Despite the claim in the initial proposal that there were no known barriers to completing this project in a timely fashion, the world conspired to make that a lie. Between March of 2020 and the end of October, on campus research at UC Davis was restricted to time sensitive research activities (“Phase 2 activities”) and was expanded to include some research that needed on site access on 30th October (“Phase 2x”). Restrictions continue regarding number of personnel, as do guidelines for high-risk employees. This was again changed when the state of California entered a second lockdown between Dec 22 to Jan 25 of 2021. It is anticipated that there is the potential for additional restrictions in on-campus access as the virus status changes.

In April, when it became clear that these restrictions would be a serious barrier, the project investigators purchased, and installed, equipment required for this project in an off-site location to allow the work to take place outside of these restrictions. This process was slowed by all the now familiar issues of operating in a COVID world. This offsite location now can run all the tests described in the original project proposal Table 3 (below) and will continue to be the research location until COVID restrictions are removed completely (UC Davis “Phase 4”)

As of December 2020, the equipment was installed and functional. The researchers are in the process of validating the equipment and proceeding on the original project’s Goal 1:

Goal 1: Standard precision tests will be done by repeated analysis with specific variations in sample, subsample, day, equipment and/or analyst to provide information on method repeatability and replicability. If adequate collaborators can be found, a reproducibility value will also be generated; if not, standard multiples of repeatability can be used as a working estimate of reproducibility.

The adjustment to the original timeline in response to this situation shows a delay of about eight months. We do not foresee additional delays due to COVID related restrictions other than any normal disruptions in deliveries or access.

One potential advantage of the new set up is the ability to increase the output of experimentation over the next several months and make up for loss of time. If that proves the case, the researchers will move onto the proposed future goals proposed in the original proposal.

Goal 4: Correlate the analytical responses of selected non-redundant tests to specific “risk” storage or transportation conditions (such as short time-extreme cold or long time- mild cold storage, with or without other extenuating conditions) which could impact the “potassium bitartrate stability” of the wines. This will determine the analytical method’s predictive abilities.

The goal of this project is to determine the volatile chemicals in smoke that affect the flavor and aroma of wine and wine grapes for Pinot noir and Chardonnay. To differentiate chemicals derived from smoke from ambient grape or wine compounds, a fuel source, barley, was chemically “tagged” using 13CO2. As 13CO2 is assimilated by the barley, it is distributed throughout the plant and its chemical components, including the precursor smoke material, such as lignin. By identifying the major components from smoke, future studies may be able to better prevent off-flavors caused by smoke from nearby wildfires. More immediate conclusions may even begin to identify thresholds when crops are exposed to smoke to the point of sensory perception prior to harvest or fermentation.

To achieve these goals, in this year we have:

• Implemented 13CO2 incubation cages for growing isotopically labelled barley (Figure 1)
• Tested and concluded ideal practical conditions to maximize growth of 13C-labelled barley
• Grew over 2 kg (dry weight!) 13C-labelled barley from January through September
• Adjusted protocols to account for Covid-19 lockdowns and personnel distancing as outlined by state and university policies, continuing the project with minimal interruption
• Begun processing and milling barley samples to determine lignin, carbohydrate, and dissolved composition through chemical methods, and 13C assimilation via isotope ratio mass spectrometry
• Designed and constructed smokers and smoke tents for smoking wine grapes using chemically labelled barley as a fuel source (Figure 2)
• Designed methodology to recreate high density smoke conditions while balancing cost[1]effectiveness of administering labelled smoke while ensuring the viability of the wine
• Exposed over 20 kg Chardonnay and 20 kg Pinot noir grape clusters to labelled smoke, consistently holding smoke labelled smoke density >20 mg/m3 over the course of 3 days in October (Figure 3)
• Made wine from grapes exposed to 13C-labelled smoke (Figures 4 and 5)

Preliminary aroma and flavor of smoke-exposed wine show a strong incorporation of chemicals associated heavily smoked grapes, with a marked difference between the grapes exposed to smoke in the tents and the control grapes that were exposed to smoke during the wildfire events in Oregon in September. Moreover, we expect to be able to differentiate the chemicals’ origins based on the NMR experiments and confirmed by GC- or LC-MS in 2021.

The overall goal of this work is to identify those compounds from smoke that cause negative impacts to wine quality. We are taking a different approach than other research on this topic. In short, we are creating label smoke compounds by growing barley (our fuel source) in a 13CO2 environment. We are then able to track the labeled carbon in the smoke, grapes and wine using NMR, which is very sensitive to 13C.

The accomplishments for the project for the 6 months has been to design the chambers needed to grow barley in elevated CO2 environments (Objective 1A). Our first barley lots (0-4) were/are being run using regular CO2 due to the expense of isotopic 13CO2. Once we have determined the optimal CO2 levels in the chambers we will switch to 13CO2. Development of the chambers included not only how to increase carbon fixation of the 13C in the plant, but determined how to measure the isotopic CO2 and other necessary plant measurements. We are on track to have 13C labeled barley to burn and produce 13C smoke for the 2020 vintage.

Research regarding smoke taint has mostly been undertaken in Australia with a focus on vine susceptibility, potential mitigation actions during winemaking to limit smoke taint expression and potential ways to remove smoke taint in the final wines. Thorough review of published smoke taint research indicated large gaps in knowledge and inconsistent results. The objective of the research project was to compare all the suggested wine protocols that evolved from the current literature using one batch of smoke impacted grapes under identical winemaking conditions except for the parameter under investigation. Results from this study will enable to us to better advice the wine industry during future smoke events. Results from this study will enable us to better advice the wine industry during future smoke events. SPME-GC-MS and UPLC-Q-TOF-MS methods employing stable isotope dilution methodology (SID) have been implemented. Cabernet Sauvignon grapes were received from three different areas with varied amounts of smoke exposure (Oakville, Alexander Valley, and Silverado Trail AVA’s) in Northern California. Gas chromatography mass spectrometry (GC-MS) and sensory analysis were performed in order to correlate wine composition to smoke taint characteristics. The winemaking variables investigated were the use of different fermentation yeasts, oak additions and fermentation temperatures. Among other attributes, smokiness and ashy aftertaste were found to be significantly different among the wines, showing a clear difference between the wines that were made from smoke impacted fruit and the control wines that were made from non-impacted fruit. One yeast showed a significant effect by highlighting the fruitiness in the wines and reducing the ashy aftertaste. Different oak additions were not successful in masking the impact of the smoke. Similarly, different fermentation temperatures did not have a significant impact on smoke expression in the resulting wines. Findings indicate that mitigation strategies during red wine fermentation have a limited impact on the extraction of smoke taint markers as well as the expression of smoke taint sensory characteristics.