373 Am. J. Enol. Vitic. 70:4 (2019) 1 Department of Viticulture and Enology, University of California, Davis, CA; 2 Food Safety and Measurement Facility, University of California, Davis, CA; and 3 Agilent Technologies, Inc., Wilmington, DE 19898. *Corresponding author (seebeler@ucdavis.edu) Acknowledgments: We acknowledge the American Vineyard Foundation for fnancial support of this work. Supplemental data is freely available with the online version of this article at www.ajevonline.org. Manuscript submitted Dec 2018, April 2019, accepted May 2019 Copyright © 2019 by the American Society for Enology and Viticulture. All rights reserved. By downloading and/or receiving this article, you agree to the Disclaimer of Warranties and Liability. The full statement of the Disclaimers is available at http://www.ajevonline.org/content/proprietary-rights-notice-ajev-online. If you do not agree to the Disclaimers, do not download and/or accept this article. doi: 10.5344/ajev.2019.19001 Changes in Smoke-Taint Volatile-Phenol Glycosides in Wildfre Smoke-Exposed Cabernet Sauvignon Grapes throughout Winemaking Andrew Cafrey, 1,2 Larry Lerno, 1,2 Arran Rumbaugh, 1 Raul Girardello, 1 Jerry Zweigenbaum, 3 Anita Oberholster, 1 and Susan E. Ebeler 1,2 * Abstract: When grapes are exposed to wildfre smoke, several smoke-related aroma compounds can be transferred to the berries and become glycosylated. Although the compounds do not contribute to grape aroma in the glycosyl- ated form, the free volatile phenols can be released throughout winemaking and wine aging to produce undesirable “smoke tainted” wines. Measurement of the intact glycosides provides insight on the potential favor of a wine and provides information on the efect of winemaking practices on release of volatile aroma compounds from glycosidic precursors. Smoke taint-associated volatile-phenol glycosides in Vitis vinifera cv. Cabernet Sauvignon grape berries were tentatively identifed and semi-quantitated using a comprehensive database coupled with ultra-high performance liquid chromatography and accurate-mass time-of-fight tandem mass spectrometry. Eight trisaccharide volatile- phenol glycosides were tentatively identifed for the frst time in grapes. The method developed here was applied to monitor changes associated with smoke exposure in 31 volatile-phenol glycosides during winemaking. The most hydrolytic time period during the winemaking process was the frst half of fermentation with Saccharomyces yeast (EC-1118), after which there was little efect on the phenolic glycosidic profle of fermenting wines. This is the frst report to monitor changes of these 31 phenolic glycosides during winemaking using direct measurement of the gly- cosides. The information can be used to improve knowledge of the changes in smoke-taint glycosides and release of phenolic compounds that afect sensory properties of smoke-afected grapes and wines. Key words: Cabernet Sauvignon, fermentation, glycosides, smoke taint, ultra-high performance liquid chromatography high resolution tandem mass spectrometry, volatile phenols As fres near grapegrowing regions increase in frequency, there is a need to understand how smoke exposure afects the fruit of Vitis vinifera, particularly the incidence of undesir- able “smoke taint” aromas in the fnished wines. The sensory characteristics of smoke taint have been well studied to date and are described as orthonasal aromas such as smoky, dirty, band-aid, earthy, medicinal, burnt/charred, muddy, tarry, smoked meat, or ashtray, along with ashtray-like retronasal aromas (Kennison et al. 2007, Ristic et al. 2011, Parker et al. 2012, Mayr et al. 2014). A class of molecules called volatile phenols have been shown to contribute to these ortho- and retro-nasal aromas in the wine. These aromas can be imparted into the grape berries in as little as half an hour of smoke exposure under intense experimental applications of smoke from burning straw (Kennison et al. 2008, Hayasaka et al. 2010a). Upon smoke exposure, free volatile phenols distrib- ute themselves evenly throughout the pericarp of the berry (Hayasaka et al. 2010b, Dungey et al. 2011). Guaiacol and 4-methylguaiacol are the most well-known markers of smoke taint. However, a search of the literature shows that several other volatile phenols should be consid- ered, including, but not limited to, phenol, cresol, 4-ethylphe- nol, 4-ethylguaiacol, syringol, 4-methylsyringol, and eugenol (Kennison et al. 2007, 2008, Ristic et al. 2011, Hayasaka et al 2013, Noestheden et al. 2018). During smoke exposure, vola- tile phenols are absorbed into the grape tissue and glycosyl- ated as a form of storage and detoxi fcation. As a result, the volatile phenols are largely immobilized in the grape tissue (Hayasaka et al. 2010a) as monoglucosides, pentosylgluco- sides, gentiobiosides, and rutinosides (Hayasaka et al. 2013). In fnished wines, the abundance of each volatile phenol is proportional to the duration and amount of smoke exposure on the grapes, as well as the timing of smoke exposure during grape growth. Previous studies have shown that even a single exposure to smoke starting three to 24 days postveraison can impart a signifcant amount of volatile phenols into the berries (Kennison et al. 2009). Most studies utilize the same glycosylation motifs for vola- tile phenols that have been observed for other volatiles, such as monoterpene alcohols and norisoprenoids. Much of the