UV-Flavoured Wine
Who cares about the price to be paid for improved quality ...
A good one for the festive season
New Zealand is known for its distinctively flavoursome wines. That flavour may come at a price, but it’s a price worth paying.
One of my colleagues, Rainer Hofmann at Lincoln University, has been working on the issue of UV and wine. If I’d been a bit younger, I might have put up my hand to help with his wine studies. The paybacks might have been worth while. 😊
He also works on the UV effects on clovers, but while that may be of interest to sheep, I must say that the wine angle is much more appealing to me.
I live in Central Otago, in the lower south Island of New Zealand (near latitude 45 S). The region’s famous for its world-class pinot noirs. It produces some very nice white wines as well. But New Zealand’s international reputation for quality wines was built on its white wines, especially the sauvignon blancs produced mainly in the Marlborough region at the top of the south island (near latitude 41.5 S).
The sauvignon blanc variety came to us from the Bordeaux region of France (latitude 45 N), which is significantly further from the equator (by about 4 degrees of latitude), so its noon sun elevation angles are about 4 degrees lower in the sky. As a result, it receives less UV. But the amount of UV received in Bordeaux is much less even than in Central Otago, which the same distance from the equator (both are at latitude 45 degrees). Typically, the peak summertime UV is about 40 percent more at southern mid-latitudes than at corresponding northern latitudes (due to the closer Sun-Earth separation in December/January, lower ozone amounts in the southern hemisphere summer, and cleaner air in the south).
I’ve just checked that 40 percent figure using the Variation Display tool in our updated GlobalUV smartphone app. While at Blenheim (NZ) the clear-sky summer maximum UVI can exceed 12 (n January) , it reaches only 8.5 or so at Bordeaux (in July). The app works!
Anyway, work by Reiner and his colleagues published in 2000 showed that increased UV exposure causes more flavonoids in grapes, (which presumably makes their wines more flavoursome). I see the paper has been cited over 1,100 times, so I’m not the only one interested! It follows that, because of the higher UV levels in New Zealand, the concentrations of these flavonoids are higher in the local version of wines from that grape variety. And that’s why our wines taste better.
All that doesn’t, however, explain why New Zealand whites are better than Aussie whites. Their UV is higher still. Could rainfall, temperature and terroir also be important?
Reiner is one of the few who’ve contributed to all the NIWA UV Workshops that I’ve convened over the last 20 years or so. At those, he’s discussed a couple of possible disadvantages of UV exposure.
First, the productivity of grapes (and clovers, in case any sheep are reading this) may be reduced by exposure to UV, which could increase prices. That’s probably not a problem for wine, because for the highest quality, some grape thinning is needed anyway.
The second concerns shelf-life. During a quiet moment at the most recent UV Workshop, he whispered a secret which you must promise not to repeat. He said that the presence of these flavonoids may also reduce the shelf life of the Kiwi wines (he didn’t mention that in his papers because I think the wine industry may have been one of the funders). But for me - and for most others I suspect - that’s not an issue. They rarely last more than a few years at my place! And not because they’ve gone off. It’s because they’re so good that they’ve already been appreciatively consumed. Cheers!
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