277: Tannins, Anthocyanins, and Other Polyphenols in Virginia Cabernet Franc Finished Wines

Introduction

Cabernet Franc (CF) is the most widely grown grape in Virginia and, outside of the Loire Valley in France, Virginia grows more CF grapes than any other region in the world. CF grapes are versatile and used to make red wines with different styles and flavors. These variations are due, in large part, to the composition of tannins, anthocyanins, and other polyphenols in the wine. However, despite the prominence of Virginia CF wine in the global wine market, there are virtually no data on its polyphenol content. Therefore, the goal of this project was to comprehensively quantify polyphenols in Virginia CF wines from multiple vintages and establish a database of polyphenols in Virginia’s flagship wine.

Methods

50 CF finished wines were collected from 35 wineries across Virginia, representing 2019-2023 vintages. All wines were analyzed for the following: total polyphenols (via the Folin-Ciocalteu assay), total tannins (via the methyl cellulose precipitation assay), monomeric and polymeric anthocyanins (via the pH differential method (total monomeric anthocyanins (TMA) assay) and the bisulfite bleaching method, respectively). Individual polyphenols were measured via LC-MS/MS, including 13 anthocyanins, 12 phenolic acids, 4 catechins, 2 stilbenes, and 4 other flavonoids.

Results

Total phenolic content ranged from 1145-3113 mg gallic acid Eq./L (average: 2089 mg/L), tannins ranged from 52-171 5mg epicatechin Eq./L (average: 652 mg/L), total monomeric anthocyanins ranged from 0.93-26.06 mg cyanidin-3-O-glucoside Eq./L (average: 8.67 mg/L), and the percentage of polymeric anthocyanins ranged from 53.35%-69.87% (average: 64.71%). Regarding individual polyphenols, Malvidin 3,5-diglucoside was the most prominent anthocyanin, while phenolic acids and catechins were also present in high amounts.

Significance

The data collected in this study shows that Virginia CF wines have wide variations in polyphenol content, especially tannins and anthocyanins. These differences, which most likely stem from different viticultural and vinicultural practices, highlight the diverse phenolic composition of these wines, which impact the flavor and style of CF finished wines. These foundational data can be used to better understand phenolic composition of finished CF wines and adjust winemaking processes to create CF wines with desirable characteristics.

Authors: Muheng Li, Joy Ting, Alicia A Sarratt, Dennis P Cladis