Crop insurance gets new tools for wine smoke taint
The ability of growers to recoup some of their financial losses from grapes took a significant step forward this week as new research came to light on effective testing methods for wine taint, the elusive result when, like recent weeks, fires ravage wine country.
During a California Association of Winegrape Growers webinar on the issue Wednesday, agents from Pan American Insurance Services said the federally directed crop insurance system has previously considered proof of a “smoke taint” claim to be only third-party grape test results that show “elevated” levels of chemical compounds linked to the campfire, medicinal or ashtray characteristics.
But UC Davis enologist Anita Oberholster, Ph.D., one of three key West Coast researchers helping the U.S. wine business assess and deal with the taint issue, presented findings from Australian and U.S. research that suggest small-scale tests for taint in fermented wine made from suspect grapes can be a more accurate predictor of later problems than tests of just the fruit itself.
For example, testing small-scale ferments of grapes from 13 sites during the 2018 Ranch Fire in Lake and Mendocino counties revealed levels of a key chemical marker of taint — free volatile phenol guaiacol — three to five times higher than in tests of only the fruit from those vines, Oberholster said in her presentation. Growers in those two counties had an estimated $37.1 million in fire and smoke damages from that 410,000-acre blaze.
“We’ve not seen it here, but in Australia, where they have a lot of data points, they have seen incidents where the free (volatile phenols) were almost undetectable in the berries and then showed up in the ferment,” she told the Business Journal.
A number of North Coast farmers learned the hard way amid major wildfires in the past several years when their crop-insurance claims were rejected because grapes deemed unsalable weren’t tested before harvest for the key indicators that the resulting wine could develop smoke-related problems, according to Oberholster.
ETS Laboratories, one of the independent testing firms that serves the wine business, had posted on its website earlier this week that turnaround times on smoke test results were delayed because the firm has had to staff up to handle an influx in samples, and testing is limited to the two main taint indicators for the time being. By Thursday, the lab was back to offering test results in one or two days.
Heat from burning vegetation creates volatile phenols that travel in the smoke and, depending on a number of factors that are still being explored, can be absorbed into the vine leaves and grape berries. Of the seven volatile phenols associated with smoked wine, two primary indicators are guaiacol and 4-methylguaiacol.
Problem is, these compounds easily bind with sugars in the grapes, creating six known “bound” compounds, which are converted back to the “free” forms during fermentation. So analyzing the fruit alone can miss the potential problem.
A lot is at stake with the issue. Harvest is barely underway of the North Coast wine grape crop, which was valued at $1.7 billion last year. Knowing which fruit could have issues and which may not can affect decisions on grape purchasing, harvesting and winemaking.
And uncertainty about the impact on given vineyards while smoke from the Hennessey and Walbridge fires in Napa, Lake and Sonoma counties has wafted across multiple states has prompted growers and wineries to flood local testing laboratories with samples.
After the two-hour trade group webinar, officials from the U.S. Department of Agriculture’s Risk Management Agency, which oversees crop insurance, told the Pan American agents that they were convinced a change was needed to the claim-documentation process, and the allowance for fermentation tests would be rippling down to the insurers in the program, according to Oberholster.
“The grower still needs the berry number. But, say, the berry number shows nothing, and they can show elevated (levels) in the microfermentation, (the carriers) will potentially honor that insurance,” she said.
One of the challenges with defining “elevated” in crop policies, “reasonable cause” in California agricultural law or “free from any detectible taints” in some grape purchase contracts is that there are no firmly established baselines for these levels in grape and wine samples.
Detection of under 0.5 micrograms per kilogram (parts per billion) of guaiacol in a grape sample is considered to be a marker of low anticipated risk of smoke taint in the resulting wine, with over 1 part per billion suggesting moderate risk and over 2 parts per billion pointing to “very high” risk, according to ETS. For microferment samples, the grey area of unlikely to possible problems with smoky aromatics is 1–4 parts per billion.