The short answer is that light can definitely affect wine, but we need to take a closer look at the physics and chemistry of it all to understand why and how in what is called light stroke reactionsthat can impart bad odors to the wine, what the French call taste of light.
Wine is sensitive to harmful light rays, particularly ultraviolet (UV) rays from sunlight and fluorescent lighting; that’s why wine (and beer) are packaged in dark bottles; the best example is Port in those familiar, dark, opaque bottles. Wines packed in clear glass bottles are intended for quick consumption and should be stored in cardboard boxes until then.
All forms of radiation, including visible light ultraviolet (UV) rays and X-rays, have energy that is directly proportional to their frequencies or inversely proportional to their wavelengths, that is, high-frequency waves have lengths shortwave and vice versa. And the higher the energy, the greater the catalytic effect of chemical reactions in the wine.
In wine, visible light and UVA rays from the sun, yes, UVA rays, are a cause for concern because research has shown that even brief exposure of wine to the sun (UVB and UVC rays are absorbed by the atmosphere), from order of hours, can have detrimental effects. This is because UVA rays are in the 315 to 400 nanometer (nm) range of the electromagnetic spectrum and therefore have more energy than visible light, which is in the 400 to 700 nm range. .
Glass acts as a filter, but clear glass offers no protection against UVA rays and visible light. Green glass offers some protection, but only half as good as amber; Dark amber glass offers almost complete protection. So why is so much wine, particularly many of the world’s ultra-premium wines, packaged in green glass? This is likely for historical reasons when making green colored glass was easier and the effect of radiation on wine was unknown.
But the glass is only half the story. We must now consider the optical properties of wine in order to later determine how radiation affects any chemical reaction.
Research has shown that wavelengths in the 375-440 nm range, i.e. the high end of the UVA range and the blue (low) end of the visible light range, are the most damaging to wine. The amount of radiation absorbed by the wine in this range is directly proportional to the opacity; therefore, red wine absorbs the most and is the most affected, while white wine absorbs the least, rosé wine is in the middle. As such, for marketing purposes where display of color is important, white wine may be stored in clear glass, although not for extended periods of time; That’s why premium white wines, like age-worthy Chablis wines, come in dead-leaf glasses, a golden-yellow color that provides better protection than green.
Rich, opaque, deep-colored reds absorb most of the radiation; however, these have the highest concentration of effect-inhibiting tannins, which provide protection. But if the concentration is low or the degree of exposure is prolonged, unpleasant and repulsive aromas and flavors may develop. Specifically, red wine has sulfur-containing amino acids, that is, they contain methionine and cysteine, which have a thiol (sulfur-hydrogen) side chain in their structures. These then react with naturally occurring vitamins, such as riboflavin (vitamin B2) and pantothenic acid (vitamin B5), water-soluble vitamins that are easily destroyed by heat, oxygen, and, of course, ultraviolet light. The products of this reaction are sulfur compounds such as hydrogen sulfide, dimethyl sulfide (DMS), and dimethyl disulfide (DMDS), responsible for imparting a variety of foul odors, from rotten eggs to cabbage to wet dog.
interesting science.
And now I wonder if my prized 1991 Château d’Yquem magnum, in a clear glass bottle, which I bought for my son born that same year, was X-rayed on its way from the US. It was pre-9/11 September, however, the ruthless airport security guard simply couldn’t be talked out of taking an X-ray of my prized bottle. I guess he was not a fan of fine wines.