Rathfinny Wine Estate

Light Strike

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Some years ago when studying wine making at Plumpton College I read about Light Strike. It’s a wine fault that’s been known about for some time and it’s the reason why we chose to bottle our wine in dark, antique green coloured bottles.  Now we hear that a certain supermarket is planning to do something about it and will soon stop stocking wine in clear glass bottles. So is light ruining wines?

There are several common wine faults, the most talked about is cork spoilage. This affects about one bottle in every two cases, and is caused by a fungus in the cork that gives a taint to the wine (2, 4, 6, Trichloroanisole TCA). It makes it smell like wet cardboard or newspaper, or is often described as a wet dog or grandma’s basement type smell! Got it? It was the reason why many Australian winemakers gave up on cork years ago and switched to screw caps. Other common wine faults include oxidation from too much exposure to oxygen and heat damage. This can cause a protein haze and other problems. It happens when wines, being shipped around the world, pass through places like the Red Sea where temperatures inside shipping containers can get up to 60-700C.

Light Stike is caused by wine being exposed to sunlight and/or fluorescent light when on display in a shop window or on the shelf. The UV or blue light transforms the amino acids in wine into compounds (dimethtyl disulphide DMDS) that smell like a wet sweater, damp cardboard or old cabbage. It’s the reason why Louis Roederer’s Cristal, bottled in a clear glass, comes with an orange cellophane wrapper, and why most Champagne is bottled in dark glass bottles. It particularly affects more delicate wines like sparkling and rosé wines and the bubbles, in sparkling wine, exaggerate the fault. Wines exposed to light for relatively short periods of time, even as short as half an hour, can be affected so we need to protect against it.

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To get a bit technical – visible light has a wavelength of between 400 to 700 nanometers whilst we’re talking about UV or near UV light with a wavelength of 200-420 nm.  The following link gives more information if you want to read more, but we’ve done various things around the Winery to ward off light strike; all our lights are special non-UV emitting lights and we bottle in dark antique green bottles that block about 90% of harmful UV light whereas lighter green bottles only block about 50% of such light.

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So when you’re next reaching for a bottle of rosé, or a more delicate white wine like a Pinot Gris or Blanc, look for one in a darker green or amber coloured bottle just to be on the safe side.

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Isn’t it a little bizarre that beer, which also suffers from this sort of photochemical deterioration is normally bottled in amber coloured glass but wine makers still insist on using clear glass bottles?

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  • That’s very interesting and something that I’d never heard of. I will now see who else is similarly ignorant and will charmingly patronise them! Thank you, Mark.

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