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…

Projected impacts of climate change on viticulture over France wine-regions using downscalled CMIP6 multi-model data

Winegrape is a crop for which the quality and the identity of the final product depends strongly on the
climatic conditions of the year. By impacting production systems and the way in which wines are
developed, climate change represents a major challenge for the wine industry (Ollat et al., 2021).

Read More

Response of red grape varieties irrigated during the summer to water availability at the end of winter in four Spanish wine-growing regions: berry phenolic composition

Water availability is the most limiting factor for vineyard productivity under Mediterranean conditions. Due to the effects caused by the current climate change, wine-growing regions may face serious soil moisture conservation problems, due to the lower water retention capacity of the soil and higher soil irradiation. The aim of this work was to evaluate the effects of soil recharge irrigation in pre-sprouting and summer irrigation every week (30 % ETo) from the pea size state until the end of ripening (RP) compared to exclusively summer irrigation every week (R) in the same way that RP, on berry phenolic composition at harvest.

Read More

Impact and comprehension of nitrogen and lipid nutrition on the production of fermentative aromas with different S. Cerevisiae yeasts used for spirits

In the Cognac appellation, the production of white wines is almost exclusively dedicated to elaborate Charentaise eaux-de-vie. In this sense, the quality of Cognac eaux-de-vie intrinsically depends on the quality of the base wines subjected to the distillation stage. In this context, the production of these base wines differs from those of classic white wines to release particular organoleptic properties during the distillation stage.

Read More

Subsurface irrigation: a means to reduce chemical and water inputs in vineyards

Grape growers around the world are seeking to reduce their reliance on herbicides. However, traditional alternatives to chemical weed control do not always integrate seamlessly into established vineyard operations. Employing nonchemical weed management often requires trellis alterations, purchasing or hiring new equipment, and depending on region, may significantly increase tractor passes required to reach desired level of weed control. Critical thinking and thoughtful strategies are necessary to minimize expenditures and maintain quality during the transition away from herbicides. In this trial, irrigation was installed underground in an effort to minimize water loss due to evaporation, better direct the water to the vines, and reduce weed growth in the difficult to control undervine area.

Read More

Identifying research opportunities at Douro Demarcated Region

The Douro Demarcated Region, in Northern Portugal, offers outstanding wines with unique characteristics. Due to the today’s globalized marketplace, local producers often need to further develop their cultivation techniques to remain competitive. The Association of Viticultural Development in the Douro Valley (ADVID) works as a unit of experimentation, offering services and training to meet the demands of the Douro’s vitiviniculturists.

Read More