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Smoke taint Symposium
Assessment and Management of Risk Associated with Wildfire Smoke Exposure of Grapes in the Vineyard
June 17, 2025 | 9:00 am – 5:00 pm | Location: De Anza Ballroom III (Portola)
This symposium will provide an overview of a systems approach to vineyard monitoring and comprehensive update on research into all aspects of the impact of wildfire smoke exposure to wine grapes by leading researchers in air quality modeling, viticulture and physiology, enology and sensory evaluation. Topics will include an evaluation of barrier sprays and smoke composition according to fuel source, evaluation of modeling frameworks to simulate atmospheric smoke-taint conditions in the western US, smoke emissions, atmospheric aging, and deposition, dose-response smoking trials and vineyard mitigation practices; sensing potential to detect smoke impacts on vine function and berry composition; decision support tools for vineyards threatened by wildfire smoke, scaling up small-scale fermentations and consumer preference of smoke impacted wines. The symposium promises to reveal impactful research findings and provide opportunities for discussion with researchers.
ASEV dedicates the Smoke Taint Symposium to Anita Oberholster from the University of California, Davis. She made significant contributions to the study of smoke taint in wine grapes.
Symposium
Symposium Chair:
Elizabeth Tomasino, Oregon State University, Corvallis
Program:
Program is subject to change.
| 9:00 am – 9:15 am | A Systems Approach Vineyard Monitoring Elizabeth Tomasino, Oregon State University, Corvallis |
| 9:15 am – 9:45 am | Smoke Emissions, Atmospheric Aging, and Deposition in California Mike Kleeman, University of California, Davis |
| 9:45 am – 10:15 am | A WRF-Chem-HYSPLIT Modeling Framework Simulating Atmospheric Smoke-Taint Conditions in the Western US Ana Carla Fernandez Valdes, Washington State University, Pullman |
| 10:15 am – 10:45 am | Break |
| 10:45 am – 11:15 am | Dose-Response Smoking Trials and Vineyard Mitigation Practices Alec Levin, Oregon State University, Central Point |
| 11:15 am – 11:45 am | Managing Smoke in the Vineyard: Evaluation of Fuel Sources and Barrier Sprays Tom Collins, Washington State University, Tri-Cities |
| 11:45 am – 12:15 pm | Proximate Sensing Potential for Detecting Smoke Impacts on Vine Function and Berry Chemistry Beth Forrestel, University of California, Davis |
| 12:15 pm – 1:15 pm | Box Lunch Included |
| 1:15 pm – 1:45 pm | Decision Support Tools for Vineyards Threatened by Wildfire Smoke Amod Sugiyama, Oregon State University, Corvallis |
| 1:45 pm – 2:15 pm | Smoke Perception Thresholds and Understanding the Consumer Response to Smoke Taint Jenna Fryer, Oregon State University, Corvallis |
| 2:15 pm – 2:30 pm | Break |
| 2:30 pm – 3:00 pm | Relating Grape and Small Fermentation Smoke Data to Production Scale Outcome Tom Collins, Washington State University, Tri-Cities Elizabeth Tomasino, Oregon State University, Corvallis |
| 3:30 pm – 4:00 pm | Panel Discussion Q/A Tom Collins, Washington State University, Tri-Cities Mike Kleeman, University of California, Davis Alec Levin, Oregon State University, Central Point Elizabeth Tomasino, Oregon State University, Corvallis |
| 4:00 pm – 5:00 pm | Poster Session and Reception |
| P1 | Rapid Detection and Risk Assessment of Smoke-Derived Volatile Phenols: A Chemometric Approach using Spectrofluorometry Brandt Bastow, University of California, Davis |
| P2 | Non-contact Post-fermentation Wine Processing to Remove Thiol-Related Smoke Compounds Lik Rong Lim, Oregon State University, Corvallis |
| P3 | Selective Adsorption of Free Volatile Phenols Using A Synthetic Resin Connor Patton, University of California, Davis |
| P4 | Barrier Spray Analyses for Mitigation of Smoke-Related Volatile Phenols in Cabernet Sauvignon Grapes Gauthier Lagarde, University of California, Davis |
| P5 | Impacts of Methyl Jasmonate and Benzothiadiazole on Glycosylated Phenols in Grapes Exposed to Smoke Marker Compounds Chen Liang, University of California, Davis |
| P6 | Validation of Protocols for Acid Hydrolysis of Smoke Related Glycosides Julie Hilland, Washington State University, Tri-Cities |
Brandt Bastow* | Adam Gilmore | William Drayton | Anita Oberholster
Rapid Detection and Risk Assessment of Smoke-Derived Volatile Phenols: A Chemometric Approach using Spectrofluorometry
Brandt Bastow,* Adam Gilmore, William Drayton and Anita Oberholster
*University of California, Davis, 677 Laugenour Dr., Woodland, CA, 95776, bpbastow@ucdavis.edu
The 2020 wildfires on the United States West Coast highlighted the urgent need for rapid, cost-effective methods to assess smoke exposure in wine. Analytical laboratories were inundated with samples, delaying results by over a month—an impractical timeframe for harvest decisions. Current assessment methods rely on mass spectrometry, which is accurate, but time-intensive and costly. To address these challenges, this research explores absorbance-transmission and excitation-emission matrix (A-TEEM) spectroscopy combined with chemometric modeling as a rapid alternative to quantify smoke-derived volatile phenols and their associated sensory risks. The study involves analyzing wine samples from multiple Northern California vineyards, spanning 10 varietals and several vintages. Sample preparation includes linear dilutions of severely smoke-affected grapes and wines to enhance detection of trace absorbance and fluorescence spectral signatures. Sensory analysis was conducted to determine the levels of various “smoke taint” attributes present in the wine. Single and multi-block chemometric models, employing multivariate and machine learning techniques, are currently being constructed by regressing A-TEEM spectral data against mass spectrometry and sensory analysis reference values. Statistical approaches under evaluation include gray classical least squares, parallel factor analysis, multivariate curve resolution, partial least squares, locally weighted regression (LWR), and extreme gradient boosting. Preliminary results demonstrate strong predictive correlations, with a LWR model achieving an R² of 0.997 for free guaiacol. A-TEEM demonstrates high instrumental repeatability (RSD < 2%), supporting the method’s robustness. This research aims to establish the efficacy of spectrofluorometry as a reliable, cost-effective tool for smoke taint risk assessment, enabling producers to make timely, informed decisions during wildfire-affected harvests.
Funding Support: CDFA 2021 Multi-State Specialty Crop Program
Lik Rong Lim | Elizabeth Tomasino*
Non-Contact Postfermentation Wine Processing to Remove Thiol-Related Smoke Compounds
Lik Rong Lim and Elizabeth Tomasino*
*Oregon State University, 100 Weigand Hall, Corvallis, OR, 97331, elizabeth.tomasino@oregonstate.edu
Global warming and climate change have increased the number of wildfire events during the grapegrowing season. The smoke-exposed grapes can result in smoke-tainted wines, which are perceived poorly by the consumer. Volatile thiophenols contribute to the ashy and smoke-tainted off-flavors in wine. Traditional sulfur mitigation methods for wine include adding copper sulfate as a fining agent which partly remains in the wine after bottling. However, copper sulfate is traditionally used on reductive related sulfur compounds and has yet to be thoroughly evaluated for removing volatile thiophenols in wine. It is also known to alter other wine aroma compounds. This work was done on a benchtop scale, with the goal of removing thiols without having the product come in contact with the wine and selectively removing only smoke compounds. An inert closed-loop system was devised, where thiophenols could be removed from the initial solution using a separate flask containing a thiol-selective trapping compound, – 5,5’-dithiobis(2-nitrobenzoic acid) (DTNB). This system ensured the trapping solution would not mix with the initial solution/wine. Previous work investigated the parameters suspected to influence trapping efficiency, including the concentration of thiol, the concentration of DTNB, the size and number of bubbles, the buffer solution used, and the temperature. The system is now being evaluated with a model wine spiked with smoke thiols to evaluate the trapping feasibility of the system. Future work includes testing on smoked-out wines and conducting sensory evaluations to determine if removing volatile thiophenols improves the perceived overall quality of the wine by consumers.
Funding Support: the USDA-Agricultural Research Service (ARS) project number 2072-21000-057-00D.
Connor Patton*
Selective Adsorption of Free Volatile Phenols Using A Synthetic Resin
Connor Patton*
*University of California, Davis, 2949 Portage Bay West, Apt 125, Davis, CA, 95616, cqpatton@ucdavis.edu
Wildfire smoke exposure of winegrapes leads to wines with an unappealing, ashy flavor and aroma. The ashy flavor and aroma is caused by the absorption of smoke-related volatile phenolic compounds into the skin of the grapes. Treatment of smoke-tainted wines involves the introduction of microporous synthetic resin. The resin is intended to selectively adsorb volatile phenolic compounds such as guaiacol, syringol, phenol, and cresols while limiting the removal of wine matrix compounds necessary to preserve the wine’s natural flavor, color, and texture. Addition of the synthetic resin to smoke-tainted California red wines for 1 hr with stirring resulted in 49 to 95% removal of free guaiacol; 4-methylguaiacol; o-cresol; 4-ethylguaiacol; p-cresol; m-cresol; 2,3-dimethoxyphenol; 4-ethylphenol; syringol; and 4-methylsyringol; and 18% removal of free phenol. The glycosidically-bound phenolics were only reduced in concentration by 36% reduction or less. Ethanol content of treated wines only dropped by 0.4%, indicating limited competitive adsorption between ethanol and the volatile phenols. Future research will investigate the effect of resin treatment on other volatile compounds of wine. The current findings indicate the potential of the resin as a viable material for smoke-taint amelioration. Further research will be performed to assess the viability of modifying the resin structure and composition to increase the adsorptive capacity and selectivity of the resin. For the research to be applicable in an industrial setting, the smoke-taint amelioration process will have to be continuous and capable of scaling up to an industrial volume. The findings of this study will demonstrate the capability of this material to remove the smoke effects from wildfire smoke-tainted wines and the potential for doing so on an industrial scale.
Funding Support: California Department of Food and Agriculture
Gauthier Lagarde*
Barrier Spray Analyses for Mitigation of Smoke-Related Volatile Phenols in Cabernet Sauvignon Grapes
Gauthier Lagarde*
*UC Davis, 595 Hilgard Ln, Department of Viticulture and Enology, Davis, CA, 95616, glagarde@ucdavis.edu
Wildfires are a growing concern for the wine industry, as smoke-derived volatile phenols can significantly alter the sensory profile of wine, imparting undesirable smoky aromas and an ashy aftertaste. Smoke-tainted wines are thus compromised in flavor, typicity, and consumer acceptance. This study evaluates the effectiveness of Kaolin and GM3E as barrier sprays against smoke exposure. Whole grape bunches from 10 potted Cabernet Sauvignon vines were immersed in the respective spray solutions for 30 sec, with the sprays also applied to the leaves. Water was used for two control groups. The following day, three groups of vines (Kaolin, GM3E, and one control) were subjected to 4 hr simulated smoke exposure. The remaining control group was not exposed to smoke (negative control). One week after exposure, the grape bunches were collected and cleaned with water. The washed grapes and cleaning water were stored at -20°C. Free and total volatile phenols in the grapes and cleaning water were quantified by gas chromatography-mass spectrometry, while individual glucoside-bound volatile phenols were measured by liquid chromatography-mass spectrometry. Preliminary results show distinct differences between Kaolin and GM3E. GM3E treatment resulted in higher concentrations of free volatile phenols (337 µg/L) compared to the smoked control (184 µg/L). Kaolin showed lower levels (144 µg/L) than the smoked control, but still higher than the non-smoked control (34 µg/L). The distribution of volatile phenols also varied by treatment. For total volatile phenols, GM3E exhibited 9% of 2,3-dimethoxyphenol, while other treatments had less than 0.6%. Cleaning water contained more total volatile phenols in the GM3E treatment (53 µg/L) than in Kaolin (34 µg/L), smoked control (24 µg/L), or control (9 µg/L). These results suggest barrier sprays can alter the concentration and distribution of smoke-related phenols, providing insights into mitigating wildfire smoke effects on wine quality.
Funding Support: California Department of Food and Agriculture (CDFA)
Chen Liang* | Arran Rumbaugh | Ron Runnebaum | Francesco Maioli
Empacts of Methyl Jasmonate and Benzothiadiazole on Glycosylated Phenols in Grapes Exposed to Smoke Marker Compounds
Chen Liang,* Arran Rumbaugh, Ron Runnebaum and Francesco Maioli
*University of California, Davis, 595 Hilgard Ln, RMI North, Davis, CA, 95616, chelian@ucdavis.edu
During a wildfire event, smoke-exposed grape berries can uptake volatile phenols (VPs) such as guaiacol, cresols, and syringol. These smoke-taint related compounds can be metabolized into their glycoconjugates (Gly-VPs), transported, and stored in the grape cells. The Gly-VPs can be hydrolyzed during fermentation, wine aging, and consumption, releasing the VPs. The hydrolysis of Gly-VPs in mouth was reported to relate to the “smoky”, “ashy” off-flavor. Variations in grape Gly-VPs after smoke exposure were reported to improve evaluation of smoke taint risk. This study investigates the effects of human interventions in the vineyard after smoke exposure on Gly-VPs variation in grapes, seeking a way to mitigate smoke taint accumulation in grapes. Glycosylation of the VPs is a detoxification process of the grapevine. Application of natural or synthetic compounds can enhance plant defense responses and affect secondary metabolic pathways. Two such compounds are methyl jasmonate (MeJ) and benzothiadiazole (BTH). Both compounds were found to increase the phenolic content of grapes. This metabolic change could increase glycosylation of VPs, the same as for anthocyanin formation. Alternatively, formation of Gly-VPs could be decreased due to increasing glycosylation of endogenous phenols. To study the effects of MeJ and BTH on Gly-VPs variation in grapes, Cabernet Sauvignon grape clusters were exposed to aqueous mists of smoke marker compounds (guaiacol, p-cresol, syringol) at early postveraison. MeJ and BTH spray mists were applied one day after exposure, alone and in combination. Berry samples were collected at three time points. The glycosylated smoke marker compounds of each VP were detected in berries at harvest. The concentrations and changing dynamics of Gly-VPs in berries with MeJ and BTH applications will be reported and preferential uptake of the exposed three VPs will be documented.
Funding Support: USDA-ARS
Julie Hilland* | Thomas Collins | Robert Coleman
Validation of Protocols for Acid Hydrolysis of Smoke-Related Glycosides
Julie Hilland,* Thomas Collins and Robert Coleman
*Washington State University, 359 University Drive, Richland, WA, 99354, julie_hilland@wsu.edu
Wines produced from smoke-exposed grapes can exhibit undesirable sensory and palatable characteristics. The negative financial impact on a global scale for both grape and wine quality requires reliable methods to measure “free” volatile phenols (VP) and “bound” (VP-glycosides) in grapes and wine when evaluating smoke impact severity. Many analytical methods exist for gas chromatography-mass spectrometry (GC-MS) to quantify volatile phenols. These can also be applied to measuring VP-glycoside samples subjected to acid hydrolysis. However, there is currently no standard protocol for acid hydrolysis. This has contributed to inconsistent analysis results as protocols vary in application of acid, temperature, and duration. This project will develop and validate an acid hydrolysis approach to quantify VP and VP-glycosides in smoke-affected wines. A 30-L batch of model wine containing 5g/L KHTA and 14.75% alc (v/v) and adjusted to pH 3.30 was prepared. The amount of acid required to adjust samples to pH 1.0 and the amount of base to bring samples back to pH 3.5 was determined. Ten volatile phenols were added at 50 ug/L concentration each to the 30-L batch. VP-model wine samples were divided into two main categories: control and acid hydrolyzed. Samples were further divided into two subgroups: heated/non-heated and covered (watch glass)/uncovered. A hot water bath set at 80°C was used as the heating source. Unheated samples were placed on the laboratory counter at room temperature. Hydrolysis was conducted over a 4-hr period. Volatile phenol recovery using GC-MS was used to quantify and evaluate method success based on percent recovery. All tests were conducted in triplicate. The extent of variability across treatments will be used to improve acid hydrolysis protocols. Once validated, establishment of optimal pH, temperature, and time parameters by characterizing the hydrolysis reactions of known glycoside concentrations can be determined.
Funding Support: USDA/SCRI
This work is supported by the Specialty Crop Research Initiative, project award no. 2021-5118-35862, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.
