EFFECTIVENESS OF APPLIED MATERIALS IN REDUCING THE ABSORPTION OF SMOKE MARKER COMPOUNDS IN A SIMULATED WILDFIRE SCENARIO

Abstract

Smoke taint (ST) is a grape-wine off-flavour that may occur when grapes absorb volatile phenols (VPs) originating from wildfire smoke (1). ST is associated with the negative sensory attributes such as smoky and ashy notes. VPs are glycosylated in the plant and thus present in both free and bound forms (2; 3). Wildfire smoke has resulted in a decline in grape and wine quality and financial losses which has become a prominent issue for the global wine industry. This fact has highlighted the need to develop mitigation strategies to manage the impact of smoke exposure on grapes and the resulting wines (4). Currently there are no recommended mitigation action for grape smoke exposure.
The objective of this experiment was to compare the relative effectiveness of applying different potential protective barrier sprays to grapes in a simulated wildfire scenario. Twelve different material combina-tions were applied close to harvest as potential barrier sprays on three bunches each using four Cabernet Sauvignon vines. The vines were exposed to smoke for two hours three days after the barrier application. Control samples prior to smoke exposure was taken and smoked control (no barrier applied) grapes were sampled at different time points after exposure. For the smoke application a rectangular tent structure was built. The smoke was generated by a wood pellet smoker. Air samples were taken, and atmospheric parameters were monitored during the experiment. Grapes were analysed for free and acid-labile forms of VPs using a GC-MS and for glycosylated forms using UHPLC-qTOF MS.
Results show the presence of smoke and smoke derived compounds, however there was a strong stratifi-cation in the distribution of VPs within the structure. The heterogeneous distribution of smoke is reflected in the different concentrations of uptake of VPs in the grapes. Results from non-treated grapes indicate that glycosylation of the free volatile phenols takes place within hours, with significant increases in almost all glycosylated compounds. However, variation in smoke exposure will affect the glycosylation kinetics of VPs. The study indicated that some sprays exhibited some efficacy in reducing VPs absorption under these conditions. However, other treatments seemed to exacerbate the adsorption of VPs in grapes. In a next step, these barrier sprays will be studied further under field conditions. Acknowledgements: This work has been funded by the USDA-ARS.