California researchers promote a better way to detect the smell of wine smoke caused by wildfires

New research claims to give grape growers, wineries and insurance companies a better way to determine if smoke from wildfires has damaged the crop on the vine, a concern that has led to many fruits in the Napa and Sonoma counties will not be picked in 2020.

But a key West Coast scientist in this field, while noting the progress made in the process of detecting the “smell of smoke” in the study, urges caution in promoting it as the best solution, given current laboratory capacity and crop insurance policies. Determining smoke damage is critical as it can be factored into the payment of crop insurance claims.

A journal article written by a team of Central Coast California scientists and lab 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 vintages 2017 to 2021.

Researchers at SC Laboratories analyzed the samples for signs of six chemical markers most associated with “ashy”, “bitter” and “smoky” odors and flavors, colloquially referred to as “smoky taste”.

The article advocates the direct measurement of these biomarkers, rather than the currently common indirect measurement, as a quicker way to know how much of a problem they will become, if at all, as wine is produced and before he reaches the bottle. The research also proposes baseline levels – before forest fires – for these compounds in grape varieties by analyzing samples found to be affected and unaffected by smoke.

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

Led by UC Santa Cruz ocean biochemist and small winemaker Phil Crews, the research focused on one of the biggest problems in detecting current and future problems with these smoke compounds in grapes and wine. . The problem came to the fore after a series of wildfires in northern California starting in 2015.

Burning vegetation produces more than 500 of these volatile phenols. Nearly three dozen are associated with a smoky smell and flavor, but a number of these are also related to the desired character given to wine via toasted barrels, the researchers wrote.

The article noted how easily and quickly volatile phenols pass through grape skins to chemically “bind” to sugars in the berry. At this point, they become odorless. It is only during fermentation or contact with enzymes in the taster’s mouth that volatile phenols are released, known as “free” compounds. “Supertasters,” or people with a higher density of taste buds, can detect more of these free volatile phenols, and up to a quarter of people are physiologically unable to detect them, according to the report.

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

The teams worked with SC Laboratories, which was interested in studying smoke for its applications to the cannabis industry, to set up equipment and processes to become one of only three laboratories in the world to use this direct analysis to detect these bound volatile phenols in grapes. and wine. The other two are St. Helena-based ETS Laboratories, which has four labs along the west coast, and the Australia Wine Research Institute, which pioneered research into wine smoke damage. for more than two decades.

Crews admits that measuring bound compounds directly runs counter to what West Coast smoke odor researchers, such as Anita Oberholster of UC Davis, advocate. In recent years, she has recommended that grape growers and wineries perform “bucket fermentations,” also known as micro-fermentations, of suspect grapes to give labs a sample of the level of free volatile phenols in the grapes.

“He’s very focused on, ‘That’s the only kind of analysis you would do,’ Oberholster told the Business Journal. aspects.”

One of the main reasons for caution is that the adjustment of crop insurance claims is based on the analysis of free volatile phenols. But she agrees with Crews that measuring bound compounds is the most important indicator of what will happen during wine fermentation. And she’s incorporating some of the new findings on compound base levels into her ongoing research into developing metrics that can be used in grape contracts and insurance policies.

Laboratory capacity is another reason why Oberholster is reserved to focus on the measurement of bound compounds. She noted that the method used by Crews and the research team to speed up the measurements, a maceration of grape clusters for two to four days in a container kept at 60 degrees, is unlikely to be practical in an environment where labs want to deliver results within 48 hours.

“I don’t care if there’s another lab that does this analysis,” she said. “I can tell you now, if we have an event like 2020, in two weeks the labs we have are going to be flooded. It’s not the labs fault. They can’t have the capacity and very expensive technicians and equipment in the event of a disaster. That’s not how you run a business.

Jeff Quackenbush covers wine, construction and real estate. Before joining the Business Journal in 1999, he wrote for Bay City News Service in San Francisco. Contact him at [email protected] or 707-521-4256.

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