In partnership with the Napa Valley Grapegrowers, ETS Laboratories has been building a database of grape samples to help growers and winemakers better understand smoke impacts on winegrapes, work with insurance companies to protect their assets, and create individual baselines for the varieties in their vineyards. Since the program launched in 2021, this effort has helped to inform the global methodology around smoke taint testing.

Following the catastrophic wildfires of 2020, the winegrowing community expressed interest in an extended list of analytical markers of smoke exposure, however two challenges were identified.

The first challenge was with a class of markers known as “glycosylated” or “bound” compounds. Until the Fall of 2020, reference standards were not available for these types of compounds, and there was not consensus between specialists about which ones to measure.  ETS Laboratories worked with the Wine Institute Technical Committee, the Australian Wine Research Institute (AWRI), and major wineries to establish a common list for these markers, as well as facilitate and fund the production of analytical standards. These reference standards are now available, allowing testing laboratories worldwide to produce comparable results for glycosylated markers.

The second challenge was that compared to the well-established markers of smoke exposure guaiacol and 4-methylguaiacol, additional volatile markers and glycosylated markers tend to be naturally present in measurable amounts in grapes not exposed to smoke. Evidence of smoke exposure is no longer provided by “positive” lab test results, but by whether or not amounts exceed naturally occurring levels. Answering this question is only possible if a large database of grape samples not exposed to smoke, covering major varieties over multiple vintages, is available.

The Napa Valley Grapegrowers leveraged Extension Risk Management Education (ERME) grant funding to cover the cost of 150 extended volatile and glycosylated markers panels, increasing accessibility for producers and helping to build the largest grape sample library in the world. The Napa-based non-profit also leveraged its deep roots in the community to connect producers to the program, sharing its lasting benefits and the financial assistance available for them to join.

In testing for these volatile and glycosylated compounds, one can determine if their grapes may have existing levels present prior to a smoke event, and therefore can compare the compound levels to their individual baselines following a smoke event. Proactively collecting samples before a smoke event to get that baseline may be critical when working with insurance providers not if we experience another significant fire event, but when we do. Climactic pressures are making farming increasingly difficult. Climate education, wildfire resiliency, and preparedness is central to Napa Valley Grapegrowers leadership efforts; they utilize scientific rigor and education to best prepare their farming community for the challenges that come its way.

This program found that reportable levels for guaiacol were extremely rare for most grape varieties, and not observed for 4-methylguaiacol in any variety. However, as expected with Syrah, guaiacol was present in almost 80% of samples tested, and the same is true for its main glycosylated form guaiacol rutinoside. Interestingly, low levels of guaiacol were reportable in a couple other varieties tested. Most of the “positive” samples, however, were observed after light haze from distant wildfires had been experienced in most growing areas, which casts doubts about the “natural” origin of these low levels. Additionally, low ppb levels were frequently observed for some of the additional volatile markers and most of the glycosylated markers. These levels appear consistently with those reported elsewhere (AWRI).

There is incredible research being conducted at universities and labs around the world, but in 2021 ETS and NVG identified the opportunity to address the knowledge gap in a localized way. This has, in turn, helped to inform the global methodology for wine grape smoke exposure testing, as well as engaged Napa Valley growers in implementing best practices related to baseline sample testing. Nonetheless, there are still a lot of unknowns in this field that continued academic research aims to address, such as current research at UC Davis, which secured its funding with Congressman Thompson’s final 2023 appropriations government funding bill.

As a best practice, the Napa Valley Grapegrowers recommends that growers freeze baseline samples or send them to a laboratory, so they can compare before and after smoke exposure events year over year. NVG has released best practices videos to the public, available in both English and Spanish, containing additional information on best practices and results from this research.