Characterizing Glycosidically-Bound Sensory Precursors in Smoke-Exposed Vitis vinifera Berries
Matthew Noestheden, Katelyn Thiessen, and Wesley Zandberg*
*University of British Columbia Okanagan, 1177 Research Road, BC, Canada (email@example.com)
Volatile phenolic compounds like guaiacol and their glycosides influence the sen-sory attributes of wine made from smoke-exposed Vitis vinifera berries and corre-late with unpleasant “smoky,” ‘ashy,” “burnt meat,” and “Band-Aid” aromas. Un-derstanding this phenomenon is paramount because much of the North American winegrape crop is produced near forest fire-prone regions. To date there has been a lack of detailed characterization of the phenolic glycosides, with the majority putatively assigned in the absence of direct empirical evidence. However, phenolic glycosides constitute a “sensory potential” that can negatively impact the sensory profile of a wine following fermentation or after bottling. This hinders efforts to develop remedial and preventative strategies, precludes absolute quantitative assessment of the total pool of volatile phenolic compounds, and confounds any correlation between volatile phenolics and their potential impact on wines made from smoke-exposed berries. The goal of this study was to develop a comprehen-sive workflow to characterize phenolic glycosides, including their glycosidic linkages and anomeric chemistry, and to facilitate potential identification of acidic or modified glycones. Guaiacyl and syringyl glycosides were synthesized and used as model systems to develop analytical methods, as these putative glycosides represent the best (albeit incomplete) report of the observed glycosides present in smoke-exposed berries. A combination of exoglycosidase enzymes, uHPLC-MS, GC-MS, and CE-MS was used to develop and validate the analytical workflows. Method validation results for quantification of phenolic glycosides in smoke-exposed berries are shown. The developed analytical strategies can be extended to other glycosylated metabolites integral to wine quality like terpenoids or norisoprenoids, which are predominantly biosynthesized as glycosidically-linked precursors.
Funding Support: MITACS Accelerate NSERC