Light strike (goût de lumière) - how light spoils wine in the bottle
Imagine that wine is spoiled not by cork, not by heat and not by time, but by the very light falling on the bottle on the shop shelf. This is not theory but a real, well-documented fault called light strike, in French goût de lumière. Wine in a clear bottle, exposed to a fluorescent lamp or sunlight, can within minutes take on unpleasant notes of rotten eggs, garlic and cooked cabbage. Two compounds naturally present in wine are to blame: riboflavin and methionine, which under light trigger a reaction producing foul sulfur compounds. Most at risk are rosé, sparkling and white wines in clear bottles. Here is what light strike is, how exactly it works, which wines are at risk and how to protect against it.
What light strike is
Light strike, or goût de lumière, is a wine fault arising from light falling on the bottle. The name comes from French and literally means taste of light, because it is exposure to radiation, not heat or oxygen, that causes this fault. The wine then takes on unpleasant sulfur aromas resembling rotten egg, garlic or cooked cabbage, and sometimes a metallic aftertaste appears. It is an insidious fault, because it can arise already on the shop shelf, before the bottle even reaches home. The key is to understand that the source of the problem is light reacting with components of the wine, not negligence in production or microbiological spoilage. Light strike is proof that wine is sensitive not only to temperature and oxygen, but also to radiation.
The mechanism: riboflavin and methionine
The heart of the whole phenomenon is a reaction between two compounds naturally present in wine. The first is riboflavin, that is vitamin B2, which acts as a photocatalyst: it absorbs light and enters an excited state. The second is methionine, a sulfur amino acid present in the wine. Riboflavin excited by light triggers the photo-oxidation of methionine, which leads to the breakdown of this amino acid and the formation of foul sulfur compounds. Science describes two variants of this reaction, but the essence is the same: light activates riboflavin, and it attacks methionine. Without light the reaction does not occur, which is why the fault arises only on exposure to radiation. Understanding this pair, riboflavin as the trigger and methionine as the victim, is the key to the whole topic. It is precise, verifiable chemistry, not magic.
What compounds form
The result of the photo-oxidation of methionine and cysteine in the presence of riboflavin is volatile sulfur compounds, the same ones responsible for the most off-putting smells in wine. Among them form hydrogen sulfide with its rotten-egg smell, methanethiol, dimethyl sulfide and dimethyl disulfide. It is precisely these compounds that give a wine affected by light strike its characteristic, unpleasant profile. They are volatile substances, perceptible even at low concentrations, which is why the fault can be pronounced. Importantly, these are exactly the same families of compounds responsible for the fault of reduction, though the path of their formation is different. Understanding that specific, named sulfur compounds stand behind light strike lets you speak about this fault precisely. It is not a mysterious defect but a predictable result of photochemistry.
How it smells
A wine affected by light strike has a very characteristic, recognisable smell. It is described as notes of rotten egg, garlic, onion and cooked cabbage, that is the typical bouquet of unpleasant sulfur compounds. Sometimes a metallic sensation in the taste is added. These aromas are foreign to wine and mute its natural, fruity character, leaving an impression of something stale and chemical. For the drinker it is a signal that something went wrong, though it is easy to confuse this fault with other sulfur defects. Recognising this specific cabbage-and-garlic profile helps diagnose that light was to blame. The longer the exposure, the more pronounced the fault. It is a smell that, once known, is hard to confuse with anything pleasant. Light strike reveals itself above all by the nose.
How fast it forms
The most surprising fact is how quickly light strike can form. The fault can develop after about sixty minutes of exposure to ultraviolet and some visible light. This means that a relatively short exposure of the bottle to strong light is enough to start the reaction. In practice the threat is prolonged standing under shop fluorescent lamps, in a window display or in a sunny spot. The longer and more intense the exposure, the more serious the fault. This speed makes light strike a real risk at every stage, from warehouse to shelf. Understanding that it is a matter of minutes and hours, not weeks, underlines how important it is to protect wine from light. It is a fault that needs not time but only exposure.
Why the clear bottle is to blame
A key risk factor is the colour of the bottle, specifically its transparency. Colourless, clear glass barely protects wine from radiation, letting through the light that triggers the reaction. Producers often choose clear bottles precisely to show off the colour of the wine, especially appetising rosé or golden white. It is an aesthetic marketing decision that nonetheless exposes the wine to light strike. Dark glass, green or brown, absorbs much of the harmful radiation and protects the contents far better. That is why wines in dark bottles are safer, and those in clear ones more at risk. Understanding this relationship explains why certain categories of wine fall victim to this fault more often. A clear bottle is beauty at the cost of protection.
Which wines are most at risk
Not all wines are equally at risk, and the difference stems mainly from packaging and wine type. Most at risk are rosé and sparkling wines, and also whites, especially those bottled in clear glass. The reason is twofold: producers of these wines often choose colourless bottles to display the colour, and the wines themselves can be delicate and poor in natural protection. White varieties such as chardonnay or pinot gris can develop the fault after just two or three weeks of exposure. Red wines are less at risk, because their tannins and pigments act protectively, and the bottles are usually dark. This shows that the risk of light strike is a combination of wine type and glass colour. Rosé in a clear bottle is a classic example of the threat.
The secondary reaction and browning
Light strike is not only sulfur smells, because light also triggers another, accompanying reaction. Radiation reacting with the tartaric acid in wine leads to the formation of glyoxylic acid and hydrogen peroxide. These compounds can make the colour of a white wine change, darkening toward yellow or brown. This means a wine affected by light strike can be not only foul-smelling but also visually altered. Browning of the colour is an additional signal that the wine has suffered from radiation. Although the main fault is the sulfur compounds, this secondary reaction shows how multifariously light harms wine. Understanding that light attacks wine in several ways at once underlines the scale of the problem. It is a fault visible both in the nose and in the colour.
How producers protect wine
Producers have several ways to protect wine from light strike. The simplest and most effective is using dark glass, green or brown, which absorbs harmful radiation. The second route is chemical protection of the wine’s composition: studies indicate that glutathione, sulfur dioxide and hydrolysable tannins act protectively, limiting the development of the fault. Some producers also reach for opaque packaging or wraps that limit light access. Choosing a clear bottle for visual effect is a deliberate risk that must be balanced by other safeguards or rapid stock turnover. Understanding these methods shows that light strike is a fault that can be prevented already at the production and packaging stage. Protection from light is a real, technical decision of the winemaker.
How to protect wine at home
At home too you can reduce the risk of light strike with a few simple habits. Above all it is worth storing wine, especially in clear bottles, away from light: in a dark cupboard, cellar or box, not on a sunny windowsill or under a bright lamp. Wines in colourless glass, like rosé or sparkling, are best bought fresh and not kept long in the light. If a shop stores wine under strong fluorescent lamps for a long time, it is worth bearing in mind for delicate whites and rosés. If you want to deliberately follow how storage conditions affect wine, record your observations in the app and compare your impressions. A little caution with light exposure really protects delicate wines from this fault.
Light strike versus reduction
Light strike is easy to confuse with another sulfur fault, namely reduction, because both give similar smells. The difference lies in the cause: reduction arises from a lack of oxygen during production and maturation, while light strike arises only under radiation, already in the bottle. Both faults give sulfur compounds smelling of egg, garlic or cabbage, so by the nose alone they can be indistinguishable. A clue may be the context: if a wine in a clear bottle stood in the light, suspect light strike. It is worth knowing both faults to understand where the sulfur notes in the glass come from. You can read more about the related fault and how to recognise sulfur defects in the post on reduction and oxidation. Light strike is a sulfur fault of light, not oxygen, origin.
The key points
Light strike, or goût de lumière, is a wine fault arising from light falling on the bottle. The mechanism is precise: light excites riboflavin (vitamin B2), which photo-oxidises the sulfur amino acid methionine, giving foul volatile sulfur compounds, like hydrogen sulfide, methanethiol and sulfides smelling of rotten egg, garlic and cooked cabbage. The fault can form after about an hour of exposure, and the clear bottle, which does not protect from radiation, is usually to blame. Most at risk are rosé, sparkling and white wines in colourless glass; chardonnay and pinot gris can suffer after just two or three weeks. Light also reacts with tartaric acid, browning the colour. Protection comes from dark glass and from glutathione, sulfur dioxide and tannins, and at home from storage away from light. It is a sulfur fault of light origin, easy to confuse with reduction.