Evaluation of Kaolin and Bentonite Adsorptive Sprays to Reduce Uptake of Smoke-Related Compounds during Smoke Exposure Events
Thomas S Collins*, Raef Pederson, and Mackenzie
Aragon
*Viticulture and Enology Program, Washington State University,
359 University Drive, Richland, WA 99354 (tom.collins@wsu.edu)
Kaolin or bentonite-based adsorptive sprays were applied prior to deliberate smoke exposures in portable hoop-houses over four growing seasons (2018 to 2021) to evaluate their ability to reduce uptake of smoke-related compounds. Sprays (0.5 lb/ gallon) were applied to clusters and surrounding leaves to the point of run-off using hand-held or backpack sprayers the day prior to exposure. The sprayed vines and unsprayed controls were exposed to fresh smoke from burning either rangeland plant material for 48 hrs (2018) or hardwood pellets for 36 hrs (2019 to 2021). Sprayed and unsprayed controls were also prepared for the unsmoked control hoop-houses. At normal maturity, berry extracts were prepared from smoke-exposed and control fruit (2018 and 2019) or bucket-scale fermentations were done (2020 and 2021). In 2018, there was little difference in smoke marker content among treatments. In 2019, control and treated berries were wiped clean prior to preparing extracts. The resulting extracts from kaolin- or bentonite-sprayed berries had significantly less guaiacol and 4-methyl guaiacol than extracts from unsprayed smoked berries, suggesting that removal of the sprayed materials would be necessary prior to making wine from the sprayed fruit. In 2020, all treatments were exposed to smoke from actual wildfires in addition to the smoke from the deliberate exposures, confounding the results for that year. In 2021, the number of treated vines per hoop-house was increased and half of the vines were sprayed with water seven days post-exposure to remove the kaolin or bentonite spray materials. The wines made from the rinsed fruit contained significantly lower concentrations of smoke-related marker compounds than wines made from fruit that had not been rinsed after exposure, confirming the expectation that using kaolin- or bentonite-based barrier adsorptive sprays will require their removal prior to fermentation to avoid release of the adsorbed smoke compounds into the fermentation.
Funding for this project: Washington State Wine and Grape Research Program and the M.J. Murdock Charitable Trust Partners in Science
