This article features everything you need to know about the wine fault lightstrike: how it happens, how to prevent it, and most importantly how to recognize it so you can return the affected bottle back before you drink it.
Lightstrike in a nutshell
- in the early formation of lightstrike development, only the primary fruit is missing from the aromas. This makes it really difficult to spot
- then it develops stinky aromas of dishwater, cooked cabbage, wet wool, onion, egg, damp cardboard or sewage
- most wines have no colour change at all – again making this common fault difficult to spot
- but colour may be dull
- or worse, wines may turn yellow or brown tinged
- in the early formation of lightstrike development, only the primary fruit is missing from the flavours. This makes it really difficult to spot
- then it develops awful flavours just like the aromas on the nose: dishwater, cooked cabbage, wet wool, onion, egg, damp cardboard or sewage
How wines get lightstrike:
- wines in bottle get lightstrike simply by sitting under light
- this means that wines can be tainted in the bottling line, on your countertop or on supermarket shelves
The types of wine that are most susceptible:
- sparkling wines, white wines and pale rosé wines are especially susceptible to UV light
- wines that are in clear glass bottles
How to prevent lightstrike:
- store your wines in a cool dark place (like a basement cellar).
- Read SommTips below for ways to reduce the likelihood you’ll buy a bottle ruined by lightstrike
Lightstrike, the complete story...
The science of how lightstrike occurs...
Lightstrike occurs when wines are exposed to too much UV light and/or blue light. When this happens, the wine produces volatile sulphur compounds which are smelly smells.
For those of you who like detail, it’s like this…
Light reacts with riboflavin in the wine and photo-oxidizes methionine (a sulphur-containing amino acid also present in wine). When this happens undesirable sulphur compounds such as dimethyl disulfide (or DMDS for short) are formed.
A secondary reaction can also see light react with tartaric acid in wine to form glyoxylic acid and hydrogen peroxide. This response contributes to the accumulation of yellow and brown pigments and changes the wines’ colour. In both cases, the effect is irreversible.
[But here are some excellent tasting notes! Here are 10 Champagnes and Bubbles on a Budget.]
Are wines affected by lightstrike harmful?
The answer is no. Wines that are affected by lightstrike are not harmful to you at all. At low levels, they are just not as pleasurable to drink – leaving you without a lasting impression or reason to buy it again. At higher levels, the wine will totally stink (see below).
How to spot lightstrike at high levels...
It’s pretty easy to spot faulted wines when they are badly affected by lightstrike. The wines can smell and taste of cooked cabbage, onion, smelly cheese, damp cardboard or raw sewage.
[Note: Wines affected by lightstrike can also smell of wet wool. But make sure you don’t confuse the wet wool of lightstrike with wines that are supposed to smell like wet wool. Wines made from Chenin Blanc have a wet wool aroma from the grape variety. Therefore, Chenin Blanc from South Africa or bottles that say Vouvray, or Savennières from the Loire Valley are known for their aromas and flavours of of wet wool.
How to spot lightstrike at low levels...
At low levels, lightstrike does the same thing as most other wine faults. It cancels out the fruit.
Here’s why that’s tricky to spot. You have to know what the fruit of the wine is supposed to taste like before you know it’s missing.
With delicate flavoured wines such as Champagne, this is really difficult to do. You need to seek those soft fruit aromas and flavours of lemon juice, lemon curd, or apple/ quince fruit.
But it’s trickier than this.
Because when the wine is faulted, you will still be able to taste the winemaking or secondary aromas and flavours. In Champagne, that means you’ll smell and taste the struck match aromas, light toast, brioche, or freshly baked bread aromas from the autolysis winemaking process. You will also be able to taste the light almond nuttiness in the mid-palate and yeast from the lees ageing.
Still, that lemon juice, lemon custard and apple/ quince fruit will be missing.
Other secondary aromas that will fool you into thinking the wine is not faulted are the aromas and flavours from oak ageing the wine in neutral or toasted barrels. Aromas and flavours such as yogurt, nutmeg, cinnamon, and clove baking spices will show through nicely when a wine has low levels of lightstrike.
It’s common then for people to assume that they just don’t like the wine. You really must train yourself to question and ask, “Do I not love this wine because of me or is it possible that there is something off about this wine?” Then ask yourself, “Can I smell and taste the fruit aromas?”
To know which fruit aromas you are supposed to smell, do a quick search for tasting notes of the wine in an app like Vivino, Delectable and Cellar Tracker.
I’d argue that when a wine is only slightly tainted, it’s easier to spot lightstrike when you put the wine in your mouth and taste it. At first, the wine will simply lack any oomph. Upon closer questioning, you can discern that it is the primary fruit flavours that are missing, causing the wine to have no zest, no completeness, no balance.
Try this test at home...!
If you do this test, let us know in the comments section what you discovered!!
Which wines are most affected by lightstrike?
Red wines are least likely to be affected by lightstrike. That’s because red wines have tannin, an essential molecule that helps red wines age well and last.
As most white wines lack tannin, they are much more susceptible to UV light than their beefy red counterparts. Furthermore, those pretty pale coloured rosé wines, are highly susceptible to lightstrike as they have very little contact with grapeskins and very little tannin and tend to oxidize quickly.
In fact, lightstrike most often affects white and rosé sparkling wines. The off-aromas and flavours produced by lightstrike are exacerbated by the bubbles in the wine. So I guess that means that rosé coloured sparkling wines are the most susceptible wines.
Making the problem worse, those clear glass bottles (pictured right) fail to protect wines from UV light. (Read more on the problems with clear glass in the section below on ‘advancements in technology’.)
How to prevent lightstrike?
Good wine preservation is why cellars are often dark, cold places below ground. It’s not just sunlight that emits damaging UV light, fluorescent lightbulbs and traditional incandescent lightbulbs are often the culprit behind the blue rays of UV light.
That’s why they recommend LED (light emitting diodes) lights for wine cellars as they generally do not emit UV. As an added bonus, LED’s give off a minimal amount of heat.
Of course, even if you are diligent in keeping your wines out of the light, the wines could have been spoiled previously. Researchers have discovered that the bottling line is where some wines may be damaged by light exposure.
More frequently, wines are most often exposed in shops, bars, restaurants and supermarkets. Bright lit supermarket isles and wine display cabinets showcasing wine bottles use light to draw attention to the wines.
How advancements in technology can reduce lightstrike...
By using coloured glass for wine, producers can prevent lightstrike. In fact, clear glass only protects wine from 10% of the harmful light; green glass 50%, and unfashionable amber glass, 90%.
Furthermore, most wine professionals are still unaware of the problem of lightstrike. Therefore, marketing departments will put pressure on producers to bottle wines in clear glass bottles.
Always take special care in evaluating wines that you buy in clear glass bottles!
One study of glass bottles on supermarket shelves, found that
lightstrike occured in some wines in clear bottles after just 1-2 days. But all of them developed the fault after 20-40 days. The green glass offered protection for up to 50 days.
But volatile sulphur components can be formed within 1 hour of exposure.
Then there’s the wine packaging trend called ‘lightweighting‘.
Unfortunately, lightweighting is terrible for preventing lightstrike.
A matter of fashion...
- when buying wines from a display fridge, pick bottles that are placed a few bottles away from the light source. Usually, this means a few rows back as the lights tend to shine on the first row. This way, you’ll lesson the chances that you get a bottle with lightstrike.
Famous Champagnes are taking note...
The wine region leading the way in taking lightstrike seriously is Champagne. Considering the price and reputation of these wines, perhaps this is not surprising.
For many years Cristal, the cuvée prestige (top bottling) from Champagne house Louis Roederer, has taken steps to prevent lightstrike in their wines. For over a century, Cristal has been bottled in a clear glass bottle.
This famous design was created for Tzar Alexander II who wanted to make sure no poison could be put in his wine. Making the glass clear would enable anyone to see if the wine had been tampered with.
Roederer has kept this design but the bottles come with orange cellophane wrapping to protect the wine from lightstrike.
Other luxury Champagne brands have since followed suit.
The famous Champagne house Ruinart recently launched this eco-friendly ‘Second Skin’ for Earth Day in 2021. This lightweight packaging also protects the bottles from harmful UV light that causes lightstrike.
Other Champagne brands sell bottles in individual boxes to protect them from harmful UV light.
Unfortunately, for most wines, fashion overtakes function in bottle presentation. Therefore, if you’re drinking white, rosé or sparkling wines, I’m certain most of you have drunk a wine spoiled by lightstrike.
Lightstrike is one of the most common wine faults out there. Only recently have researchers and producers appreciated this common fault and understood how to protect bottles of wine from getting to consumers faulted. Unfortunately, as this fault happens primarily on store shelves, it’s up to the consumer to know whether a bottle tastes the way it should.