Bacteria on Grapevines Offer Hope Against Wildfire Smoke Damage in Wine

Researchers have discovered that a naturally occurring bacterium found on grapevines may help winemakers combat the ashy aftertaste that develops in wine when grapes are exposed to wildfire smoke. The study, published October 1 in PLOS One, identifies a gene in the bacterium Gordonia alkanivorans that enables it to break down guaiacol, one of the main volatile phenols responsible for the smoky flavor known as “smoke taint.”

The bacteria live on the surface of grape leaves and on the fruit’s skin. Scientists believe that harnessing these microbes could offer a targeted way to neutralize smoke taint before it affects the taste of wine. This research comes at a time when wildfires are becoming more frequent and severe, especially in major wine-producing regions like California and Oregon. In 2020 alone, winemakers in these states lost more than $3 billion due to smoke damage and unusable grapes.

Tom Collins, a grape and wine chemist at Washington State University, explained that wildfires now affect vineyards somewhere in the western United States or British Columbia almost every year. He emphasized the need for new tools to address this growing problem.

Wildfire smoke contains volatile phenols that can penetrate a grape’s waxy skin. While grapes initially mask these compounds by attaching sugars to them, the fermentation process later breaks down this sugary coating, releasing the smoky flavors into the finished wine. This makes smoke taint difficult to detect until after winemaking is underway.

To investigate how bacteria might help, Collins and his team collected leaves from chardonnay and cabernet sauvignon vines. They isolated bacteria from these samples and grew them in petri dishes with different energy sources: glucose, guaiacol, or nothing. Two strains of G. alkanivorans thrived when fed only guaiacol, turning bright orange as they grew. Genetic analysis confirmed their identity.

The researchers measured how quickly each strain broke down guaiacol over four days. After 96 hours, almost no guaiacol remained in either dish. However, when given other smoky compounds similar to guaiacol, the bacteria did not grow, suggesting that different strains may be needed to tackle other contributors to smoke taint.

The team also pinpointed the gene responsible for guaiacol degradation. When they deleted this gene from one strain, it lost its ability to consume guaiacol.

Current methods for removing smoke taint from wine often have unwanted side effects. For example, filtering wine with activated charcoal can strip out not only smoky compounds but also desirable elements like color and flavor. Cole Cerrato, a researcher at Oregon State University who was not involved in the study, said that using bacteria could offer a more precise solution without harming wine quality.

Despite these promising results, guaiacol is just one of many volatile phenols linked to smoke taint. Collins noted that further research is needed to explore other members of the grapevine microbiome and their potential to break down additional ashy compounds. The findings open new possibilities for protecting wine quality as wildfires continue to threaten vineyards across North America.