Spray-on coatings for grapes in vineyards show promise in preventing off-flavors in wines caused by wildfire smoke exposure, according to new research from Oregon State University.

Oregon State researchers are developing a product that vineyard managers could spray onto grapes to protect them from wildfire smoke before it reaches the vines. The researchers expect the spray coating to be available within the next several years.

“Wildfire smoke is an increasing problem for wineries in the United States and around the world, and right now vineyard managers really have no tools to manage the effects of the smoke,” said Elizabeth Tomasino, an associate professor of enology at Oregon State. “This coating has the potential to transform the wine industry.”

This research was prompted by wildfire smoke that enveloped much of Oregon, Washington, California, and British Columbia in September 2020, significantly impacting wine grape quality.

The fires coincided with grape harvest time. At the time, vineyard managers were uncertain about the impact of wildfire smoke on their crop, leading many to decide that the potential impact on wine quality wasn’t worth the cost of harvest.

The smoke event resulted in more than $3 billion in losses for the wine industry, according to industry reports.

In a paper recently published in the Journal of Agricultural and Food Chemistry, Oregon State researchers led by Yanyun Zhao targeted three compounds, known as volatile phenols, that contribute to smoke taint in grapes.

Zhao, a university distinguished professor who has studied food coatings for more than 20 years, and Jooyeoun Jung, a senior researcher and assistant professor in Zhao’s lab, developed cellulose nanofiber-based coatings containing chitosan and beta-cyclodextrin that can be applied to grapes in the vineyard.

The study showed that, depending on the formulations, the films can block guaiacol and syringol and capture meta-cresol—wildfire smoke compounds that, when absorbed by wine grapes, result in off-flavors in wine.

The difference between blocking and capturing is important, Zhao said. Blocking means the coating does not absorb the phenol compounds and would not need to be washed off before winemaking. Capturing means the coating absorbs the compounds and would need to be washed off.

“Not having to wash it off saves time, money, and water for grape growers,” Zhao said. “That is what we are aiming for.”

Developing the coatings is challenging because the phenols have different chemical shapes, the researchers noted, making it difficult to create a coating that adheres properly to all the shapes to block the smoke. The researchers are continuing to refine the coating formulations and conduct cost analysis studies.

Two years of vineyard coating application studies at Oregon State’s Southern Oregon Research and Extension Center in Central Point found that the coatings do not impact the growth and quality of the grapes.

The coatings were also applied at Oregon State University’s Woodhall Vineyard outside Monroe, Oregon, where smoke chambers were placed over vines to test the smoke-blocking ability of the coatings. Wine from these grapes is currently being analyzed for quality attributes.

“Growers want something they can spray on their vines to protect them,” said Alexander Levin, a viticulturist and director of the Southern Oregon Research and Extension Center. “If this becomes commercially available, it’s going to be a big game-changer.”

In addition to Tomasino, Zhao, Jung, and Levin, the paper’s authors include Trung Tran, Lindsay Garcia, Joseph Deshields, Cole Cerrato, and Michael Penner, all from Oregon State.

The research is funded by the Oregon Department of Agriculture Specialty Crop Block Grant and the U.S. Department of Agriculture Specialty Crop Grant.

About the OSU College of Agricultural Sciences: Through world-class research on agriculture and food systems, natural resource management, rural economic development, and human health, the college provides solutions to Oregon’s most pressing challenges, contributing to a sustainable environment and a prosperous future for Oregonians. The original publication of this article can be read here.