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Summary 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. Key Findings: 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.

Adjusting the soluble solids of the prefermentation must is a tool by which winemakers can manipulate the flavor profile of a wine. Brix, a measure of soluble solids, is often modified prior to fermentation by chaptalization or the addition of water, but also can be modified in the vineyard by allowing the fruit to further mature on the vine. This work presents the effects of harvest maturity and prefermentation Brix on the flavor profile of Cabernet Sauvignon (CS) and Syrah (SY) wines. Fruit from each cultivar were harvested at three approximate maturity targets: 20 Brix – unripe, 24 Brix – ripe, and 28 Brix – overripe. Must from each harvest was first divided, and then the Brix was adjusted to match each of the target maturities, e.g. portions of the 24 Brix harvest were adjusted to 20 and 28 Brix. Descriptive analysis found 10 attributes which significantly varied among the CS wines and 14 attributes which significantly varied among the SY wines. Harvest maturity primarily impacted the CS aroma profile, as wines produced from unripe fruit showed increased green aroma, but wines produced from ripe/overripe fruit showed increased jammy berries aroma. Increasing the prefermentation Brix of the CS must increased the intensity of bitterness, hotness, and viscosity, but decreased the sourness. The SY wine flavor profile was heavily impacted by increasing the prefermentation Brix, which showed higher intensities of astringency, ethanol aroma, hot mouthfeel, jammy fruit aroma, rose aroma, solvent aroma, ethanol aroma, and viscous mouthfeel. The SY Fruit maturity showed a significant on the astringent intensity and earthy aroma, but an interactive effect between harvest maturity and Brix was found for sulfur, cabbage aroma, and bitterness.

Summary Goals: The goal of this project was to determine the impact of sulfur dioxide (SO 2 ) and berry maturity on the color of Syrah rose wines through fermentation and accelerated aging. This project also set out to determine the best method for measuring potential color of rose wines by measuring anthocyanin bound to SO 2 . Key Findings: Acetaldehyde was found to be the most suitable reagent for reacting with SO 2 bound to anthocyanin and releasing “potential color” of rose wines. Color in rose wines was affected by fruit maturity and decreased during fermentation. SO 2 treatment had no impact on rose color by the end of fermentation. During aging, absorbance at 520 nm increased over time and was affected by fruit maturity and SO 2 treatment. Final absorbance at 520 nm after eight weeks of accelerated aging was accurately predicted by a reaction with acetaldehyde prior to aging. When analyzed with tristimulus color measurements, fruit maturity and SO 2 content affected visual intensity of red and yellow hue over time. Impact and Significance: This study provides winemakers with tools to measure apparent and potential color in rose wines. In both 22 and 24 Brix fruit, wines retained only 38 and 27%, respectively, of the initial color by the end of fermentation. The level of SO 2 added to wine had no impact on postfermentation color, but levels of SO 2 added prior to aging did impact long-term color. The potential for a rose wine to darken over time was influenced by how much color the wine initially had, and SO 2 concentrations had a larger impact on color development in wines with more color initially.