Influence of oenological tannins on malvidin-3-O-monoglucoside copigmentation in a model wine solution

Jordi Gombau,Pierre-Louis Teissedre,Joan Miquel Canals,Adeline Vignault,Isidro Hermosín,Sergio Gómez-Alonso,Fernando Zamora,Olga Pascual,Esteban Gracía-Romero

doi:10.20870/oeno-one.2019.53.3.2412

Abstract

Aim: The aim of the study was to evaluate the effects of five different oenological tannins on the color of a malvidin-3-O-monoglucoside solution, and thereby assess the effectiveness of these tannins as copigments.Methods and results: Solutions containing malvidin-3-O-glucoside and different doses of copigments were prepared. The malvidin-3-O-glucoside concentration of the solutions, and color parameters, were measured after 1 and 7 days.Conclusions: On days 1 and 7, a decrease in lightness and hue, and an increase in chroma, absorption at 520 nm and wavelength of maximal absorption were observed in solutions containing the oenological tannins. A decrease in malvidin-3-O-glucoside concentration in the tannin-containing solutions compared with the control solution was detected on day 7. The extent of this decrease depended on the specific tannin. Some changes in color parameters on day 7 compared with day 1 were observed, which were probably due to the formation of new pigments. The total color difference between the different malvidin-3-O-glucoside solutions and a pure white solution was calculated to estimate the effectiveness of the different tannins as copigments.Significance and impact of the study: These results prove that supplementation with oenological tannins is a viable option for improving the color of red wines. A copigmentation index is proposed for measurement of the effectiveness of copigments.

Highlights

The use of oenological tannins is common practice in winemaking
It can be concluded that all the oenological tannins investigated are good copigments, because they improve the color of a malvidin-3O-glucoside solution
Vignault et al (2019) obtained similar results and have shown that pH and ethanol content have an important influence on the copigmentation effectiveness of oenological tannins

Summary

Introduction

The use of oenological tannins is common practice in winemaking. The use of tannins is authorized by the International Organisation of Vine and Wine (OIV) only for facilitating the clarification of wines and musts (OIV, 2017), it is unquestionable that they are used for many other purposes. Several other properties have been attributed to oenological tannins, such as antioxidant activity (for protection of wines against oxidation) (Hagerman et al, 1998), direct consumption of dissolved oxygen (Pascual et al, 2017), the ability to scavenge peroxyl radicals (Magalhaes et al, 2014), the ability to chelate iron(II), prevention of oxidative damage mediated by Fenton-based reactions (Pérez et al, 2009), antioxidasic activity (antilaccase activity) (Obradovic et al, 2005), improvement of wine structure and mouthfeel (Vivas, 2001), color improvement and stabilization of red wines (Canuti et al, 2012), copigmentation effect (Neves et al, 2010), direct formation of new pigments (Versari et al, 1998), elimination of reduction odors (Vivas, 2001) and even bacteriostatic effects (Lempereur et al, 2002a). The structure of various ellagitannins have been described, but castalagin and vescalagin are the most abundant in oak wood, accounting for between 40% and 60% of the total by weight (Fernández de Simón et al, 1999)

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Conclusion