Tannin Content in Vitis Species Red Wines Quantified Using Three Analytical Methods.

Aude A Watrelot

doi:10.3390/molecules26164923

Abstract

Tannin content in red wines is positively correlated with astringency perception and wine grade; however, tannin quantification is one of the main challenges. In this study, tannin content was quantified using three analytical methods in commercial red wines from Vitis vinifera and interspecific cold-hardy hybrids including Marquette, Frontenac, and Petite pearl cultivars. Protein (PP) and methylcellulose precipitation (MCP) methods were compared to a HPLC-DAD method, which is based on the interaction between tannins and a hydrophobic surface (RPC). Frontenac wines were the poorest in tannins and Cabernet sauvignon wines were the richest regardless of the method used. In cold-hardy red wines, the tannin content was higher in Marquette with high alcohol content, which suggested that the tannins were extracted from seeds rather than skins. The high limit of quantification of the PP method and the presence of anthocyanin di-glucosides in cold-hardy wines were parameters suggesting that protein and methylcellulose precipitation methods were neither suitable nor reliable for the quantification of tannins in cold-hardy red wines. The tannin content quantified by RPC was positively correlated to tannin quantified by MCP, suggesting that the RPC method would be relevant for the quantification of tannins in red wines.

Highlights

In red wine, tannins are considered to be of fundamental importance to quality, as they impart astringency [1]
The tannin content determined by protein precipitation and methylcellulose precipitation methods is not consistent across the research [14], and it seems to be highly dependent on the method applied, the structure of the tannins, and the presence of other matrix compounds [15]
In Frontenac wines, the average tannin content was below the limit of quantification of the protein precipitation method as previously observed, and it decreased after the end of alcoholic fermentation, which was possibly due to interactions between proteins and tannins [19]

Summary

Introduction

Tannins are considered to be of fundamental importance to quality, as they impart astringency [1]. An alternative method by high-performance liquid chromatography using a hydrophobic surface under a gradient of solvents (RPC) has been previously developed to characterize the tannin content and activity, but no correlation between the precipitation methods and this reversed-phase chromatography method in different red wines has been reported before [4,7,22,23]. The latter method is based on the ability of tannins to bind to a hydrophobic surface, but it does not discriminate depending on tannin structure or tannins already associated to macromolecules

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Conclusion