Detection of biomarkers for characterizing smoke-taint in grapes

In a bushfire burning of plant material generates volatile phenolics that may be absorbed by berries and leaves of grapes in nearby vineyards. In grapes these phenolics form glycoconjugates and the undesirable sensory attributes of smoke-exposed grapes only develop post-fermentation in the wine making process, when the free phenolics are released. To reduce the financial losses from producing smoke-tainted wines, phenolic glycosides associated with smoke-taint in grapes are currently monitored in analytical laboratories. Here, we performed LC-MS analysis on extracts of diverse grape varieties of various geographic sites and with varying levels of smoke taint exposure. Discovery of smoke-taint biomarkers, based on untargeted analysis led to the identification of additional phenolic compounds that could contribute significantly to the smoke-tainted flavour of wine. A total of 73 differentially expressed metabolites were detected and LCMSMS analysis resulted in the structural assignment of 15 compounds, including guaiacol and syringol derivatives and novel glycoconguate intermediaries.