Scientists have discovered how wine ‘breathes’ through the cork

A new study has shown that wine ‘breathes’ through the cork in not just one way, but several at once. First, oxygen is redistributed between the liquid and the air beneath the cork; then the cork itself releases oxygen; next, the oxygen reacts with substances in the cork; and, over a long distance, it gradually penetrates from the outside through the cork-neck system.

The study has been published in *Science Advances*.

The main conclusion is simple: the cork is not an absolute barrier against air, but rather a subtle regulator. A small amount of oxygen can help the wine develop, but an excess can lead to oxidation and a deterioration in flavour.

Details

To understand exactly how oxygen enters the bottle, French scientists created a miniature model of a wine bottle. They used glass tubes that replicated the shape and fit of a standard wine bottle neck, and sealed them with corks of varying lengths — ranging from short fragments to a standard cork measuring around 42 mm.

Some of the tubes were left empty, whilst others were filled with a model wine — a liquid containing malic acid to replicate the acidity of real wine. Glowing oxygen sensors were placed inside, allowing the researchers to monitor changes without removing the cork. The observations continued for up to 18 months.

This enabled the scientists to see that oxygen behaves differently at different stages of storage.

What happens after the bottle is sealed

In the first few hours after the bottle is sealed, oxygen is distributed between the liquid and the air space beneath the cork. This is a rapid phase: the system reaches equilibrium.

Then a slower process begins. The cork itself contains microscopic pores and air-filled cells. Over the course of months, it gradually releases oxygen into the bottle. According to the authors, this stage is largely complete after about nine months.

After this, substances from the cork begin to play an important role. Wood-derived compounds, including phenolic substances, can leach out of the cork and react with the oxygen in the liquid. In other words, the cork not only allows oxygen to pass through or is released, but also helps to ‘consume’ it chemically to some extent.

Over a longer period, however, oxygen from outside becomes the main factor. It slowly passes through the cork itself and across the microscopic boundary between the cork and the glass.

Why this matters for flavour

Oxygen is not always the enemy of wine. In small quantities, it can play a part in ageing and help the wine develop its aroma and flavour over time. But if there is too much oxygen, the wine can oxidise: the flavour will become flat, the colour will change, and the aroma will lose its freshness.

If there is too little oxygen, this isn’t always a good thing either. The wine may not develop as well and may develop undesirable odours. That is why balance is important for winemakers: how much oxygen enters the bottle, when exactly, and at what rate.

This is precisely why the cork matters. Different types of closures allow oxygen to pass through at different rates, and the interface between the glass and the cork can be a significant route for oxygen ingress. Previous research has shown that oxygen can pass not only through the stopper itself, but also through the interface between the cork and the neck of the bottle.

Why a cork is more than just a ‘stopper’

Conventionally, a cork is thought to be needed simply to seal a bottle. But when it comes to ageing wine, it plays a more complex role: it regulates the exchange with the external environment.

Oxygen ingress is influenced by the cork’s material, its length, how tightly it fits in the neck, its micropores, surface treatment, storage temperature and even the contact between the cork and the glass. Some studies on wine ageing show that the glass-cork interface can be an important pathway for oxygen transfer, and high storage temperatures intensify this process.

Put simply, a bottle of wine does not ‘stand still’ once it has been corked. A slow chemical process continues inside.

What this means for winemakers

The research helps winemakers select the most suitable cork for a specific wine. Some wines require more active oxygen exposure, whilst others need minimal contact. Some are intended for immediate consumption, whilst others are designed for years of ageing.

If we understand exactly how oxygen enters the bottle and when this happens, we can better manage the wine’s shelf life, flavour and the risk of oxidation.

This is particularly important for wines that are meant to be kept in the bottle for a long time. In such cases, even a slight difference in oxygen ingress over months and years can affect the final flavour.

Background

The term ‘breathes’ is used figuratively when referring to wine. A bottle does not breathe like a living organism, but oxygen exchange and chemical reactions do indeed take place inside it.

Winemakers have long known that oxygen is important at various stages of production and storage. It must be controlled during bottling, ageing and the storage of sealed bottles. Reviews on this topic identify dissolved oxygen as a critical parameter for wine quality after bottling.

This new study is valuable in that it has broken down this process into several mechanisms and shown that they operate over different timescales: hours, months and years.

Source

Study: Julie Chanut et al., “Deciphering the mechanisms of oxygen transfer into a wine bottle”, Science Advances, 2026.