Concentration of smoke marker compounds in non-smoke-exposed grapes and wine in Australia

Background and Aims An elevated concentration of several volatile phenols and their glycosides in grapes and wines is associated with exposure of grapes to forest fire smoke. Interpretation of phenol compositional data from grapes or wines, however, is complicated by the fact that traces of these compounds can be detected in non-smoke-exposed samples. Hence, the concentration of smoke marker compounds was investigated with the aim of providing a reference data set to help determine smoke exposure. Methods and Results Thirteen phenolic compounds were measured in non-smoke-exposed grape berries and unoaked wines made from 12 cultivars collected from multiple regions across Australia over four vintages. The grapes and wines contained a low concentration of several volatile phenols and their glycosides. These varied in concentration between cultivars but showed little variation between regions and vintages. The maximum concentration observed for any analyte was below 15 mu g/kg in grapes and approximately 15 mu g/L in wine. Conclusions The results for smoke marker compounds should be considered on a per-cultivar basis when determining smoke exposure. Interpretation of results for a potentially smoke-exposed sample can be achieved based on comparison with the 99th percentile values reported here. Use of the interpretation system described should be limited to determining smoke exposure and not smoke taint. Significance of the Study This study provides a comprehensive set of data that defines the upper limits of smoke marker compounds expected in Australian grapes and wines from non-smoke-exposed vineyards that can be used for determining the likelihood of smoke exposure.