Effect of alcoholic strength on the phenolic and furfural compounds of Brandy de Jerez aged in Sherry Casks®

Abstract

Brandy is a spirit drink produced from wine spirit aged for at least six months in oak casks with a capacity of less than 1000 L and minimum alcohol by volume (ABV) of 36%. During the aging process, physicochemical and sensory changes take place. Manifested by colour, flavour or aroma variations that improve the quality of the initial distillate. Influenced by several factors related with aging process itself and the characteristics of casks: botanical origin, volume, toasting degree, previous usage and pre-treatments, like the wine-seasoning process.Casks that have previously contained a Sherry wine (Fino, Oloroso, etc) gives rise to the so-called Sherry Cask®. The characteristics of Sherry Casks depends on the Sherry wine previously contained. They contribute during brandy aging with compounds from the wood, as well as with those from the wine that were retained in the wood’s pores. Potential extraction of these compounds is influenced by alcoholic strength. Traditionally, distillates are aged at between 50-70% ABV, although in some wineries at the alcoholic strength for consumption. Moreover, alcoholic strength has a direct impact on the logistics of the winery. An aging process with distillates of a higher alcoholic strength allows to obtain a greater volume of the final product (36% ABV) with less barrels required for the process. Barrels represent an immobilised asset for the wineries that has a direct impact on the production costs. Due to its importance, this work aims to study the influence of alcoholic strength on the composition of phenolic compounds in brandies aged for 12 months in Sherry Cask.Methods: A distillate at 77% ABV was hydrated with demineralised water to reach the different alcoholic strengths to be tested: 40%, 55% and 68% ABV. Brandies were aged in American oak (Quercus alba) casks, medium toast, with a capacity of 500 L and seasoned by 18% ABV Oloroso Sherry wine for 3 years. Distillates and Sherry Casks were supplied by Bodegas Fundador SLU, belonging to GI of Brandy de Jerez. Each test was carried out in duplicate, two barrels for each alcoholic strength, following a static aging process and samples were taken periodically to follow their evolution, showing in this study results up 12 months. The phenolic and furfural compounds were quantified by UHPLC. The results are expressed in mg/L 100% vol. alcohol in order to the different alcoholic strengths could be compared. Results: Brandies aged with lower alcoholic strength lead to a greater accumulation of phenolic compounds. In general, between 40 and 55% ABV there are no differences, while at 68% ABV lower values are obtained. This difference is more marked in phenolic acids (Gallic, Ellagic, Syringic and Vanillic acids) and furanic aldehydes (Furfural, 5-methylfurfural, 5-HMF) than in phenolic aldehydes (Vanillin, Syringaldehyde, Coniferaldehyde, Sinapaldehyde). For phenolics from wine-seasoning higher values was found for 40% ABV (Caffeic and Coumaric acids).