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Dan Berger On Wine: Lightstruck — The problem with clear wine bottles

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Should the marketing of a wine jeopardize its quality? If so, something is upside-down.

I refer here to the recent popularity of clear glass wine bottles for many white and rosé wines. Clear glass bottles, called in the industry “flint,” are a clever marketing tactic, allowing us all to see the lovely golden color of white wines.

Many now have silk-screened labels and are works of art.

The problem, however, is that from a wine quality point of view, flint bottles can be problematic. Although the problem isn’t very widespread, it can be hard to deal with since problems arise after the wine has been shipped to market.

At that stage, poor handling can ruin it. It’s one reason so few European white wines show up here in clear bottles. But U.S.-based wine companies love to display the color of their whites and rosés – and now many rosés from the south of France are showing up here in flint glass.

In a nutshell, the problem is light.

The simple act of incandescent, fluorescent, or sunlight splaying on bottles of white or pink wines in flint bottles can ruin the wine. Some will smell a bit skunky. Kindlier, they smell like shallots or onions.

Despite the best efforts of wine and beer producers to protect their products from spoilage, some producers still bottle their liquids in clear glass bottles that have no protectants to ward off problems with ultraviolet light. When hit with as little as a few minutes of direct light, a wine can undergo a photochemical reaction that can turn it smelly.

This cannot occur with beverages in cans or cardboard boxes, which, for this purpose, is a better container.

The so-called lightstruck aroma is far less well-known than corked wine. Most cases of cork taint have been solved by advances in closures. But lightstruck issues seem to pop up in the strangest of places. Once in a Beverly Hills café, I returned such a bottle. Oddly enough, some top wineries are unaware of this problem. One illustration should suffice.

About 20 years ago, a prestigious Napa Valley winery staged a luncheon on a patio. To start, guests would sip the winery’s Sauvignon Blanc – so the catering company pulled corks and put the bottles on sun-bathed tables well before the guests arrived.

I arrived early and was handed a glass. It was spoiled. I told an owner, who admitted that the bottle was “off,” and further admitted that he had no clue that sunlight could negatively affect his flint-bottled SB.

What’s strange about this story is that the same producer continued to use that same flint bottle for its Sauvignon Blanc – and so do lots of other wineries.

Flint is especially questionable for wines that are typically served chilled on patios, where sunlight is hard to avoid. And where it can play havoc with some expensive wines.

I first learned about lightstruck issues in the 1990s while attending a brewing seminar at the Center for Brewing Studies in Sonoma, Calif. The president of the center, the late brew-master Dr. Joe Owades, poured a number of commercial beers for attendees. One was badly spoiled with the skunky smell of hydrogen sulfide.

Owades had bought this particular Dutch brew, in pale green glass bottles, from an illuminated refrigerator case at a local market. He did so, aware it would be a classic object lesson.

“Any form of light combined with a clear bottle creates a photochemical degradation and gives you this smell,” said Owades, explaining that in beer it is the riboflavin that is the catalyst.

He said dark beers or those bottled in brown bottles are less likely to have this skunky smell when exposed to light. He said that just 15 minutes of exposure to light, even sunlight, can ruin a bottle of a delicate beer. Lagers are frequently affected; such brews can smell sort of cat-boxy.

A few high-end French Champagnes that come in clear glass bottles are sold here. Buying one out of a refrigerator case could be risky.

One of the finest Champagnes is Roederer’s incomparable Cristal, which was originally made for Russian Tsar Alexander II, who ordered it bottled in clear glass. Even though wine typically has a lot less riboflavin than beer, Cristal’s owners knew the risks of clear glass. To protect the wine, the company wraps each in colored cellophane to filter out almost all ultraviolet light.

Bottles of Cristal usually are accompanied by a leaflet suggesting that buyers keep the cellophane on until it’s time to open the wine. Of course, this doesn’t mean retailers will keep the cellophane on. Cristal bottles look stylish without it.

After attending Owades’ brewing course, I tested the lightstruck effect with two identical bottles of Chardonnay, both purchased at a local shop. The wines had been bottled in clear glass, and were bought from a shop that opened a sealed case to sell me two.

One bottle was immediately placed in a bag. The other bottle was placed in my kitchen window in direct sunlight, adjacent to an air-conditioning duct. Later both bottles were chilled to the same temperature.

The following day I opened both. The wine that had been exposed to sunlight in the window had a noticeably funky aroma. The bottle from the bag and box was fresh. It had no “off” odors.

Because of their pigmentation, red wines are generally not affected by light. Nor are most wines in dark-colored bottles. That’s why some winemakers use black glass bottles — which have a UV protectant.

Lightstruck issues in flint bottles remain a small problem for the industry, and in fact, some glassmakers now offer flint bottles that are treated to block UV light.

Still, I would avoid buying white wines from stores that display bottles in intense light.

Wine of the Week

2018 Mettler Family Albariño, Lodi ($20)

This attractive floral white wine was made from a grape variety popular in western Portugal and Spain. Its aroma is delicately floral with nuances of tangerine, nectarine, and pineapple, and although it has a soft entry, the finish is dry. The screw-capped, silk-screened bottle is clear, so keep it out of direct sun.

Watch now: Vines on Las Amigas Road before harvest

Dan Berger lives in Sonoma County, where he publishes “Vintage Experiences,” a subscription-only wine newsletter. Write to him at He is also co-host of California Wine Country with Steve Jaxon on KSRO Radio, 1350 AM.

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