Oxidation is one of the concepts worth understanding when enjoying wine.
For producers, oxidation is an important subject, but drinkers should not ignore it either.
At the same time, if beginners think about oxidation in an overly complicated way, wine can start to feel less like an enjoyable drink and more like a difficult one.
This article explains wine oxidation in straightforward terms for beginners.
Simply understanding the relationship between wine and oxidation can change the way you handle and enjoy wine.
What Is Oxidation?
In chemistry, oxidation is defined as a reaction in which a substance loses electrons.
But electron transfer is invisible to us, so for most people, hearing that “oxidation is a reaction in which electrons are lost” does not make the idea feel especially intuitive.
For example, cut an apple in half and leave it exposed: the cut surface gradually turns brown. Oxidation is involved in that reaction.
Oxidation affects aromas, flavors, pigments and many other components in food. For foods valued for freshness and appealing aromas, it is generally regarded as undesirable.
So what does oxidation mean in wine?
Wine Oxidation
Put simply, wine oxidation refers to chemical reactions in wine that occur when it comes into contact with oxygen in the air.
Imagine opening a fresh, fruity white wine, pouring it into a glass and leaving it for several hours.
Its clear appearance may turn somewhat brownish, the aromas may fade and the flavor will likely change.
Oxygen in the air reacts with phenolic compounds and other components in the wine. Through a series of chemical reactions, acetaldehyde can be produced, a compound associated with apple-like aromas.
This component is considered to be related to browning and distinctive oxidative flavors. As a result, a fresh and fruity white wine can lose the qualities that originally made it appealing.
For wines in which fresh-fruit aromas are especially important, protection from oxidation matters both before and, in particular, after opening.
White Wine Requires More Attention Than Red
Most people can imagine that wine left in a glass or an opened bottle for too long will deteriorate in flavor.
Contamination can of course alter the taste, but many changes, including changes in aroma, are related to oxidation.
Red and white wines, however, appear to respond differently to oxidation.
Wine contains many kinds of phenolic compounds, some of which are thought to help inhibit oxidation mechanisms.
Red wine is made by fermenting skins, seeds and juice together and therefore contains abundant phenolic compounds. Typical white wine, by contrast, is fermented mainly from juice and contains fewer phenolics.
It is not entirely clear which phenolic compounds are responsible for protecting wine from oxidation, but white wines, with their lower phenolic content, are generally considered more susceptible to oxidation than red wines.
If you plan to finish a wine the same day, you therefore may not need to worry quite as much about oxidation with red wine—although opened red wine should still be handled carefully.
What Drinkers Should Keep in Mind About Oxidation
As a general rule, wine should be protected from oxidation as much as practical.
That said, some wines become more appealing through oxidative aging, and deliberately exposing older vintages to oxygen can sometimes help alter reductive aromas. So “oxidation equals bad” is not universally true.
For ordinary everyday wines, however, minimizing oxidation is generally a good approach.
Here are a few points drinkers should know.
Take Particular Care with Sauvignon Blanc and Similar Wines
Even among wines, susceptibility to oxygen varies.
For example, the characteristic aromas of Sauvignon Blanc are considered particularly sensitive to oxidation.
The striking aromas associated with Sauvignon Blanc—pineapple, grapefruit, fresh herbs and tropical fruit—are related to compounds known as polyfunctional thiols.
These polyfunctional thiols oxidize easily and can be affected relatively soon after the bottle is opened.
Polyfunctional thiols are not unique to Sauvignon Blanc; they are found in a variety of grapes, including Koshu.
You may not always be able to research these compounds in advance, but when buying wine, consider asking knowledgeable staff and paying attention to whether the wine depends heavily on thiol-derived aromas.
Storage Conditions
Wine is not affected by oxidation only after a bottle is opened or poured into a glass.
For storage, synthetic closures, screw caps and high-quality wine stoppers designed to limit oxidation can reduce oxygen ingress compared with some natural cork closures.
Another factor that is surprisingly easy to overlook is storage temperature.
One study suggested that the higher the temperature at which bottles were stored, the faster the rate of oxidation.
That makes it worth paying attention not only to where wine is stored at home but also to the conditions in which it is displayed and sold at a shop. Wines transported for long periods by ship may likewise be more exposed to oxidation-related risks.
When buying and storing wine, consider both the retail environment and the conditions in which you will keep the bottle afterward.
Summary
For beginners, wine oxidation can feel like something they almost understand but cannot quite explain.
Start with one simple idea: when wine comes into contact with oxygen in the air, chemical changes occur that can alter its aroma and color.
From there, it becomes easier to understand how oxidation develops, which grape varieties are particularly susceptible and how wine should be stored.
We hope this article becomes one useful piece of knowledge you can bring into your own wine life.