Light strike can dull all those bright fruit flavours in your wine and, at worst, introduce a series of unpleasant smells, such as rotten cabbage or eggs, as well as ‘wet wool’.
Broadly speaking, it can occur if UV rays or ‘blue’ light from the sun or artificial lamps – such as fluorescent tube lighting – react with components of the wine, creating off-smelling sulphur compounds.
Studies have shown that green glass bottles offer greater protection than clear glass packaging, although amber glass is an even greater safeguard against potential problems.
Recent research published in the Food Packaging and Shelf Life journal found that green glass could protect some white wines for up to 50 days.
Some wines are generally more susceptible than others. Most at-risk generally include white wines, particularly more delicate styles, plus sparkling wines and rosé wines, according to Dr. Akshay Baboo, programme manager for wine production at Plumpton College, a centre for wine education and training in the UK.
There is debate about the proportion of wines affected by light strike, also known as Goût de Lumière in French.
While some trade professionals and wine lovers may be alert to the issue, Dr Greg Dunn, head of Plumpton College’s wine division, said as part of a recent awareness campaign that ‘many in the broader wine trade and general public remain oblivious to this problem’.
At Plumpton, ‘light strike has been on the syllabus for many years and a number of research projects have been conducted’, Dunn said.
More on the causes
A link between light strike ‘flavours’ and off-smelling sulphur compounds was demonstrated in a study in 1983 (Maujean & Seguin), according to a technical note by the Australian Wine Research Institute.
More specifically, it is understood that light reacts with riboflavin in the wine and that this can result in sulphur-containing amino acids becoming oxidised, which may in-turn lead to the development of sulphur compounds.
It is light at relatively short wavelengths, such as UV, that poses the biggest potential problem.
A report in 2008 by the UK’s Waste & Resources Action Programme (WRAP) said artificial lighting could be ‘the principal mode of exposure’ for many wines, although it also noted a lack of complaints from consumers about spoilage.
Wines most at risk
Plumpton’s Dr. Baboo said that any winemaking or ageing method that creates a reductive environment potentially also generates a ‘stellar breeding ground for this issue’; albeit reductive techniques have advantages, too, not least the preservation of primary fruit aromas.
But, he added that the risk is never exactly the same because ‘every wine is different’.
Previous research has found that tannins in red wine can help to block light strike reactions.
Cutting the risks
While Baboo said that light strike prevention was a talking point within the trade itself, there are also ways for wine lovers themselves to minimise the risks.
‘Keep wines away from direct light,’ he said. ‘Store your wine in the coolest, darkest part of your house.’
At a picnic, keep the wine away from direct sun or consider sitting in the shade. It shouldn’t be too much of a problem, ‘as long as you’re sitting in a cool place’, he said.