'Smoke taint' worries rile Northern California growers as wine grapes rejected after summer wildfires

Research on smoke taint in wine

Major Lake County wine grape grower and vintner Clay Shannon plans to crush about 6,000 tons of grapes this year, enough to make about 360,000 standard 12-bottle cases of wine.

But as much as one-third of that haul he is taking on is because the original buyers reportedly told him the grapes would be tainted by smoke from record-sized wildfires in Lake and Mendocino counties this summer.

After the massive North Bay wildfires during harvest in October last year, record-sized blazes this summer in Mendocino and Lake, and big burns in Oregon and British Columbia, concerns about 'smoke taint' in wine have wafted up from Down Under to become a hot North American industry issue.

'The talk is starting to affect me and irritate me,' Shannon said.

The 2,200 tons of grapes he's buying that had been deemed suspect by some large-scale producers are coming from vineyards in which he has some ownership stake and others in which he doesn't. Shannon said a distributor recently quizzed him on the potential for smoke taint from recent fires.

The Lake County Wine Commission, a grower marketing organization for growers, recently announced a research partnership with ETS Laboratories, which has a Napa facility, on smoke taint to help clear the air about the issue.

Working from testing protocols developed over the past decade and a half in Australia, ETS and other wine labs in the Western U.S. have been processing hundreds of samples of grapes and fermented wine from growers that want to know what's salable and vintners eager to know what they may be working with.

Australian research on the interplay between smoke in the air and potentially unpleasant 'ashtray' smells and flavors in the bottle has increased the number of culprit compounds to test for to seven, up from two. But how tests on grapes and wine will predict 'smoke taint' and how winery can fix issues remain to be solved, according to local analysts.

A big challenge in such testing is the chemical markers associated with the off odors and flavors travel come in two forms: nonvolatile precursors and volatile compounds consumers can detect. The nonvolatiles bond to sugars in the grape juice and get released gradually during fermentation into the volatile, or free, form.

Commercial labs have precision in detecting levels of the nonvolatile and volatile chemicals, but the meaning of those levels in predicting taint isn't well-known. Some varieties of grapes, especially syrah, have naturally high levels of precursor compounds, and wine contact with toasted oak in barrels and tanks will skew results.

But a big factor is there is no real baseline for taint compounds by appellation in the U.S., compared with multiple years of no-fires test results compiled in Australia, according to José Santos, president of wine chemistry testing and supplier Enartis, which has a Windsor location for its Vinquiry Laboratories division.

That said, the smokiness in North Coast air this year was quite different overall from that of a year ago and from fires in the Pacific Northwest, and that is reflected in test results. Rather than laying low like a throat-choking fog, the plumes during the Mendocino Complex fires this year tended to rise higher and blow away.

'The highest numbers we found this year are significantly below what was found last year in Napa and Sonoma,' Santos said. 'The majority were probably below the lowest numbers we found last year. We don't see that there is a major issue with the smoke this year in most cases, because the levels are specifically low. If the fruit and resulting wine are managed accordingly, most potential issues can be addressed.'

But there have been vineyards with problems. Shannon noted that grass was burning between the rows of 30 acres of pinot noir vines and five of pinot gris in his Long Valley ranch property, and they those grapes do have taint issues. Frey Vineyards in Mendocino County's Redwood Valley had to reject 30 tons of sauvignon blanc and 40 tons of cabernet sauvignon from the Upper Lake and Elk Mountain areas of Lake County because the test results from the grapes, grown in vineyards that were next to the fires, were 'very high,' according to Katrina Frey.

That said, Shannon plans to work with the Long Valley wine this year to try to make great wine, similar to what his company did in making 1,400 cases from barbera grapes tainted during the 2008 blazes. He linked it to not rejecting a child or partner who wasn't perfect.

Because researchers at the Australian Wine Research Institute and University of Adelaide are several years ahead in smoke-taint benchmarking, Vinquiry Laboratories has worked out a system for sending batches of wine samples for more detailed testing by the institute. Details are in flux, but the plan is to get results within a week to 10 days. The first samples go out this month, he said.

Research on smoke taint in wine

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