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

The study evaluated strategies for using oenological products to mitigate the precipitation of quercetin aglycone in wines susceptible to this precipitation.

Study framework

The experimental activity was divided into several phases: Italian wines were screened for aglycone quercetin, and then a number of heterogeneous oenological products with a subtractive and stabilising action were tested.

Sixty Nebbiolo wines from nine vintages (2015–2023) from four geographical areas (Langhe-Roero, Alto Piemonte, Valtellina) were taken into consideration. The analyses carried out investigated the basic composition, phenols, aglycone quercetin and glycoside. These investigations showed that pH is correlated with the presence of aglycone quercetin: pH and ageing time influence the stability of aglycone quercetin.

Following the characterisation of the wines, the different oenological products under consideration were applied at different dosages. Single-component products were tested: chitosan, cellulose, levo and dextrorotatory gum arabic, animal-derived gelatines (High z, Low z).

Observations

The products showed heterogeneity in their action: subtractive products such as gelatines affected polyphenols and the amount of aglycone quercetin, while stabilising products such as various gum arabics preserved them.

Overall, all treatments limited the precipitation of quercetin aglycone in different ways. This study showed that gum arabics (ARABINOL and ARABINOL Dolce) were the most effective products.

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