INVESTIGATION OF FILM COATINGS AS A PROTECTIVE LAYER IN REDUCING THE ABSORPTION OF SMOKE PHENOLS INTO PINOT NOIR GRAPES
Wine grapes exposed to wildfire smoke have resulted in wines with burnt and ashy sensory characteristics¹, that are undesirable qualities in wine. In extreme wildfire events, this can lead to total loss of grape crop. Currently there are no effective solutions in the market to prevent the uptake of smoke compounds into grapes. In this study, previously developed innovative film coatings were tested to analyze their effectiveness in reducing smoke phenol absorption². Four different cellulose nanofiber-based film types were investigated. The film types varied in their chitosan and/or β-cyclodextrin composition. Film coatings were applied at veraison in vineyards in the Rogue Valley and Willamette Valley. The Rogue Valley experienced two smoke events during the season from wildfires in California. The grapes from Willamette Valley experience heavy smoke exposure using designed smoke cages. At harvest, half of the grapes were washed to remove the films. This was to determine if smoke phenols were blocked or bound to the film coatings. Further analysis of the interaction of smoke phenols with film coatings was done by observing any volatile phenol diffusion through the film using a custom-made polytetrafluoroethylene apparatus. Free and bound smoke phenols in grape juice were analyzed using GCMS and smoke glycosides using LCMS³. Results show some of the film coatings were effective in reducing the amount of smoke compounds absorbed into the grapes, primarily guaiacol, 4-methyl guaiacol, syringol and 4-methyl syringol. The cresol compounds were not greatly impacted. The collective results of this study show promise for film coatings as an effective preventative technique for grape smoke exposure. Optimization of the film coating formulation will lead to the reduction in smoke sensory characteristics in wine and ultimately diminish the loss of product.
Issue: OENO Macrowine 2023
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smoke, remediation, ﬁlm, phenol