UC Cooperative Extension (UCCE) researchers have been closely examining smoke damage in vineyards, following the significant wildfires in Northern California in recent years. A new study on the issue highlights wind as a significant factor in damage levels, along with temperature, time of the season, and proximity to an active wildfire. There is significant concern surrounding smoke taint in winegrapes, as millions of dollars’ worth of grapes have been either left in the fields or sold as a substantial discount due to the stigma associated with smoke taint.
The study examined the effect that distance and elevation can have on potential taint in winegrapes in relation to smoke exposure. While vineyard elevation did not have an impact on grape quality, vineyards immediately downwind near wildfires had high concentrations of the compounds affecting flavor in the grapes. Vineyards further away from active fires were less affected, as the smoke dissipated enough to not be harmful.
Samples were taken from 14 vineyards in areas of Lake County that experienced smoke exposure and were analyzed and made into small batches of wine. The combination of volatile phenols and glycosides is what is responsible for creating the smell and taste that are associated with smoke taint. A panel of wine industry professionals sampled the wines and found that smoke compounds in a concentration of fewer than six micrograms per liter were difficult to taste in the testing.
The study determined that the intensity of the smoke, duration of exposure and timing in the season are the most influential factors in determining smoke damage. The fruit is essentially more at risk to damage the closer it is to harvest time when grapes are exposed to wildfire smoke. The effort to establish a standard for accurately measuring the effects of smoke on blocks of vineyards may be challenging as the study found no uniformity to the smoke damage that occurred in the sampled vineyards.