New C-glucosidic ellagitannin-derived spirit compounds: Identification, quantitation and sensory contribution

Abstract

Ellagitannins consist the main extractible phenolic compounds in oak wood. They can be extracted during eaux-de-vie aging in barrels and rapidly undergo chemical transformations, such as hydrolysis, reduction, oxidation, or even substitution reactions. Given gaps in knowledge about their composition in spirits, the goal of this work was to explore ellagitannin behavior during Cognac eaux-de-vie aging and search for new C-glucosidic ellagitannin-derived compounds. A purification protocol was established in order to isolate the new formed compounds. UPLC-UV-Q-ToF and NMR spectroscopy were used to characterize a new C-glucosidic ellagitannin, named brandy tannin B. This compound was isolated from Cognac eaux-de-vie for the first time and was quantified in old aged eaux-de-vie and commercial Cognacs.

A triangular test was carried out to explore the incidence of this newly identified compound. Other oxidation compounds derived from ellagitannins, the known whiskey tannins A and B, were also identified for the first time in Cognac eaux-de-vie. It was shown that whiskey tannins A and B presented two isomeric forms. The four whiskey tannins were quantified in this matrix and followed the same trend as the brandy tannins. Both b-1-O-ethylvescalagin and b-1-O-ethylvescalin were also identified for the first time in Cognac, and their development in this matrix was also studied in order to better understand the formation of brandy tannin B. In addition, the organoleptic impact of brandy tannin B was evaluated. This work brings new insights into ellagitannin composition and their contribution to spirit quality.