Baseline Smoke-Taint Volatiles and Glycosides

Summary The increasing incidence of wildfires in grape growing regions of California and the West Coast has highlighted the need for enhanced understanding of the levels of volatile phenols and their non-volatile glycoside precursors that contribute to smoke taint off-flavors in grapes and wines. In this project, we measured ten volatile phenols in non-smoke exposed grapes to begin to understand baseline levels of these compounds in red and white grape varieties. Free and total levels of guaiacol, 4-methylguaiacol (creosol), phenol, 4-ethylguiacol, o-, m-, p-cresol, 4- ethylphenol, 4-methylsyringol, and syringol were measured in grapes from different regions of California. Air quality data for these regions is also presented. The data show a high degree of variability across varieties, regions, and years indicating that it will be important to have large databases to assess the impacts of smoke exposure on free and total volatile phenol composition. We have submitted a proposal to continue this work in 2022-23