PRECISE AND SUSTAINABLE OENOLOGY THROUGH THE OPTIMIZED USE OF AD- JUVANTS: A BENTONITE-APPLIED MODEL OF STUDY TO EXPLOIT

Abstract

As wine resilience is the result of different variables, including the wine pH and the concentration of wine components, a detailed knowledge of the relationships between the adjuvant to attain stability and the oenological medium is fundamental for process optimization and to increase wine durability till the time of consumption.

This work merges our 10-years’ studies¹ on bentonite along with information from the literature to design a study-model feasible to optimize the effects of adjuvants by maximizing the impact on targeted compounds, while minimizing the one on desirable wine components. The boosting was simply based on the frequently unintended uses of oenological adjuvants by winemakers based also on some lacking in the EU regulations, which produces jeopardized main and side-effects, as the ones by bentonite are emblematic.

Indeed, there is no EU regulated upper limit for the addition of bentonite during the winemaking process, but the International Oenological Codex establishes the properties of the oenological bentonites amending the three classes of Ca-, Na-, and Na-activated bentonite.

Our studies demonstrated that the from-bentonite enrichment in wine cations results from the clay Cation Exchange Capacity (CEC) and from the pH, ethanol content and ionic strength which also impact on the residual card-house clay structure that is an important property for deproteinization. Indeed, for the removal of hazing forming proteins (b-glucanases, thaumatin-like proteins, chitinases) clay properties as CEC, Swell Index (SI), and Specific Surface Area (SSA) as well as wine pH are more impacting than the bentonite dose.

Considering adjuvant side-effects, bentonite can remove phenolic compounds so to modify wine colour and astringency. About terpenic wines, double addition to must for clarifying and to wine for fining outlined less removal than to the solely wine treatment. Removal of aglycones by low doses and of glycosylated terpenols especially by Ca-bentonite were predicted by RSM. For the fermentative aroma compounds, adsorption intensity and capacity more depended on the characteristics of the bentonite (SSA and CEC) than on the properties of the substances: the main removal is an indirect effect of deproteinization, while a direct adsorption can be described by the Freundlich equation for only a few compounds.

1. Lambri M., Colangelo D., Dordoni R., Torchio F., De Faveri D.M. (2016). Innovations in the Use of Bentonite in Oenology: Interactions with Grape and Wine Proteins, Colloids, Polyphenols and Aroma Compounds, Chapter 18 in (Ed. Morata A. and Loira I., Intech Publisher) book: Grape and Wine Biotechnology. p. 381-400. ISBN 978-953-51-2692-8.