IVAS 2022 banner
IVES 9 IVES Conference Series 9 IVAS 9 IVAS 2022 9 Controlling Wine Oxidation: Effects of pH on Key Reaction Rates

Controlling Wine Oxidation: Effects of pH on Key Reaction Rates

Abstract

Acidity is often touted as a predictor of wine ageability, though surprisingly few studies have systematically investigated the chemical basis for this claim. The effects of pH on the rates of several key reactions in the wine oxidation pathway were evaluated in model wine. Wine oxidation starts with the redox cycling of iron between two oxidation states: iron(II) is oxidized by oxygen while iron(III) is reduced by phenols. While iron(III) reduction slowed as pH was increased from 3 to 4, oxygen consumption by iron(II) accelerated. However, pseudo-first order rate constants for oxygen consumption remained at least ten times lower than those of iron(III) reduction, suggesting that iron(II) oxidation is the rate-determining reaction for wine oxidation, and wine aging is thus limited by oxygen ingress. Despite this, different wines subject to the same oxidative conditions will often vary in their rate of maturation, indicating another control point “downstream” in the oxidation pathway. Hydrogen peroxide formed upon the reduction of oxygen can react in one of two ways: the iron-catalyzed Fenton oxidation of ethanol into acetaldehyde, or quenching by sulfur dioxide. Acetaldehyde production from added H2O2 was faster at pH 4 than at pH 3, while the efficacy of SO2 as an antioxidant was diminished, lending credence to the notion that high-pH wines deteriorate more quickly than more acidic wines. These observations may be explained by the pH-dependent complexation of iron by tartrate and other carboxylic acids in wine, which determines the reduction potential of iron and controls its reactivity. Findings overall suggest viticultural and winemaking practices, as they pertain to the management of wine acidity, may have significant long-term repercussions on aging.

DOI:

Publication date: June 23, 2022

Issue: IVAS 2022

Type: Article

Authors

Nguyen Thi1

1Weincampus Neustadt, Institute for Viticulture and Oenology, Dienstleistungszentrum Ländlicher Raum (DLR), Breitenweg 71, 67435 Neustadt an der Weinstraße, Germany

Contact the author

Keywords

wine ageing, oxidation, iron, acidity, Fenton

Tags

IVAS 2022 | IVES Conference Series

Citation

Related articles…

The use of local knowledge relating to vineyard performance to identify viticultural terroirs in Stellenbosch and surrounds

A terroir represents grouping of homogenous environmental units, or natural terroir units, based on the typicality of the products obtained. Identification and characterisation of terroirs depends on knowledge of environmental parameters, the functioning of the grapevine and characteristics of the final product, which must be placed in a spatial context.

The impact of delayed grapevine budbreak on lemberger wine sensory compounds under variable weather conditions

Spring freeze events threaten grape production globally. As grape buds emerge from dormancy in spring, freezing temperatures have the potential to damage green tissues, decreasing yield potential and compromising fruit quality by harvest.

Shoot heterogeneity effects in a Shiraz/R99 vineyard

Nous avons fait des recherches sur l’effet de l’hétérogénéité des bourgeons sur les paramètres de la croissance végétative et reproductive, la physiologie de la vigne et la composition du raisin dans une parcelle de Shiraz/Richter 99. Des bourgeons sous-développés (typiquement plus courts et moins mûrs à la véraison) ont été comparés avec

IMPACT OF THE WINES’ QUALITY ON THE WINE DISTILLATES’ ORGANOLEPTIC PROFILE

Brandy de Jerez (BJ) is a spirit drink made exclusively from spirits and wine distillates and is characterized by the use of casks for aging that previously contained Sherries. The quality and sensory complexity of BJ depend on the raw materials and some factors: grape variety, conditions during processing the wine and its distillation, as well as the aging in the cask. Therefore, the original compounds of the grapes from which it comes are of great interest (1 y 2) being in most cases the Airén variety. Their relationship with the quality of the musts and the wines obtained from them has been studied (3) and varies each year of harvest depending on the weather conditions (4).

PRODUCTION OF A FUNCTIONAL BEVERAGE FROM WINEMAKING BY-PRODUCTS: A NEW WAY OF VALORISATION

In the challenge of transforming waste into useful products that can be re-used in a circular economy perspective, winery by-products can be considered as a source of potentially bioactive molecules such as polyphenols. The wine industry generates each year 20 million tons of by-products. Kombucha fermentation is an ancestral process which allow to increase the biological properties of tea by the action of a microbial consortium formed by yeasts and bacteria called SCOBY. It belongs to the field of healthy food for which the interest of consumers is growing. The objective of this work was to propose a new functional beverage made from winemaking by-products fermented by a Kombucha SCOBY.