Smoke & Winegrapes: A Conversation with Glenn McGourty

With major wildfires occurring every year in California, winegrape growers and buyers are obviously concerned about the effect of smoke on vineyards. Do wildfires necessarily mean problems for vineyards?

Glenn McGourty pressing small lots of wine for testing the impact of smoke. Photo credit: UCANRWorking in collaboration with the Lake County Winegrape Commission, UCCE Viticulture Farm Advisor Glenn McGourty set out to answer that question.

“It can be difficult to determine if fruit has been compromised in quality when exposed to wildfire smoke, and whether or not smoke flavors will result when wine is fermented,” McGourty says. Among the factors that play a role are the vineyard’s proximity to an active fire, wind direction and speed, and air temperature.

To study this issue, McGourty formed a workgroup of local growers and winemakers with Anita Olberholster, UC Cooperative Extension enology specialist in the Department of Viticulture & Enology at UC Davis. The team analyzed 14 lots of wine from Lake County vineyards and one control lot from Napa. They focused on the presence of volatile phenols and glycoside compounds in the finished wine.

Tasters found it difficult to detect off flavors in wines with less than 6 micrograms per liter of guaiacol. And his team concluded that 6 to 10 micrograms per liter resulted in detectable smoke flavors in the wine, but levels below that threshold were unlikely to have an impact on wine quality.

McGourty says that sampling winegrapes close to harvest, performing micro-fermentations, and running a guaiacol lab analysis is a good way of determining whether smoke from wildfires is likely to damage the final product.

To learn more, view the video below.


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