Wine Oxidation Research Articles

Oxidation in white wine: The point of view of winemakers from areas with different oenological practices

Oxidation in white wine: The point of view of winemakers from areas with different oenological practices

Wine polyphenol oxidation mechanism and the effects on wine quality: A review.

Over the last few decades, there has been considerable interest in studying wine oxidation. This review paper provides a comprehensive overview and analysis of the molecular changes caused by oxidation in wine and how they affect wine quality. Simultaneously, the recent advancements in understanding the molecular pathways involved in wine oxidation are also discussed. The paper first explores the process of oxygen dissolution and the complex transformations that occur in polyphenols during oxidation. It then reviews the current methods of micro-oxidation (MOX) and over-oxidation (OOX). Subsequently, it introduces oxidation kinetics, and controls indexes for the degree of oxidation and the underlying principles. Additionally, it discusses the effects of oxidation on the sensory qualities of wine and analyzes the interrelationships between oxidation, functional components, and drinkability. The comprehensive review of the literature shows that OOX leads to the rapid depletion of polyphenols, reducing the overall antioxidant capacity of the wine and affecting its appearance and flavor. In contrast, MOX promotes a balanced matrix and enhances the complexity of the aroma. Polyphenols, particularly resveratrol, can interact with reactive oxygen species or activate endogenous defense mechanisms to mitigate diseases risks. However, the presence of oxygen can activate the antioxidant mechanism of resveratrol, resulting in decreased content and a diminished anti-disease effect. Despite this, a clear distinction between OOX and MOX has not been established. Future research should focus on identifying and defining precise oxidation levels using control indexes for the degree of oxidation.

Toward a rational approach for polyphenol usage in the shelf-life extension of oenological products

The durability of food items, i.e. their shelf life, plays a crucial role in optimizing their quality and exploitation with the aim of limiting food and beverage waste. The primary factor contributing to prolonged deterioration is the oxidation of food products, leading to the generation of by-products that compromise their sensory qualities, such as off-flavors and organoleptic features in general. Concerning beverages, and wine in particular, polyphenols from wood and grapes extracts have gained significant popularity as natural agents able to preserve the quality and desired features due to their recognized antioxidant and anti-radical properties. Although the ability of oak to release polyphenols able to enhance the long-term stability of wines is widely acknowledged, effective methods for monitoring both their kinetics of oxidation and browning are still lacking. A spectrophotometric approach was exploited to develop a novel method for monitoring wine oxidation in the attempt of filling the gap. Such approach was successfully applied to track qualitatively the aging kinetics in oxidative conditions using a wine simulant with the addition of 16 natural extracts. Chestnut and oak extracts resulted the most performing in both hue conservation and oxidized species limitation. Principal component analysis demonstrated that polyphenol of different class can be recognized even after 30 days of oxidation, thus suggesting potential applications of the method in quality and conformity control of polyphenol extracts. The results allow a rational choice of the best polyphenol extract for each specific application in wines, with potential application to other beverages and foods.

Copper (II) Level in Musts Affects Acetaldehyde Concentration, Phenolic Composition, and Chromatic Characteristics of Red and White Wines.

Copper (II), a vital fungicide in organic viticulture, also acts as a wine oxidation catalyst. However, limited data are currently available on the impact that maximum allowed copper (II) ion doses in wine grapes at harvest can have on aged wine quality. This was the focus of the present study. We investigated the copper (II) effects by producing both white and red wines from musts containing three initial metal concentrations according to the limits set for organic farming. In detail, the influence of copper (II) on fermentation evolution, chromatic characteristics, and phenolic compounds was evaluated. Interestingly, the white wine obtained with the highest permitted copper (II) dose initially exceeded the concentration of 1.0 mg/L at fermentation completion. However, after one year of storage, the copper (II) content fell below 0.2 ± 0.01 mg/L. Conversely, red wines showed copper (II) levels below 1.0 mg/L at the end of fermentation, but the initial copper (II) level in musts significantly affected total native anthocyanins, color intensity, hue, and acetaldehyde concentration. After 12-month aging, significant differences were observed in polymeric pigments, thus suggesting a potential long-term effect of copper (II) on red wine color stability.

The Role and Application of Redox Potential in Wine Technology

In wine technology, the on-line measurement of redox potential is a fast, accurate, and reliable measurement that provides insight into the metabolism of Saccharomyces cerevisiae, its microbial activity, and the oxidation and reduction state of wine, as well as insight into its quality and stability. The significance of the redox potential measurement and control in wine technology as well as the maintenance and regulation of fermentation redox potential using temperature and carbon dioxide fluxes are discussed. Redox potential levels from Eh 100 to 180 mV are typical for non-oxidized wine that is bottling-ready, while levels of Eh 270 to 460 mV represent oxidized wines with typical failures. The relevance of redox potential measurement during the 2-year maturation of Blau Fränkisch wine in 225 L oak barrels at six levels at a temperature 15 °C is presented. The measurement of the redox potential, expressing heterogeneity in redox layers during wine maturation in oak barrels, is represented in various oxido-reductive fermentation zones. On the contrary, the end of the maturation process is indicated by the homogeneity of redox zones, where the matured wine shows no differences in redox measurement on all levels. Using redox potential as a key scale-up criteria ensures comparable and reproducible amounts of the final product even in geometrically non-similar fermenter systems.

Mechanisms of the initial stage of non-enzymatic oxidation of wine: A mini review.

Non-enzymatic oxidation is a primary factor affecting wine quality during bottling or aging. Although red and white wines exhibit distinct responses to oxidation over time, the fundamental mechanisms driving this transformation remain remarkably uniform. Non-enzymatic oxidation of wine commences with the intricate interplay between polyphenols and oxygen, orchestrating a delicate redox dance with iron and copper. Notably, copper emerges as an accelerant in this process. To safeguard wine integrity, sulfur dioxide (SO2) is routinely introduced to counteract the pernicious effects of oxidation by neutralizing hydrogen peroxide and quinone. In this comprehensive review, the initial stages of non-enzymatic wine oxidation are examined. The pivotal roles played by polyphenols, oxygen, iron, copper, and SO2 in this complex oxidative process are systematically explored. Additionally, the effect of quinone formation on wine characteristics and the intricate dynamics governing oxygen availability are elucidated. The potential synergistic or additive effects of iron and copper are probed, and the precise balance between SO2 and oxygen is scrutinized. This review summarizes the mechanisms involved in the initial stages of non-enzymatic oxidation of wine and anticipates the potential for further research.

Targeted 1−H-NMR wine analyses revealed specific metabolomic signatures of yeast populations belonging to the Saccharomyces genus

This study aimed to explore the non-volatile metabolomic variability of a large panel of strains (44) belonging to the Saccharomyces cerevisiae and Saccharomyces uvarum species in the context of the wine alcoholic fermentation. For the S. cerevisiae strains flor, fruit and wine strains isolated from different anthropic niches were compared. This phenotypic survey was achieved with a special focus on acidity management by using natural grape juices showing opposite level of acidity. A 1H NMR based metabolomics approach was developed for quantifying fifteen wine metabolites that showed important quantitative variability within the strains. Thanks to the robustness of the assay and the low amount of sample required, this tool is relevant for the analysis of the metabolomic profile of numerous wines. The S. cerevisiae and S. uvarum species displayed significant differences for malic, succinic, and pyruvic acids, as well as for glycerol and 2,3-butanediol production. As expected, S. uvarum showed weaker fermentation fitness but interesting acidifying properties. The three groups of S. cerevisiae strains showed different metabolic profiles mostly related to their production and consumption of organic acids. More specifically, flor yeast consumed more malic acid and produced more acetic acid than the other S. cerevisiae strains which was never reported before. These features might be linked to the ability of flor yeasts to shift their metabolism during wine oxidation.

ИССЛЕДОВАНИЕ СКЛОННОСТИ ФЕНОЛЬНЫХ ВЕЩЕСТВ ВИНОМАТЕРИАЛОВ И ВИН ИЗ ВИНОГРАДА СОРТА КАБЕРНЕ СОВИНЬОН К ОКИСЛЕНИЮ

One of the most important tasks in the production of high-quality red wines is the preservation of intense color, which exposed to atmospheric oxygen, can change and acquire garnet or brown shades. The intensity of color, its shades and stability are determined by the presence of phenolic compounds in wine, among which polymeric forms of polyphenols and anthocyanins have a rich color. In addition, the phenolic substances of red wines are represented by monomeric forms, catechins and procyanidins, etc. The impact of oxygen at various stages of the technological process of making wine can have both positive and negative effects on its chemical composition and organoleptic characteristics. The purpose of this research was to study the effect of oxygen introduced at various technological stages of the preparation of wine materials. As a result of studies of the indicators of the mass concentration of oxygen and phenolic substances that cause wine oxidation, as well as the organoleptic indicators of dry red wines (production samples) made from the Cabernet Sauvignon grape variety in various geographical zones of southern Russia, significant differences have been revealed due to agro-climatic conditions of growing grapes in a particular area, as well as the grape processing technology used at enterprises. Under the conditions of the laboratory and production unit «Micro wine-making», the possibility of using the microoxidation method both at the stage of must and pulp fermentation, and after the fermentation process (stabilization and clarification) for the purpose of deliberate oxidation of polyphenols, was shown. Based on the conducted studies, the optimal dosage of exogenous oxygen, which has a positive effect on the organoleptic characteristics of wine materials, is a concentration of 4-6 mg/dm3 both during microoxidation at the stage of must and pulp fermentation, and at the end of the fermentation of wine.

Oxidation of Wine Polyphenols by Electrochemical Means in the Presence of Glutathione.

The oxidation of wine may be beneficial or harmful to its quality. On the one hand, controlled oxidation can lead to the development of desirable sensory characteristics for red wine, such as enhanced color stability. Alternatively, oxidation can lead to white wine browning and a decrease in fruity aromas, and the development of an off flavor and wine polyphenols are also involved. The presence of glutathione (GSH) can help mitigate the negative effects of oxidation by acting as a protective antioxidant. In order to better understand the antioxidant role played by GSH, wine polyphenols oxidation experiments by electrochemical means in the presence of GSH were carried out. The oxidation behavior of polyphenols representing different phenolic classes commonly found in wines, including protocatechuic acid (PCA), caffeic acid (CAF), epicatechin (EC), and rutin (Ru), was investigated using cyclic voltammetry and bulk electrolysis. We identified the oxidation products and reaction pathways of these polyphenols using ultra-high-performance liquid chromatography coupled with mass spectrometry (UPLC-MS), in both the absence and the presence of glutathione (GSH). UPLC-MS was utilized to demonstrate that, in the presence of glutathione (GSH), the four molecules were subjected to electrochemical oxidation, resulting in the formation of mono- and bi-glutathione conjugates. A two-electron oxidation process combined with the removal of two protons is the first step in transforming polyphenol molecules. As a result, the corresponding quinone is formed. The quinone can then be reduced back to its original form by glutathione (GSH), or it can interact further with GSH to produce mono- and bi-glutathione conjugates. These results contribute to understanding and predicting the oxidative degradation pathway of polyphenols in wine. Understanding this process seems important for winemakers to control and optimize the sensory characteristics of their wines.

Effect of chitosan addition on acetaldehyde and polymeric pigments production after oxidation of red wines with different tannin/anthocyanins ratio

In order to evaluate the effect of the application of chitosan to red wines with different initial composition, four wines showing tannins/anthocyanins ratio (T/A) ranging from 0.15 to 2.44 were treated with this amino polysaccharide. As one of the main factors involved in red wine ageing is the oxidation, even a forced oxidation test was applied on all the samples. The addition of chitosan determined a decrease in total phenolic compounds mainly due to the adsorption of protein-reactive tannins which decreased from 10 to 50% of the initial value. The previous addition of chitosan determined a lower production of acetaldehyde after oxidation confirming the antioxidant activity of this amino polysaccharide. The production of acetaldehyde was lower in samples with a higher T/A ratio probably due to the involvement of acetaldehyde in reactions with flavanols and anthocyanins giving polymeric pigments. These results suggest a possible use of chitosan in red wine with a higher T/A ratio to decrease the content of tannins reactive towards proteins and, contemporary, to act as antioxidant.

Yeast derivatives: a promising alternative for white wine oxidation prevention

In the previous decade, the use of Yeast Derivatives (YD) was proposed as a new strategy to control wine oxidation (Comuzzo et al., 2015). These products are obtained from yeasts by autolytic or hydrolytic processes and then dried to obtain the commercial products. The aim of this work was to carry out a preliminary investigation of commercial YDs with different compositions in order to (i) compare their capacity to prevent white wine oxidation in comparison with conventional treatment using SO2, and (ii) evaluate their impact on wine quality.

The Application of Non-Thermal Technologies for Wine Processing, Preservation, and Quality Enhancement

Recently, non-thermal wine processing technologies have been proposed as alternatives to conventional winemaking processes, mostly with the aims to improve wine quality, safety, and shelf-life. Winemakers typically rely on sulfites (SO2) to prevent wine oxidation and microbial spoilage, as these processes can negatively affect wine quality and aging potential. However, SO2 can trigger allergic reactions, asthma, and headaches in sensitive consumers, so limitations on their use are needed. In red winemaking, prolonged maceration on skins is required to extract enough phenolic compounds from the wine, which is time-consuming. Consequently, the wine industry is looking for new ways to lower SO2 levels, shorten maceration times, and extend shelf life while retaining wine quality. This review aggregates the information about the novel processing techniques proposed for winemaking, such as high-pressure processing, pulsed electric field, ultrasound, microwave, and irradiation. In general, non-thermal processing techniques have been shown to lead to improvements in wine color characteristics (phenolic and anthocyanin content), wine stability, and wine sensory properties while reducing the need for SO2 additions, shortening the maceration time, and lowering the microbial load, thereby improving the overall quality, safety, and shelf life of the wines.

Targeting iron speciation in wines: Design of a microfluidic paper-based device for determination of iron(II) and iron(III)

During the winemaking process, wine is frequently exposed to oxygen which can affect the organoleptic characteristics and therefore the quality of the finished wine. Most phenolic molecules in wine serve as oxidation substrates affecting colour and flavour. Transition metal ions namely copper and iron act as electron pumps; in fact, Fe(III) is reduced to Fe(II) as a consequence of the oxidation of phenols to quinones and, in the presence of oxygen, Fe(II) is oxidised back to Fe(III). Consequently, speciation analysis by the oxidation state is critical and even more relevant than the total ion concentration when one wants to evaluate the risk for wine oxidation. Interestingly the different reactivity of Fe(III) and Fe(II) makes spectrophotometric methods, namely colorimetric reactions, ideally suited for speciation analysis. In this work, a microfluidic paper-based analytical device (µPAD) was designed for the iron speciation in wine samples. The colorimetric reaction between bathophenanthroline and iron(II) was chosen and the oxidation of Fe(III) to Fe(II), using hydroxylamine, was carried out within the same device. Aiming for application to different types of wine, the developed device also enabled to account for the potential sample colour (subtraction of interfering signal). The designed µPAD enabled the iron speciation in both white and red wines.

Prevention of browning development in white wine by Se addition

Oxidation of white wines implies modification of their organoleptic characteristics and in most cases degradation of their overall quality. The development of oxidative browning is associated with polyphenol oxidation, and it can be accelerated by the presence of metal ions such as Fe2+ while it may be delayed by the addition of antioxidants, such as selenium (Se) and SO2. The aim of this study was to study the browning capacity of Assyrtiko white wines after Se addition at two temperatures (35 and 50°C) employing the accelerated browning test. For this purpose, two concentrations of Se were added at the wine, either alone or with the simultaneous presence of Fe2+, and the absorbance at 420 nm was monitored for twelve days. It was also of interest to evaluate the changes of other analytical parameters which are implicated in wine oxidation such as: SO2 content (free and total). Browning was approached from a kinetic point of view and the study was focused on the implication of oxidants and antioxidants on browning rate. The results showed that the addition of Se protected wine color and preserved total SO2 at 35°C while at 50°C these effects were not any longer observed. GSH content of the samples containing Se after 12 days of accelerated ageing was similar with that of the control.

Metabolomics Integrated with HPLC-MS Reveals the Crucial Antioxidant Compounds of Muscadine Wine.

Wine is a kind of beverage with a variety of compounds beneficial to human health, which makes it popular all over the world and it contributes importantly to economics. The excessive oxidation of wine has always been a major problem in wine production and storage. Unlike traditional wines which are made from Eurasian grapes, wines made from muscadine grapes (Muscadinia rotundifolia Michx.) can maintain their sensory qualities under natural oxidation conditions for relatively long periods of time despite the insight mechanisms still being unclear. In this study, two muscadine wines, Carlos (CAL) and Noble (NOB), and two traditional wines, Chardonnay (CH) and Marselan (MAS), were chosen for comparison of their compositional alteration during oxidation, in order to analyze the principal components contributing to the antioxidant characteristics of muscadine wines. The DPPH, ORAC, color intensity, and total phenolic content changes during the natural oxidation process were analyzed. Six core significantly changed metabolites (SCMs, avicularin, beta-lactose, delphinidin-3-O-glucoside, ellagic acid, myricetin, and 4-methylcatechol [p < 0.05]) related to the oxidation process were determined. In addition, HPLC-MS was also used to identify pyrogallol which is a unique antioxidant compound in muscadine wine. The present work aims to reveal the crucial antioxidant compounds of muscadine wine and provide valuable information and a new platform for future research on wine oxidation.

Impact of the Closure Oxygen Transfer Rate on Volatile Compound Composition and Oxidation Aroma Intensity of Merlot and Cabernet Sauvignon Blend: A 10 Year Study

This study evaluated the impact of closure type on unoaked 100 %-Merlot, oak-aged 70%-Merlot/30%-Cabernet Sauvignon, and 30%-Merlot/70%-Cabernet Sauvignon during a 10 year period. Closures were microagglomerate corks, screw caps, and synthetics with the known oxygen transfer rate (OTR), ranging from 0.1 to 4.6 mg/y, including natural corks. Oxidation intensity perception, dissolved oxygen, sulfite, and 3-methyl-2,4-nonanedione (MND) were monitored on a regular basis. After 10 years of aging, additional aroma impact markers were evaluated (3-sulfanylhexan-1-ol, H2S, DMS, methional, and phenylacetaldehyde). Low OTR levels (≤0.3 mg/y) delayed the oxidation of red wines in this long-term experiment. In addition, our results led us to hypothesize that the MND concentration in young wines might be linked with their ability to produce it during bottle aging that is with their aging potential. Finally, we found that the kinetic accumulation of MND in wines was first strongly impacted by its intrinsic composition and thereafter by the OTRT0 of the stopper.

Influence of Oxygen Management during the Post-Fermentation Stage on Acetaldehyde, Color, and Phenolics of Vitis vinifera L. Cv. Cabernet Sauvignon Wine.

Oxygen exposure is unavoidable and the impact of its management during the post-fermentation stage (PFS) on dry red wine is poorly investigated. This study was dedicated to the variation of acetaldehyde, color and phenolics of Cabernet Sauvignon dry red wine during five discontinuous oxidation cycles of four levels of controlled oxygen supply, which were carried out to simulate probable oxidation during the PFS. Free SO2 disappeared after the first, second and third oxidation cycles in wines with high, medium and low levels of oxygen exposure severally, but subsequent oxygen exposure below or equal to 2 mg O2/L per cycle had little effect while 3–3.9 mg O2/L per cycle dramatically facilitated acetaldehyde accumulation, which was accompanied by an enormous variation in color and pigments, especially when total oxygen consumption was above 10 mg/L. The utilization of clustered heatmap and partial least square regression demonstrated the feasibility of characterization of wine oxidation degree using the chemical parameters measured by UV-spectrophotometry. Oxygen exposure during the PFS should be emphatically controlled, and chemical indexes determined by the UV–spectrophotometric method can be used for a scientific and effective description of wine oxidation degree.

Wine Closure Performance of Three Common Closure Types: Chemical and Sensory Impact on a Sauvignon Blanc Wine

A Napa Valley Sauvignon blanc wine was bottled with 200 each of a natural cork, a screw cap, and a synthetic cork. As browning is an index for wine oxidation, we assessed the brown color of each bottle with a spectrophotometer over 30 months. A random-effects regression model for longitudinal data on all bottles and closure groups found a browning growth trajectory for each closure group. Changes in the wine’s browning behavior at 18 months and 30 months showed that the browning of the wine bottles appeared to slow down later in the storage period, especially for natural corks. The between-bottle variation was the highest for the natural cork. At 30 months, we separated the bottles by the extent of browning and samples were pulled from the high, mid, and low levels of browning levels for each closure. The degree of browning is inversely correlated with free SO2 levels ranging from 5 to 12 mg/L. However, a Quantitative Descriptive Analysis (QDA™) sensory panel could not detect any difference in their aroma and flavor profile between closure types regardless of browning level. Even low levels of free SO2 retain protection against strong oxidation aromas, and visual browning detected by spectrophotometer seemed to precede oxidative aroma and flavor changes of the aging Sauvignon blanc.

Alternative Perspective on Rapid Wine Oxidation through Changes in Gas-Phase Volatile Concentrations, Highlighted by Matrix Component Effects

A new perspective is presented to investigate the sensorially relevant gas-phase concentrations of volatile compounds in wine. This is achieved by measuring the partition coefficients and matrix-phase concentrations of volatiles using static headspace-gas chromatography-ion mobility spectrometry. Physicochemical properties that can contribute to the partition behaviors of 10 volatile esters, such as hydrophobicity and matrix temperature, are also discussed. Partition coefficients are then linked to quantitative measurements to obtain partial pressures, which describe the availability of volatile compounds in the gas phase. The concept of partition coefficients and partial pressure has then been applied to a time series of aroma changes due to oxidation in commercial wines. As a follow-up study, a full factorial design was devised to inspect the impact of three common wine matrix components, namely, copper, polyphenols, and ascorbic acid, on the partial pressure changes after 30-day oxidation treatment in either full-alcohol or low-alcohol simulated wine matrices. Interesting interactive effects between antioxidant behaviors and alcohol levels were elucidated, especially around the controversial use of ascorbic acid in winemaking. These results can guide winemakers who wish to minimize oxidative damage to wine aroma during wine storage or bulk transport, where ullage may be present or continual oxygen ingress may be occurring.

Factors That Affect the Accumulation of Strecker Aldehydes in Standardized Wines: The Importance of pH in Oxidation.

Strecker aldehydes (SA) can be formed in wine from the degradation of Strecker and, to a lesser degree, via the oxidation of higher alcohols. The objective of this article is to assess the magnitude of the differences introduced by wine compositional factors other than amino acids and Fe, in the accumulation of SA during oxidation. Eight red, two rosé and two white wines were oxidized. The accumulation of SA was analyzed. Whites and rosés presented negative accumulations for isobutyraldehyde, and in general, these wines accumulated smaller concentrations of the other SA than red wines. Only methional and phenylacetaldehyde were accumulated in all of the wines during oxidation. 2-methylbutanal and 3-methylbutanal were accumulated in 9 out of the 12 wines, whereas isobutyraldehyde was accumulated only in 5 out of the 12. 2-methylbutanal was, on average, the least accumulated aldehyde. Methional was the aldehyde formed most homogenously. Most of the observed differences can be attributed to three factors: the pH, oxidation time and native levels of Strecker aldehydes. The influence of pH was particularly intense in the cases of phenylacetaldehyde and methional. An independent test using synthetic wines with Strecker amino acids and 4-methylcatechol with different pHs (4.2, 3.5 and 2.8) was carried out in order to verify the higher pH value, the greater accumulation in SA after oxidation process. The results strongly suggest the important role played by pH in the accumulation of SA in wine oxidation.