Changes in Smoke-Taint Volatile-Phenol Glycosides in Wildfire Smoke-Exposed Cabernet Sauvignon Grapes throughout Winemaking

Uptake and Glycosylation of Smoke-Derived Volatile Phenols by Cabernet Sauvignon Grapes and Their Subsequent Fate during Winemaking

“…These results demonstrate the rapid uptake of volatile phenols from smoke by grapes during grapevine exposure to smoke, and as reported in previous studies [12][13][14][15][16][17][18], their subsequent in vivo glycosylation. However, while some volatile phenol glycoconjugates (measured as syringol glucose-glucoside equivalents) were observed at significantly elevated concentrations in HS grapes 24 h after smoke exposure (i.e., at t = 2), namely, syringol glucose glucoside (gentiobioside), cresol glucoside and cresol rutinoside (Table S1), accumulation of other volatile phenol glycoconjugates seemingly occurred one to four weeks after smoke exposure (i.e., between t = 3 and t = 4) (Table S1).…”

“…Of the 31 glycoconjugates measured (a mix of mono-, di-and trisaccharides), 20 decreased in concentration, five increased in concentration and six were not significantly different in concentration, from juice after pressing to wine after bottling; the largest changes in glycoconjugate concentrations were observed during the first half of primary fermentation, when glycosidase activities of Saccharomyces yeast were highest. However, it is difficult to make direct comparisons with the current study, given few glycoconjugates of guaiacol or syringol were detected, and the scope of the project was limited to analysis of glycoconjugates (i.e., no volatile phenol or sensory data were reported for finished wine) [17]. As smoke taint research has progressed over the past~15 years, the suite of volatile phenols used as smoke taint markers has evolved, with new methods for direct and indirect measurement of free and bound volatile phenols being developed.…”

“…Several studies have shown that a significant pool of volatile phenol glycoconjugates remains in wine after fermentation [5][6][7]17,19,20,27,28]. However, to date, the changes in glycoconjugate concentrations during fermentation have not been extensively studied.…”

“…To date, Caffrey and colleagues have published the only other study that measures changes in volatile phenol glycoconjugates during winemaking [17]. Of the 31 glycoconjugates measured (a mix of mono-, di-and trisaccharides), 20 decreased in concentration, five increased in concentration and six were not significantly different in concentration, from juice after pressing to wine after bottling; the largest changes in glycoconjugate concentrations were observed during the first half of primary fermentation, when glycosidase activities of Saccharomyces yeast were highest.…”

A Simple GC-MS/MS Method for Determination of Smoke Taint-Related Volatile Phenols in Grapes

“…As a result, seven VPs, including guaiacol, 4-methylguaiacol, m-cresol, p-cresol, o-cresol, syringol, and 4-methylsyringol, are currently monitored in analytical laboratories as markers for smoke taint appraisal in grapes and wines [ 3 ]. In addition, VP glycosides can be formed through conjugation with sugars once inside berry tissues and these non-volatile compounds are precursors from which free VPs could be released during vinification or wine storage [ 4 , 5 ]. Consequently, measuring glycosidically conjugated VPs is also essential for estimating the potential risk of producing smoke-tainted wines.…”