Tuesday, November 9, 2010

When Demystifying Terroir Turns into Bad Science

Wine Peeps, a Washington-centric wine blog, posted, at first glance, a compelling article documenting formal chemical analysis of a Syrah from the producer Cayuse. This is essentially a "cult wine" producer who critics have consistently lauded. The gist of the article is that the wine showed some seriously funky characteristics consistent with high levels of mercaptans or volatile sulfides. So the authors paid to have a sample of the wine tested by ETS in Napa to determine if the compounds were present in abnormally high concentrations. The results were compelling:
Within two days, we had the results, posted online and emailed to us. Then we had a follow-up call with a representative at ETS to discuss the results. The evidence was clear. The Cayuse was a flawed wine. It had volatile acidity slightly above the normal sensory threshold but at a level a massive Syrah can support, but the worst result from the chemistry panel was that it had a high pH level, which made it more susceptible to bacterial attack. The most damning result, however, came from the sulfides panel. Published literature and ETS studies say that low levels of dimethyl sulfide can contribute roundness, fruitiness, or complexity; however, at levels greater than 50 ug/L, it may contribute vegetative, cooked cabbage, or sulfide smells to wines. According to the ETS representative, this wine had the highest dimethyl sulfide level he had ever seen (312 ug/L), more than 10 times the normal sensory threshold (17-25 ug/L), which accounts for the canned corn, rotten vegetables, and decomposed greens flavors. And, those dimethyl sulfide levels and resulting unpleasant sensory characteristics will only increase with wine age, according to ETS.
What was apparently attributed to terroir is apparently an extremely high level of dimethyl sulfide. (Just as a cross-reference, Jamie Goode confirms that various sulfides can bring some serious funk.) Perhaps the terroir does indirectly contribute to this character by producing fruit that naturally ferments in a manner that generates high quantities of volatile sulfides. Or perhaps it's mostly the "house style" that shows, especially if fermentation technique is reductive. Maybe a high pH allowed some in-bottle microbial development. In any case, though, it's clear those attributing the sulfide-heavy character directly to terroir are not on firm footing. Many factors can contribute to production of sulfides.

The Wine Peeps, however, go awry arguing that this is some sort of objective, absolute and unequivocal flaw, especially in the comments that follow. I love science more than most people, and data indicating the presence of stinky compounds is priceless in my book. But when it comes to personal taste, objectivity simply doesn't exist. The most one can do is indicate that sulfides have a large sensory impact.

I recently wrote about a Merlot that had an intense briny, seaweed characteristic, which may well be related to volatile sulfides. In any case, it is quite likely some less than commercially acceptable sulfur-based compound was present in a high concentration. Yet I really liked this "flawed" wine. The seaweed aroma made it unique and interesting. For a mass market wine this would not be desirable because it may well displease a large segment of consumers. But for smaller production wines the real art is in differentiation if not a tension between easy to like flavors and more challenging ones.

Ultimately it comes down to taste. One man's flaw is another man's intriguing characteristic. Some folks like fruity, oaky wines. Others like stinky, dirty wines. Who's right? Is excessive fruit a flaw? What about high alcohol? No, it's about taste. Many technically "flawless" grocery store wines I try have a vanilla if not tapioca or yogurt flavor most likely due to spoofy oak treatment. This is way above my sensory threshold. But is it a flaw? No. I just don't like this flavor. Others do, and that's fine.

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