As wildfires increase in frequency and severity, they are taking a significant toll on the wine industry. Volatile compounds in the smoke can be absorbed by grapes and produce an unpleasant taste known as “smoke taint” in the wines made from such grapes. A new study led by the University of California, Santa Cruz provides practical guidelines for using biomarkers to identify grapes and wines affected by smoke taint.
Previous studies have associated smoke taint with volatile phenols that are present in the smoke produced by burning vegetation. These chemical compounds are absorbed through the skin of ripening grapes and, through binding with sugars, they form nonvolatile compounds called phenolic diglycosides. Although in their bound state, these compounds cannot be smelled or tasted, foul-tasting free phenols can be released by enzymes, either during the fermentation process or in the mouth by the enzymes present in saliva.
“We found that the phenolic diglycosides are stable in cabernet sauvignon during bottle aging, but then during tasting the monomers that smell bad get released in the mouth,” said study lead author Phillip Crews, a distinguished research professor of Chemistry at UC Santa Cruz.
By using sophisticated methods such as ultra-high-performance liquid chromatography and quantitative mass spectrometry, Professor Crews and his colleagues have provided some of the first quantitative measurements of phenolic diglycosides in premium California and Oregon grapes and wines that were exposed to six different levels of natural wildfire smoke.
“There are still major gaps in our understanding of these compounds, so more research is needed. But people can use these procedures now to look at a bottle of wine or a batch of grapes and tell if it’s likely to be affected by smoke taint,” explained Professor Crews.
“This research is highly valuable, with the potential to save countless dollars, and is increasingly relevant in our world of drought and climate change,” said Eleni Papadakis, a winemaking consultant from Portland, Oregon, who was not directly involved in the study, but helped connect the researchers with Oregon winemakers and participated in frequent discussions. “I believe I speak for the whole of the winemaking community when I express the excitement and appreciation for the strong data and evidence-based guidance Professor Crews and his team have provided with this groundbreaking work,” she concluded.
The study is published in the Journal of Natural Products.
By Andrei Ionescu, Earth.com Staff Writer