Investigation of cellulose nanofiber-based films used as a protective layer to reduce absorption of smoke phenols into wine grapes
Volatile phenols from wildfire smoke are absorbed by wine grapes, resulting in undesirable smoky and ashy sensory attributes in the affected wine. Unfortunately the severity of wildfires is increasing, particularly when grapes are ripening on the vine. The unwanted flavors of the wine prompted a need for solutions to prevent the uptake of smoke compounds into wine grapes. Films using cellulose nanofibers as the coating forming matrix were developed as an innovative means to prevent smoke phenols from entering Pinot noir grapes. Different film formulations were tested by incorporating low methoxy pectin or chitosan. The three different coating treatments were sprayed on Pinot noir grapes from Woodhall III Vineyards in Monroe, Oregon. just prior to veraison. Smoke was applied to the grapes by burning Oregon forest duff in grills attached to specially designed greenhouse tents, which were used to contain smoke around the grape vines for six hours. Smoke density was maintained between 20 to 100 mg/m3 for smoke particles <1 μm. Film-treated grapes and controls were harvested a week after smoke exposure. Prior to winemaking, half of the coated grapes were washed and the other half unwashed, to determine if the films would contribute smoke compounds during fermentation. Grape juice and final wines were analyzed for free and bound smoke phenols[2,3]. New markers for smoke exposure, thiophenols, were also analyzed given their contribution to the ashy flavor in smoke impacted wines. The films used in this study prevented the incorporation of a wide range of smoke phenols in the subsequent wine compared to the controls. But unfortunately, did not impact all the smoke compounds. While additional work is needed, these films are prospective deterrents to grape smoke exposure during wildfire events.
Acknowledgements: Funded by USDA-NIFA-SCRI Award #2021-51181-35862 and USDA-ARS #2072-21000—057-00D.
1) Parker M. et al. (2012) Contribution of several volatile phenols and their glycoconjugates to smoke-related sensory properties of red wine. J. Agric. Food Chem., 60: 2629-2637, DOI 10.1021/jf2040548
2) Liu Z. et al. (2020) A simple GC-MS/MS method for determination of smoke taint-related volatile phenols in grapes. Metabolites, 10: 294, DOI 10.3390/metabo10070294
3) Caffrey, A., et al. (2019). Changes in smoke-taint volatile-phenol glycosides in wildfire smoke-exposed Cabernet Sauvignon grapes throughout winemaking. American Journal of Enology and Viticulture, 70(4), 373-381.
Issue: ICGWS 2023
1Dept. of Food Science and Technology, Oregon State University, Corvallis, OR, USA
2Dept. Of Horticulture Southern Oregon Research and Extension Center, Oregon State University, Central Point, OR, USA
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thiophenols, guaiacol, chitosan, pectin, coating