Development of improved procedures for evaluating the smoke aroma potential of grapes exposed to forest fire smoke

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Ripening grapes exposed to forest fire smoke often yield wines that are characterized by an unpleasantsmoky/ashy flavor (or aroma) that is unacceptable to consumers. This phenomenon, called smoke-taint, isincreasingly problematic for Canada's vineyards and wineries since these are often located in regions prone tofrequent, intense forest fires. Given the potential for significant financial losses due to smoke-tainted wines,there is an obvious need for risk assessment strategies that can accurately determine the intensity of smokyflavor in grapes before fermentation (and, ideally, harvest). Current testing methods employ an analyticaltechnique known as gas chromatography-mass spectrometry (GC-MS) to test for the presence of compounds(like guaiacol) known to have a smoky flavor. Although several North American companies already provideGC-MS-based smoke-taint tests, a major problem with these tests is that compounds like guaiacol are oftenstored in grapes linked to various sugars. These sugar-linked, smoke-flavoured compounds are neitherdetectible by GC-MS nor are they easily perceptible by taste or smell, however, they maybe released by theyeast during fermentation and possibly ageing. Based on our knowledge of the regulation other flavourcompounds in grapes/wines, it is hypothesized that the majority of smoke-flavoured compounds are storedwithin grapes as their sugar-linked analogues. We are proposing to develop procedures by which thesugar-linked smoke-flavoured compounds in grapes can be rapidly cleaved, without fermentation, to enablecompounds like guaiacol to be detected by existing GC-MS methods. The conditions to effect such cleavagethat have been reported in the literature published to date are not suitable to be used for accurate assessmentpurposes. Our improved method will permit our company partner, Sebastian Farms (a vineyard in the MarkAnthony Group) to assess the "smoke-aroma potential" of grapes before harvest, enabling insurance planning,and supporting the development of in-vineyard or in-winery mitigation strategies. The method will be fullycompatible with Sebastian's existing smoke-taint assessment providers and R&D facilities.