Can barrier sprays reduce smoke impacts? Since 2020, Washington State University wine science professor Tom Collins has been testing barrier sprays, including this kaolin clay, against smoke exposure at a research vineyard at WSU’s Irrigated Agriculture Research and Extension Center in Prosser. The product — and others — shows promise, but more research is needed. (Kate Prengaman/Good Fruit Grower)
Can barrier sprays reduce smoke impacts? Since 2020, Washington State University wine science professor Tom Collins has been testing barrier sprays, including this kaolin clay, against smoke exposure at a research vineyard at WSU’s Irrigated Agriculture Research and Extension Center in Prosser. The product — and others — shows promise, but more research is needed. (Kate Prengaman/Good Fruit Grower)

Smoky skies stayed mostly away from Washington state’s 2022 wine grape crop, but solving the problem that wildfire smoke poses for grapes and wine remains a top and urgent research priority of the state’s wine industry. The Washington State Wine Commission is involved in several aspects of smoke research, from funding studies within the state and participating in a multistate, federally funded project, to providing input to the new smoke research program of the U.S. Department of Agriculture.

Additionally, the wine commission and Washington Winegrowers Association are members of the West Coast Smoke Exposure Task Force that represents growers and wineries from California, Oregon and Washington. The task force was formed in 2020 to combine research efforts and unify industry work on crop insurance and contracts. The task force coordinated development of extension resources and tools for growers and wineries, such as sampling and microfermentation protocols, and sponsored two smoke summit meetings and webinars to bring growers and wineries together to share problems and solutions. The task force also provides stakeholder input to the USDA as it establishes its new smoke research program.

Wildfires are a major threat to the grape and wine industry, because persistent exposure to smoke can compromise the quality and value of wine grapes and adversely affect wine. If grapes are exposed to smoke at high enough levels and for a long enough time, smoke volatile phenols can be absorbed into the berries. Smoky aromas come from a range of volatile phenols that can bind to sugars, called glycosides, in the grape and other compounds in the skin. During fermentation and aging, the smoke compounds can be released from their bound form, which can result in unmarketable wine due to “campfire” and burnt flavors and aromas.

Complicated issue

Smoke research has proved to be quite complicated. Numerous factors influence the degree of undesirable smoke aromas and flavors that can end up in wine made from smoke-exposed grapes. How far did the smoke travel? Was the smoke “fresh” with origins nearby, or did it have time to degrade? What type of plant material was burned? What grape cultivar was exposed? Grapes contain naturally low levels of phenols and glycosides, and each variety has a different sensitivity to smoke. Moreover, consumer perception and sensitivity to smoke aromas varies widely. Australia has yet to fully solve the problem after supporting smoke research for more than two decades. 

Leveraged research

Washington’s wine industry was among the first in the United States to commit research funding to better understand the impact of smoke on grapes and wine, with grants to support Washington State University research in 2016. At the time, many saw smoke events as isolated and regional, and not a high priority. Tom Collins, grape and wine chemist, leads the WSU smoke exposure research program. His initial focus was to develop portable hoop houses to simulate smoke events at WSU’s research vineyard in Prosser. This was a critical research step because it set up future trials that could be replicated, with controls, on an annual basis and has provided a steady stream of fruit for research winemaking, even in years without smoky skies. Since then, others have utilized his hoop house concept, and research efforts have expanded into a coordinated research program between Oregon State University, the University of California, Davis, and WSU.

The Washington wine industry’s support of Collins’ early work also helped leverage additional research funds, including $243,000 from the Washington State Department of Agriculture’s Specialty Crop Block Grant Program and a $50,000 planning grant from USDA’s Specialty Crop Research Initiative (SCRI) for the collaborative research team of WSU, OSU and UC Davis. Through stakeholder meetings, the planning grant identified current knowledge gaps and developed a robust research plan that was subsequently awarded a four-year SCRI grant in 2021 for more than $7.6 million. The project is led by the powerhouse research team of Elizabeth Tomasino of OSU, Anita Oberholster of UC Davis, and WSU’s Collins. 

Washington State University staff and students collect samples in a Cabernet Sauvignon block where barrier sprays were applied to the vines before a smoke event on Oct. 12, 2020, in a Prosser research vineyard. (Kate Prengaman/Good Fruit Grower)
Washington State University staff and students collect samples in a Cabernet Sauvignon block where barrier sprays were applied to the vines before a smoke event on Oct. 12, 2020, in a Prosser research vineyard. (Kate Prengaman/Good Fruit Grower)

SCRI discovery

The wine commission serves on the advisory committee of the multifaceted SCRI project, where the bulk of smoke research currently takes place. Objectives of the project are to:

—Develop faster and improved ways to analyze grape samples and target smoke marker compounds.

—Identify sensory thresholds in wine for different grape varieties.

—Create a vineyard sensor network to model and predict risk from smoke.

—Explore vineyard barrier sprays and coatings that prevent smoke uptake by grapes.

—Develop tools for wineries to mitigate impacted wines.

Major progress was made in the project’s first year. The research team discovered a new class of sulfur compounds, called thiophenols, that can cause smoky or ashy aromas when combined with volatile phenols. This breakthrough helps explain why some grapes with low levels of the markers previously used for testing resulted in smoky wines, while others with higher levels did not. 

The project also deployed more than 60 air quality sensors in West Coast vineyards, with more than 25 set up in Washington, and identified barrier sprays and biofilm coatings that show potential to prevent grape uptake of smoke compounds. These are under further study.

Washington State University wine science professor Tom Collins, left, and WSU winemaker Matt Boenzli walk back down the vineyard row after setting up bins for harvesting the different trial replicates. The blue line marks where the vines where intentionally exposed to smoke. (Kate Prengaman/Good Fruit Grower)
Washington State University wine science professor Tom Collins, left, and WSU winemaker Matt Boenzli walk back down the vineyard row after setting up bins for harvesting the different trial replicates. The blue line marks where the vines where intentionally exposed to smoke. (Kate Prengaman/Good Fruit Grower)

New USDA program

Thanks to the lobbying efforts of West Coast grape and wine trade associations, smoke research is also a priority of Congress. In the past four years, Congress added $5 million to USDA’s Agricultural Research Service (ARS) budget to create a new smoke research program, with half of the funds distributed to WSU, OSU and UC Davis to support ongoing smoke research. This is the start of a new and long-term mission for ARS.

Research chemist Arran Rumbaugh is the first of three ARS scientists to be hired to work on smoke research. She joined ARS last fall and is based at UC Davis.

Smoke research topics identified by ARS scientists as study areas include:

—Genetics and plant breeding.

—Grape coatings to block uptake of volatile compounds.

—Microbial treatments that use microbes on grapes to degrade or detoxify phenols.

—Methodologies for vineyard detection.

—Smoke movement in the vineyard, to aid in predictive modeling.

—Long-term effects on vineyard health and grapevine physiology from repeated smoke exposure.

The wine commission, under the umbrella of the West Coast Smoke Exposure Task Force, meets regularly with ARS to receive updates on progress and funding and to provide stakeholder input to ARS.

As outlined above, there are many entities now involved in smoke research. The Washington State Wine Commission is working to help support and guide research efforts at all levels. But most importantly, we strive to share research outcomes to ensure that all Washington growers and wineries have access to smoke research tools. We are ready and anxious to share future smoke research findings! 

—by Melissa Hansen