Have you ever tasted wine that smells and tastes like “cooked cabbage and wet dog”? If so, you might have attributed the spoilage to heat or cork taint, which are both uppermost in our minds when we think of spoiled wine. But research asserts that light presents a bigger problem, particularly for white wine. When white wine, especially in a clear glass bottle, is exposed to ultra violet and visible light at the blue end of the spectrum, it can spoil within a few hours, a condition known as light-strike, which initiates chemical reactions that produce moldy aromas and flavors. The most likely culprit for this condition is fluorescent lighting in markets and wine shops.
Introduced by long-time wine club member John Juergens, Ph.D. in Pharamacology, this research was a big surprise for me. I rarely buy wine at stores and have never tasted a spoiled white wine that I can remember. Most of the wine that I taste or consume is extracted from the corrugated box, into which the winery has placed it. At a tasting in my office or at a formal tasting venue, the wine emerges from the box or a bottle carrier that a sales person might be using and is poured directly into glasses. The wine I sample at wineries is equally protected. And any wine that you receive from Celebrations Wine Club also quickly emerges from the case and is repackaged for club members, exposed to light for only several minutes. Normally, neither do restaurants and bars store wine around bright light. But if you buy wine from stores, beware of light-strike.
“To reduce waste and recycle more,” the Waste & Resoures Action Programme in the U.K., which is promoting the use of lighter-weight wine bottles among other measures, has done a series of studies to better advise the wine industry. According to one of its studies, light-strike is a problem and one that most wine producers are aware of. Apparently, red wine is rarely subjected to light-strike, because the tannins in red wine protect against the condition. On the other hand, white wine and rose` contain only slight amounts of tannin and are by far more vulnerable.
The color of the glass bottle is extremely important, according to the study. Brown is the most protective and blocks the ultra violet and blue range of light by as much as 90 percent. Possibly wine producers have deliberately avoided brown glass to distinguish themselves from beer producers, who bottle almost exclusively in brown glass. Green glass blocks just 50 percent of light and white glass only 10 percent. Thicker glass, even when clear, blocks more UV light than thinner glass, and bottles with less pronounced shoulders reflect more light.
Because clear glass is more valuable in terms of recycling, the Waste & Resources Action Programme is suggesting that glass producers add certain chemicals to clear bottles to block UV light. The agency is also advocating sleeves and coatings for bottles. But at this point, these measures would increase bottle costs and are unlikely to be adopted.
So regarding light-strike, the take-away is to avoid clear or green bottles of white wine on tops shelves that would be most exposed to light sources. You might also reach for the bottle in back of the first one on a shelf. And of course, avoid light contamination at home. Just when we think we know enough, oops…. There’s more.