Screening Potential Coating Materials to Reduce the Absorption of Volatile Phenols into Grapes During Simulated Wildfire Conditions

Wildfires release volatile phenolic compounds (VPs) that can be absorbed by grapevines, potentially resulting in “smoke taint” in wines. This has emerged as a prominent issue for the global wine industry due to negative impact on wine quality and subsequent financial losses. Since effective vineyard mitigation strategies remain limited, this study evaluated the efficacy of different materials applied to grapes to reduce the absorption of smoke marker compounds under simulated wildfire conditions. Twelve materials were applied to individual Cabernet Sauvignon clusters close to harvest. Treated vines were exposed to intentional smoke using a purpose-built tent. Grapes from treated vines, as well as smoke-exposed and non-exposed controls, were harvested at commercial maturity. The results showed a strong stratification of VPs within the tent and in the grapes. Glycosylation began within hours of smoke exposure, with significant increases in almost all glycosylated compounds within 4 hours compared to non-smoked controls. Some materials reduced VP uptake relative to untreated controls (kaolin, charcoal, and two commercial coating formulations—GM3E and GMB6), whereas others increased the absorption of smoke-derived compounds (Parka and wipe-out). These findings highlight that those protective treatments may have variable and sometimes counterproductive effects on smoke compound uptake.