformational changes, leading to aggregation and flocculation phenomena. The process can be accelerated by exposure of wine to high temperatures during transportation or storage. In recent years heat-unstable proteins in white wine were identified as grape class IV chitinases, ß-glucanases and a fraction of thaumatin like proteins. Although proteins play a central role in the formation of turbidity, other components present in wine such as polyphenols, sulphate anion, polysaccharides as well as ionic strength and pH value play an important role in the phenomenon.
The lack of reliable tests assessing risk of protein clouding during bottle storage is a recurring problem of winemakers. Currently used test assessing haze potential involves heating which often cause overdosing of fining agent. Despite the large progress in the white wine research and substantial development of the analytical methods applied the phenomenon of white wine haze formation remains unrevealed. The traditional treatment used to stabilize wine includes addition of bentonite, which is certainly effective but due to its non-specific binding results in a considerable decrease in aroma compounds and therefore quality of wine. Thus, a strong need to establish a more selective and economically justified method of wine stabilization, which will preserve the aroma compounds in white wine, is undeniable.
This study aims at the development of more reliable haze potential tests and more specific alternative treatments for wine. To achieve this objective the knowledge on the mechanisms involved in the development of turbidity evoked by proteins of wine needs to be extended. We will use two novel approaches based on a non-destructive technique of haze analysis: a spectroscopic analysis to evaluate the particle size in suspension and a circular dichroism method to detect structural changes in wine proteins. Additionally, we will search for an innovative white wine clarification treatment based on protein polyphenol binding phenomenon. The overall objective is to provide the required knowledge and tools to allow winemakers to manage protein stability during winemaking processes.
Equipe de recherche au sein de la HES-SO:
Mathieu Marc
, Ducruet Julien
, Bach Benoit
, Gaillard Vanessa
, Andlauer Wilfried
, Cléroux Marilyn
, Bocquel Dimitri
, Udrisard Isabelle
, Maruel Frédéric
, Silvestri Anne-Claire
, Mayor Stéphane
Partenaires académiques: 425 - Oenologie; VS - Institut Technologies du vivant; Bach Benoit, 425 - Oenologie
Durée du projet:
01.12.2014 - 31.05.2017
Montant global du projet: 198'900 CHF
Statut: Terminé
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