Study in collaboration with the University of Turin
DISAFA Oenology, Alba campus

Techniques for mitigating quercetin precipitation in wines

PRECIPITATION OF QUERCETIN IN WINES

MITIGATION TECHNIQUES

State of the art

Quercetin is present in wines in both glycoside and aglycone forms. The aglycone form is unstable and has low water solubility (0.4 µg/mL). In wines, its concentration can vary from 0 to 40 mg/L. The presence of high concentrations of quercetin aglycone, combined with low anthocyanin levels, can increase the tendency toward precipitation. In addition, climate change and the reduction of anthocyanin content make wines more susceptible to instability.

This study evaluated strategies based on the use of oenological products to mitigate the precipitation of quercetin aglycone in wines prone to this phenomenon.

Study framework

The experimental activity was divided into several phases. Italian wines were first screened for aglycone quercetin, after which a range of heterogeneous oenological products with subtractive or stabilizing action was tested.

Sixty Nebbiolo wines from nine vintages (2015–2023), originating from four geographical areas (Langhe-Roero, Alto Piemonte, and Valtellina), were considered. The analyses investigated basic composition, phenolic content, aglycone quercetin, and quercetin glycosides. The results showed that pH is correlated with the presence of aglycone quercetin: both pH and ageing time influence aglycone quercetin stability.

Following wine characterization, the selected oenological products were applied at different dosages. Single-component products were tested, including chitosan, cellulose, levo- and dextrorotatory gum Arabic, and animal-derived gelatins (high-z and low-z).

Observations

The products showed heterogeneous behavior. Subtractive products such as gelatins affected polyphenol content and reduced aglycone quercetin levels, while stabilizing products such as the various gum Arabic preserved them.

Overall, all treatments limited quercetin aglycone precipitation through different mechanisms. The study demonstrated that gum Arabic (ARABINOL and ARABINOL Dolce) were the most effective products.

Study in collaboration with the University of TurinDISAFA Oenology, Alba campus