Characterizing chemical influences of smoke on wine via novel application of ¹³C-labelled smoke

D. Cole Cerrato, Lindsay Garcia, Mike Penner, Elizabeth Tomasino
Oregon State University, USA

Email contact: cole.cerrato[@]oregonstate.edu

Smoke impact is an ongoing and growing issue for vintners across the globe, with the west coast U.S. and Australia being two of the largest wine industries impacted. Wine has shown to be especially sensitive to smoke exposure, often acquiring off-flavor sensory characteristics, such as “burnt rubber”, “ashy”, or other medicinal off-flavors.¹ While several studies have examined the chemical composition of smoke influences on wine, some studies disagree on what compound(s) are having the largest impact on smell and flavor.² This study is designed to do a bottom-up approach to inventory the compounds derived in smoke from a grassland-like fire that are potentially influencing wine chemical composition. Barley (Hordeum vulgare) was chosen as a fuel source for its relatively fast growth and high lignin content, a biochemical pre-cursor compound responsible for many smoke sensory attributes. Barley was grown from seed in soil media for 4-6 weeks or until achieving GS 43-44 on the Zadoks’ scale of cereal growth in ambient greenhouse conditions in Corvallis, OR. At GS the 43-44 stages in the plant life cycle, barley growth accelerates, wherein the barley was placed in a sealed translucent container.³ Ambient ¹²CO₂ was purged to <50 ppm using an air supply with only trace CO₂, followed by administration of 1000-3000 ppm ¹³CO₂ using a once a day pulsed-labelling method. The barley was incubated for five days with daily ¹³CO₂ pulses, followed by 2 days to dehumidify to prevent disease growth, and finished with another 5 days of ¹³CO₂ incubation. Chardonnay and pinot noir wine grapes, acquired from Woodhall Vineyard in Monroe, Oregon, were arranged in a sealed tent where bundles of dried ¹³C-labelled barley were burned at 5 g increments and piped “cold” to the sealed tent. 1 μm smoke density was maintained between 20-100 mg/m³ by burning 5g bundles of barley as the density approached the minima. This density was maintained for 6 hours. The smoke-affected wine was made using standard techniques to < 0° Brix, followed by bottling and cold storage. Subsequent studies examine the chemical compostion of barley using IR-MS to determine ¹³C composition and HPLC, GC-MS, and ¹³C NMR to perform a thorough chemical analysis on wine exposed to high amounts of smoke and the non-treated controls.

References:

1. Kennison, K.R.; Wilkinson, K.L.; Williams, H.G.; Smith, J.H.; and Gibberd, M.R. Smoke-derived taint in wine: Effect of post harvest smoke exposure of grapes on the chemical composition and sensory characteristics of wine. Journal of Agriculture and Food Chemistry. 2007. 55 (26), 10897-10901.
2. McKay, M.; and Buica, A. Factors influencing olfactory perception of selected off-flavour-causing compounds in red wine. South African Journal of Enology and Viticulture. 2020. 41 (1), 56-71.
3. Chang, T.T.; Konzak, C.F.; and Zadoks, J.C. A decimal code for the growth stages of cereals. Weed Research. 1974. 14, 415-421.