Role of Grape-Extractable Polyphenols in the Generation of Strecker Aldehydes and in the Instability of Polyfunctional Mercaptans during Model Wine Oxidation.

Elena Bueno-Aventín,Purificación Fernández-Zurbano,Ana Escudero,Vicente Ferreira

doi:10.1021/acs.jafc.1c05880

Abstract

Polyphenolic fractions from Garnacha, Tempranillo, and Moristel grapes were reconstituted to form model wines of identical pH, ethanol, amino acid, metal, and varietal polyfunctional mercaptan (PFM) contents. Models were subjected to a forced oxidation procedure at 35 °C and to an equivalent treatment under strict anoxia. Polyphenolic profiles significantly determined oxygen consumption rates (5.6–13.6 mg L–1 day–1), Strecker aldehyde (SA) accumulation (ratios max/min around 2.5), and levels of PFMs remaining (ratio max/min between 1.93 and 4.53). By contrast, acetaldehyde accumulated in small amounts and homogeneously (11–15 mg L–1). Tempranillo samples, with highest delphinidin and prodelphinidins and smallest catechin, consume O2 faster but accumulate less SA and retain smallest amounts of PFMs under anoxic conditions. Overall, SA accumulation may be related to polyphenols, producing stable quinones. The ability to protect PFMs as disulfides may be negatively related to the increase in tannin activity, while pigmented tannins could be related to 4-methyl-4-mercaptopentanone decrease.

Highlights

Wine longevity is a complex multifactor phenomenon in which the weight of the different factors is not well known
This property can be defined as the ability of the wine, under an exposure to oxygen, to keep its color, avoid accumulation of acetaldehyde and Strecker aldehydes (SAs), and keep as long as possible labile varietal aroma compounds, such as polyfunctional mercaptans (PFMs)
The main goal of the present research is to assess, the role played by the polyphenolic composition on the ability of wine models to accumulate SAs and to retain PFMs and other varietal aroma compounds during oxidation

Summary

Introduction

Wine longevity is a complex multifactor phenomenon in which the weight of the different factors is not well known. The hydrogen peroxide formed in the first two-electron reduction of O2, taken from an odiphenol, reacts with Fe(II) cations to form the powerful hydroxyl radical, OH. Once formed, this radical is a very powerful oxidant, which reacts at diffusion-controlled rates. It is, proposed that it reacts close to its site of production with the first potential substrate it encounters.[1] This implies that most of it oxidizes ethanol to form 1hydroxyethyl radical (1-HER), and this, in the presence of oxygen, forms 1-hydroxyethyl peroxyl which decomposes into acetaldehyde.[2,3] the reaction is quite complex. The accumulation of acetaldehyde in response to O2 consumption is very difficult to predict

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