Chardonnay, Merlot, and Pinot gris grapes were treated with smoke generated by the combustion of Ponderosa pine at preveraison, postveraison, and maturity. Guaiacol and 4-methylguaiaol concentrations were determined in the mature harvested grapes using a stable isotope dilution assay. Both guaiacol and 4-methylguaiacol were sorbed by the grapes during the smoke treatments and remained until the grapes were harvested. There was a general trend for increasing sorption of guaiacol and 4-methylguaiacol as grapes matured. A positive linear correlation was observed between the guaiacol:4-methylguaiacol ratio and guaiacol concentration for all smoke-treated grape samples that had concentrations above detection limits. Guaiacol concentrations ranged from 2 to 26 μg/L. These grapes could yield a wine where the concentrations exceed the detection threshold of guaiacol and the concentrations were of the same order as that resulting from contact with oak. An hour of smoke exposure would have an impact on the sensory characteristics of the resulting wines.
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