Understanding Smoke Exposure Results: Pinot noir Baseline Concentrations of Smoke Impact Markers across Five Vintages

Goals: With increased wildfires in recent years, winemakers now regularly need to interpret results from analyses for smoke related marker compounds to determine if smoke intrusion has impacted their wines. The goal of this study was to examine naturally occurring baseline levels of smoke exposure marker compounds in un-oaked Pinot noir to enable winemakers to better understand smoke exposure results. This study also sought to understand how baseline concentrations of smoke marker compounds change from year to year.

• Pinot noir wines from California and Oregon had detectable baseline levels of free and bound marker compounds, including guaiacol, 4-methylguaiacol, 4-ethylphenol, and, m-, p-, and o-cresol. In 2019, the baseline free guaiacol concentration ranged from 1.2–2.3 µg/L, while total (free and bound) guaiacol ranged from 6.4–12.0 µg/L.

• The concentration of free guaiacol was greater in older vintages, while total guaiacol largely did not change from year to year.

• The ratio of free to total guaiacol approached 1:2 after 5 years, suggesting baseline guaiacol may approach an equal ratio of free to bound over time.

Impact and Significance: While baseline levels identified here were low, winemakers should become familiar with the baseline concentrations in their wines to better understand risk during smoke impacted vintages. With increased analysis of non-smoke impacted, baseline samples, it may be possible to create a risk matrix by wine variety for smoke exposure. Additionally, as wines age, free volatile smoke marker compounds may increase due to normal changes to baseline compounds and may not always represent smoke-related glycosides releasing free volatiles.