How much wildfire smoke can California wine grapes sustain? A new bill aims to find answers.

For five of the past six years, heavy smoke from nearby wildfires has engulfed vineyards full of grapes that Ashley Egelhoff depends on to produce her wine.

While some wine drinkers may enjoy a little smokiness in their Zinfandel, too much can render a bottle kaput. When grapes are exposed to wildfire smoke, they soak it up like a sponge. That creates a condition known as smoke taint, which can make a glass of wine taste like it's been burnt — or worse, served directly from an ashtray, according to vintners and researchers.

Egelhoff, the winemaker at Honig Vineyard & Winery in Rutherford, has been forced to forfeit entire vintages and sell wine in bulk rather than bottle it, curtailing the company's overall inventory and earnings. To limit the fallout, Egelhoff is using her own process to gauge the smoke exposure in her grapes.

Egelhoff's team ferments a small sample of grapes in a mason jar for three days and then performs a taste test. Depending on the level of smokiness, they'll decide whether or not the grapes are too damaged to meet the brand's standards.

"It gives us as winemakers a comfort level, but the problem is that we don't have a common language to communicate that to a grower and you can run into issues with insurance and contracts," she said. "What we really need is a better screening method that allows everyone to be in agreement."

As catastrophic wildfires become a norm across an extremely parched Golden State, vintners seek answers to help the California's famed grape and wine industry endure the effects of climate change. Specifically, they're asking the state to invest in research to answer some of the industry's most pressing questions, including how to know which grapes have suffered damage, what level of harmful compounds can the grapes sustain before they become tainted, and whether there are any ways to prevent smoke taint ahead of a wildfire.

"The industry is in urgent need of these answers," said Noelle Cremers, director of environmental and regulatory affairs for the Wine Institute. "Helping maintain the viability of the industry and not having these significant losses from wildfires is important for the state."

Assemblymember Cecilia Aguiar-Curry, D-Winters, is hoping to help California vintners gain that clarity.

Aguiar-Curry has introduced Assembly Bill 54, which would require the state's Department of Food and Agriculture to fund research on smoke taint in wine, including methods to alleviate and prevent damage to grapes and finished wine. The bill requests that the Legislature set aside $5 million in the budget to create a new funding source for this research.

The bill marks Aguiar-Curry's second attempt at such legislation. Last year, her proposal died in the Assembly Appropriations Committee.

"We're seeing those losses repeated with every new destructive wildfire," Aguiar-Curry said. "Our grape growers need to know how to prepare and mitigate. If we have more data tools and research, it helps us get in front of the problem."

Research examines wildfire smoke impact on wine grapes

Some of this research is already taking place.

In 2021, a coalition of researchers at Oregon State University, Washington State University and UC Davis received a four-year, $7.65 million grant from the U.S. Department of Agriculture to study the impact of smoke exposure on grapes.

Anita Oberholster, one of the lead researchers, is training students to help examine grapes in Napa and Sonoma counties and analyze how much exposure to harmful compounds renders the grapes tainted. Although the federal grant may help answer some of the vintners' questions, it's not enough, she said, to cover them with the urgency deserved.

"When you divide (the grant) across three states and four years, then suddenly it's not that much money anymore," Oberholster said. "It limits the amount of progress you can make."

With more funding, Oberholster said they could expand their trials beyond the Napa and Sonoma region — and likely speed up the time it will take to find solutions for vintners.

"I know that there are a lot of very important issues out there but the wine and grape industry is an important one for California," she said. "I think they deserve more attention."

The economic impact of California's wine industry

California produces more than 80% of the wine made in the U.S. The state's wine and grape sector contributes $73 billion annually to California's economy, according to a 2022 report commissioned by the Wine Institute and the California Association of Winegrape Growers.

But the state's wine regions, known for their ideal grape-growing climates, are now routinely facing threats of wildfires.

Damage caused by fires in 2020 — when an unprecedented burst of August lightning strikes sparked catastrophic wildfires across the state — cost California's wine industry as much as $3.7 billion, according to an estimate from former wine industry executive Jon Moramarco, owner of the market research firm bw166.

The re-introduction of Aguiar-Curry's bill comes as the state is eyeing a projected $22.5 billion budget deficit, which means any new funding request will be scrutinized closely. Even so, the Assembly member said she will be working hard to educate her colleagues on the industry's value and the importance of additional research.

"This industry employs thousands of people — the growers, producers, those trucking and shipping the products," she said. "We want to help keep these people employed and give people the best-quality products."