The effect of bentonite fining on the volatile and non-volatile profile of Italian white wines

Protein instability is the main non-microbial issue in white wines that results in the formation, during storage, of haze that results in lower value of the wines produced. Winemakers have been preventing this issue by adding bentonite, a clay that binds to the positively charged wine proteins that are subsequently removed together with Bentonite. Bentonite fining is the most used technique for removing proteins from white wine worldwide. However, bentonite is not specific for wine proteins, and therefore with its use winemakers could remove also useful compounds in wine, such as phenolics, volatiles, and nonvolatile compounds, which are known to contribute to the wine's sensory attributes. In this study, initially the minimum required amount of bentonite to reach wine protein stability was defined, and samples from 7 Italian white wines varieties were stabilized with bentonite addition. After this treatment, that the impact of bentonite fining on wine chemical composition, as well as the total phenolics, volatiles, and nonvolatile profiles were studied by means of colorimetric and chromatographic techniques. Results showed that wines contained different amounts of haze-forming proteins (chitinases and thaumatin-like proteins), with an associated significant decrease in total phenolic concentration, decrease in titratable acidity and a consequent increase in pH. The other general characteristic (organic acid profiles, ethanol content, sugar content) of wines showed slight difference in bentonite treated wines compared to untreated wines. This abstract might be improved in final version according to further results.