Understanding ashy flavor recognition thresholds in Pinot noir wines

Wildfires have become a growing concern in wine producing regions around the world. These fires produce harmful levels of smoke, that can carry volatile organic compounds over vast distances. When this smoke reaches a vineyard, grapes absorb these compounds which are then found in the resulting wine. These wines are described as having smokey, burnt and dirty flavors, not desirable for wine quality. Most concerningly, there is an ashy aftertaste that is considered a unique, negative attribute of wildfire affected wines. While volatile phenols are a known contributor to the smoke-related flavors found in smoke-affected wines, thiophenols have additionally been identified to be influential in the ashy flavor indicative of smoke taint. The aim of this work is to determine at what concentration of thiophenols will Pinot noir take on this perceptual “ashy” property. Using an adaptive staircase procedure, the threshold level of a mixture of smoke related thiophenols was determined in different styles of Pinot Noir wine containing various levels of smoke related volatile phenols (45 mg/L, 135 mg/L, 450 mg/L). Thresholds were estimated based on the fitted psychometric curves to understand the concentration of thiophenols within certain percentages of individuals thresholds. The results indicated that there were some wine style differences observed at the lowest phenol concentration, however at higher concentrations more representative of smoke exposure these differences were no longer found. Concentrations of volatile phenols at 135 mg/L are at risk of ashy recognition starting at a total thiophenol concentration of 20 ng/L, while at 450 mg/L if phenols are at risk at a total thiophenol concentration of 10 ng/L. This knowledge is imperative to winemakers and key stakeholders to be able to make informed decisions on what to do when faced with smoke-impacted vintages. Not only is the determined threshold level important but additionally understanding the wide range of sensitivities that exist within the population. As we look forward to better understanding the impact of wildfires on wines, it is vital to understand how consumers perceive these wines to be able to make sensory directed decisions to decrease waste and avoid unnecessary losses.