white wine bottles in wine shop

“Wine is complicated. Almost impossibly so.”

Jamie Goode from his book, Flawless: Understanding Wine Faults

Unless you’re a winemaker or chemist, there’s a lot we take for granted about wine. At the very least, you can buy a random bottle off the shelf and odds are it will be decently well-made and stable. Not so once upon a time. Winemaking is better today than it’s ever been on a global scale. Still, wine chemistry is remarkably complex and wine quality can be altered even after the juice is in the bottle. Exhibit A is oxygen-transfer issues with different types of closures. Then there’s the packaging itself, which can also lead to quality variability. That holds especially true for the kind of glass used in the production of bottles.

Recently, Susie Barrie and Peter Richards, both Masters of Wines—and a married couple, were interviewed on the BBC One Saturday Kitchen program. The two decried the use of clear glass bottles for packaging wine, saying that light interacting with wine in transparent bottles can develop a host of problems including smelling of “boiled cabbage and sewer.”

The problem is called light strike. The French term is la goût de la lumière, literally, the taste of light. It sounds poetic, but in reference to wine, it’s anything but. Bottling wine in clear glass is problematic at best. The interaction of UV rays from sunlight or blue light from artificial sources with wine produces volatile sulfur compounds such as dimethyl disulfide. DMS, as it’s often called, smells, and tastes like Barrie’s and Richards’ cabbage and sewer. I’d add rank cauliflower and broccoli to the mix.

For the more technically-minded, light strike happens when light reacts with riboflavin in a wine and photo-oxidizes methione, a sulfur-containing amino acid. The result is foul smelling thiols and thiol esters as well as the previously mentioned DMS. A secondary reaction between light and the tartaric acid in wine also forms glyoxylic acid and hydrogen peroxide that can cause the color of a white wine to turn yellow or brown.

Susie Barrie went onto say that light strike is a major issue for wine consumers. “The scope of the problem is probably much larger than any other odor in wine, yet we don’t talk about it. Generally, we accept it, sometimes unintentionally embrace it, but mostly continue to pretend it’s not a problem, while, in fact, it robs us all of our rightful enjoyment. It’s daylight robbery in every sense.”

Barrie and Richards also pointed out that clear glass bottles are especially problematic for sparkling, white, and rosé wines. In particular, how even limited exposure to light on a retail shelf with wine bottled in clear glass quickly alters the aromas and flavors. Mind you the light issue rarely impacts red wines because they are protected by polyphenol compounds and tannins.

Using green or amber-colored bottles goes a long way to prevent wines from developing light strike problems. To that point, a recent article in the Food Packaging and Shelf Life journal (yes, there is such a thing) stated that green glass could protect certain white wines from light for up to 50 days.

Several thoughts come to mind. First, clear glass bottles are widely used for lighter white wines such as Pinot Grigio and Sauvignon Blanc, as well as rosés and other blush wines. Transparent glass is less frequently used for sparkling wines, although some domestic blanc de blancs are often found in clear bottles. With the exception of the latter, most of the wines done in clear glass are intended for near-term consumption–within a year of release. So any concern on the part of the winery is probably minimal, given the wine’s intended lifespan. However, once released into the market, there is no control over how a wine will be displayed at the point of purchase—as in direct sunlight, or how long a bottle will sit on a retail shelf.

Light strike can still occur in restaurant settings given how poorly wine is often stored. Then exposure to light may not be the only problem. I remember ordering a bottle of Barbera from a favorite producer one time in a restaurant in San Francisco, only to see the bartender grab the bottle from a row of wines next to the espresso machine. When opened at the table, the wine was the temperature of a warm bath. An ice bucket was quickly procured.

I should also point out that light strike is a problem with beer packaged in clear bottles (Corona and Pacifico to name two), as well as olive oil. If you think about it, prolonged exposure to any form of light for beverages or food stuffs can’t be good. The exception being diet soft drinks, some of which seem like they’re two molecules away from plastic.

Ultimately, caveat emptor is the bottom line when buying wine at retail. I live in Rio Rancho, New Mexico, a secondary market if there ever was one. I’m mindful to always check the vintage on any wine I’m considering purchasing. If anything, because the temperature throughout the year in any retail venue can considerably vary. Thus any bottle that sits on the retail shelf for an extended period of time has experienced repeated temperature fluctuation. There’s also the lack of humidity here which is typically between 5-15%. So any wine that’s been on the shelf for several years could potentially have a dry faulty cork. All of which means I never take the first bottle of a wine on a shelf—or the top bottle on a stack. Instead, I always reach for a bottle behind or underneath, not exposed to so much light.

Should wineries address the light strike issue and phase out clear bottles, using green and amber glass across the board? It’s an easy fix and would go a long way in avoiding light strike issues. Surely cost can’t be that much of a concern. If so, it’s probably minimal and any increase could be factored into the price of the wine. However, I don’t see change in the offing any time soon. Unless consumer complaints reach a certain threshold, large wineries and conglomerates won’t be changing packaging any time soon. That is, unless a “scandal” of sorts erupts in the media, like the one for sulfites, MSG, or similar.

In the end, light strike will continue to be an issue for wines bottled in clear glass. So best to be mindful when reaching for that bottle of Pinot Grigio or so-called organic olive oil at the supermarket. And make “reach behind or reach below” your mantra. You’ll be glad you did.