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California researchers say there’s a better way to detect wine ‘smoke taint’ from wildfires

New research claims to give wine grape growers, wineries and insurance companies a better way to figure out whether wildfire smoke has damaged the crop on the vine, a concern that led to much fruit in Napa and Sonoma counties to go unpicked in 2020.

But a key West Coast scientist in this field, while noting the advancements in the process of detecting “smoke taint” in the study, urges caution with promoting it as the best solution, given current lab capacity and crop insurance policies.

Determination of smoke damage is critical because it can factor into payment of crop insurance claims.

A team of California Central Coast scientists and laboratory analysts with North Coast agricultural advisers studied 218 wine and fruit samples for eight major grape varieties from 21 appellations in California and Oregon, including the North Coast, from the 2017 through 2021 vintages.

Researchers at SC Laboratories analyzed the samples looking for signs of six chemical markers most associated with “ashy,” “bitter” and “smoky” odors and flavors colloquially called “smoke taint.”

They advocate for direct measurement of those biomarkers, rather than the indirect measurement common now. They say it’s a faster way to know how much of a problem, if at all, they will become as the wine is produced and before it reaches the bottle.

The research also puts forward baseline — pre-wildfire — levels for these compounds across grape varieties by analyzing samples deemed affected and not affected by smoke.

The study was published March 3 in the Journal of Natural Products, an open-access publication of the American Chemical Society and the American Society of Pharmacognsy.

Led by UC Santa Cruz oceanic biochemist and small-scale vintner Phil Crews, the research focused on one of the biggest problems with detection of current and future problems from these smoke compounds in grapes and wine. The issue came to the forefront after a string of Northern California wildfires starting in 2015.

Burning vegetation produces over 500 such volatile phenols. Nearly three dozen are associated with smoky odor and flavor, but a number of those also are connected with desired character given to wine via toasted barrels, the researchers wrote.

The groups’ paper noted how easily and quickly volatile phenols pass through the grape skin to become chemically “bound” to sugars in the berry. At that point, they become odorless. Only during fermentation or contact with enzymes in a taster’s mouth are the volatile phenols released, called “free” compounds.

“Supertasters,” or people with a greater density of taste buds, can detect more of these free volatile phenols, and up to one-quarter of people are physiologically incapable of detecting them, the report said.

“Most labs do indirect measurements of the molecules,” Crews told the North Bay Business Journal. “We did direct measurement of the compounds.”

Crews admits the direct measurement of the bound compounds runs counter to what’s advocated by West Coast smoke-taint researchers such as Anita Oberholster of UC Davis. For the past few years, she has been recommending that growers and wineries conduct “bucket ferments,” also called microfermentations, of suspect grapes to give labs a sample of what the level of free volatile phenols the grapes contain.

“He's very much focused on, ‘This is the only kind of analysis you would do,” Oberholster said. “And I'm always careful saying that kind of thing, basically because I'm thinking of all the other aspects.”

Jeff Quackenbush covers wine, construction and real estate. Reach him at jquackenbush@busjrnl.com or 707-521-4256.

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