Quantification of quercetin and quercetin-3-glucoside in Nebbiolo red wines

Abstract

Quercetin-3-glucoside, a grape flavonol defence metabolite, is extracted during winemaking and may undergo subsequent degradation in wines. Hydrolysation reactions lead to the formation of the aglycone quercetin, which presents limited solubility in the wine matrix and can induce visible precipitations. This issue potentially affects a wide range of wines. Red wines with low anthocyanin content, such as those produced from cv. Sangiovese grapes, seem more prone to quercetin instability [1]. Few cases of quercetin precipitation have been recently observed in wines from cv. Nebbiolo, a grape variety often destined to the production of monovarietal wines presenting a high content of phenolic compounds but low and oxidation-prone red colour pigments [2].

In this preliminary assessment, the quercetin-3-glucoside and (aglycone) quercetin contents were evaluated in 60 cv. Nebbiolo wines (containing a minimum varietal content of 90% or as monovarietal) covering a range of variability in terms of growing zones (Langhe, Roero, and Valtellina terroirs in northern Italy), production stages (bottle, tank, cask), and vintages (2012 to 2023), with most wines belonging to the last four vintages. Wine acidity and pH, as well as colour and key phenolic traits were also determined to investigate possible relations [1-3].

The average quercetin-3-glucoside and quercetin contents found were 1.8 and 8.0 mg/L, respectively, with high coefficients of variation (above 65%). Moreover, 18 wines presented quercetin amounts above 12 mg/L, with the highest detected concentration being 18.0 mg/L. For quercetin-3-glucoside, the maximum value was 10.8 mg/L, while no residual content was found in 37 wines, although these latter preserved a variable aglycone presence (5.6 ±5.0 mg/L). The average aglycone contents found are higher with respect to those from a previous survey of 22 cv. Sangiovese wines (estimated average below 5 mg/L, range 0.4-8.6 mg/L) [1]. No relevant correlations for quercetin were found with total anthocyanin content or colour intensity, however a strong negative correlation between wine pH and quercetin concentration was evidenced (p<0.001). The role of pH is highlighted as a possible influencing factor concerning wine quercetin content and its stabilization.

Acknowledgments

We would like to thank the Consorzio di Tutela dei Vini di Valtellina (Sondrio, Italy), Giulia Viglietti and Sergio Molino (studioMolino, La Morra, Italy) and their associates for providing the wines used in this assessment.

References

[1] Gambuti, A., Picariello, L., Rinaldi, A., Forino, M., Blaiotta, G., Moine, V., Moio, L. (2020). J. Sci. Food Technol., 57, 2602-2611.

[2] Giacosa, S., Parpinello, G. P., Río Segade, S., Ricci, A., Paissoni, M. A., Curioni, A., Marangon, M., Mattivi, F., Arapitsas, P., Moio, L., Piombino, P., Ugliano, M., Slaghenaufi, D., Gerbi, V., Rolle L. & Versari, A. (2021). Food Res. Int., 143, 110277.

[3] OIV (2023). Compendium of International Methods of Wine and Must Analysis. OIV, Dijon, France.