Study Finds Smoke Markers in Four of Five Chilean País Wines From the 2023 Fire Season

A study published Thursday in the journal OENO One found early evidence that wildfire smoke from Chile’s 2023 fire season altered the chemical profile of País wines from the Itata and Biobío valleys, adding to concerns about how increasingly severe fires can affect wine quality and sales.

The research is the first to examine smoke impact in Chilean País wines, a historic grape variety that remains central to traditional winemaking in the country. The authors compared single-variety País wines from five wineries across the two valleys, using wines from the 2023 vintage, which was exposed to major wildfire smoke, and the 2024 vintage, which came from a season with far less fire activity.

They found that four of the five 2023 wines had higher levels of volatile phenols and related glycoconjugates, two groups of compounds widely used as markers of smoke exposure in grapes and wine, than the 2024 wines from the same producers. Sensory tests also showed that the 2023 wines were rated higher for smoky aroma, although that difference reached statistical significance in only two of the five locations.

The work focused on wines made in Chile’s south-central wine regions after a severe wildfire outbreak in February 2023. According to the study, the main smoke exposure event took place between February 2 and February 15, during the late ripening period for País grapes. That timing matters because grapes can absorb smoke compounds before harvest, and those compounds can later contribute to smoky or ashy flavors in finished wine.

The researchers said the findings do not mean every 2023 País wine from the region was equally affected. They stressed that sensory results should be read carefully because wine style, vintage conditions, and cellar practices can also shape aroma and taste. Even so, the chemical results point to a measurable smoke signal in most of the sampled wines from the fire year.

The study was led by researchers from Chile and abroad, including Arran Rumbaugh, Annegret Cantu, Francisco Medina Jofré, Carola Vergara, Dietrich Von Baer, Francesco Maioli, Luis Bustamante Salazar, María Dolores López Belchí, Alvaro Castro, and Jimena Balic. It was received in January, accepted in September, and published on October 15.

For the analysis, the team collected 10 wines in total from five commercial wineries, pairing a 2023 wine made from smoke-exposed fruit with a 2024 wine made from fruit considered not affected by smoke. The wineries were located in Coelemu, Portezuelo, and Quillón in the Itata Valley and in Nacimiento in the Biobío Valley. The wines were made with comparable traditional País methods, including artisanal processing and storage or aging in raulí wood casks, although the researchers said some production details varied by winery and were not fully available.

The chemical testing measured eight volatile phenols, including guaiacol, 4-methylguaiacol, phenol, cresols, and syringol, using gas chromatography and mass spectrometry. The team also measured eight glycoconjugates, compounds formed when grapevines metabolize smoke-derived molecules, using liquid chromatography and mass spectrometry. Those methods are already used in smoke taint research in countries such as Australia and the United States.

To connect the lab results with what drinkers might notice, the team also ran a descriptive sensory analysis with 12 trained panelists from the University of Concepción. The panelists evaluated aroma, taste, and mouthfeel after seven training sessions designed to build a shared vocabulary for the wines. The stronger smoky character seen in some of the 2023 wines tracked with the higher concentration of smoke-marker compounds.

The authors said the relative ratios of volatile phenols and glycoconjugates in the Chilean wines were similar to patterns reported in Australia and the United States. That could suggest that smoke-affected wines share some common chemical signatures across producing regions, even when the local vegetation burned in the fire is different. The researchers added that more untargeted chemical work is needed to determine whether regional fuel sources leave distinct fingerprints in grapes and wine.

That question is important in Chile because the wine regions studied sit near large pine and eucalyptus plantations as well as native vegetation. The paper notes that softwoods such as pine and hardwoods such as eucalyptus can produce different smoke compositions when they burn, which may influence the mix of compounds later found in grapes and wine.

The scale of the 2023 fire season was a key part of the study’s context. The authors cited USDA and Chilean forestry data showing that 471 hectares of vineyards were burned in 2023 across affected regions. In the Itata Valley alone, according to Chile’s National Forestry Corporation, 31,012 hectares of Pinus radiata, 1,464 hectares of Eucalyptus globulus, and 18,743 hectares of native vegetation burned. In the Biobío Valley, fires consumed 58,200 hectares of pine, 53,443 hectares of eucalyptus, and 50,847 hectares of native vegetation.

By contrast, wildfire activity was much lower in 2024. The paper says only 825 hectares burned in the Ñuble Region and 5,271 hectares in the Biobío Region that season, far below the previous year. That difference gave the researchers a comparison point between a smoke-impacted vintage and a less affected one.

The study also places the findings in an economic setting that extends beyond vineyard damage. Small producers and cooperatives in Itata and Biobío reported heavy wildfire losses in 2023, and earlier estimates projected that the historic Itata Valley could lose 30% to 40% of its annual production. The authors noted that those figures did not include losses tied to smoke taint, which can make wine harder to sell even when vines and facilities are not destroyed.

That makes the findings relevant beyond academic research. For wineries, cooperatives, and labs in wine regions exposed to fires, the work adds support for using chemical screening and sensory review after smoke events, especially for traditional wines made from País. It may also help guide decisions on whether grapes or finished wines need more testing before release, a practical issue for producers trying to protect quality, pricing, and market access after a fire season.

País, known as Mission in California and Listán Prieto in Spain and the Canary Islands, was the first Vitis vinifera variety established in Chile after its introduction by Spanish settlers in the 16th century. It later lost ground to French varieties but has regained attention in recent years as a symbol of Chile’s wine heritage. The grape is widely grown by smallholders in dry-farmed vineyards, and the study notes that more than 10,000 hectares were planted nationwide as of 2022.

The authors said the results are an initial assessment, not a final word on the issue. One of the five winery pairs did not show the same clear increase in smoke markers in the 2023 wine. The researchers also acknowledged that the wines were analyzed at different ages, with the 2024 samples about a year younger at the time of testing, although they said the smoke marker compounds measured are considered stable during aging and therefore unlikely to explain the chemical differences.

Wildfire smoke has been studied extensively in other wine-producing countries, where researchers have linked it to changes in grape chemistry, lower perceived quality, and major financial losses. The OENO One paper argues that Chilean producers now need region-specific risk assessment tools, including smoke exposure mapping and management practices tailored to local grape varieties and wine styles.

In that sense, the new findings broaden the evidence base for smoke taint to a grape that had not been studied before in Chile and to a region where traditional winemaking remains economically and culturally important. They also suggest that as fires become a recurring threat, the beverage industry may need more precise analytical controls and faster post-fire decisions in the cellar to reduce the risk that smoke exposure turns into an unsellable wine.