Contribution of Several Volatile Phenols and Their Glycoconjugates to Smoke-Related Sensory Properties of Red Wine

Abstract

Guaiacol and 4-methylguaiacol are well-known as contributors to the flavor of wines made from smoke-affected grapes, but there are other volatile phenols commonly found in smoke from forest fires that are also potentially important. The relationships between the concentration of a range of volatile phenols and their glycoconjugates with the sensory characteristics of wines and model wines were investigated. Modeling of the attribute ratings from a sensory descriptive analysis of smoke-affected wines with their chemical composition indicated the concentrations of guaiacol, o-cresol, m-cresol, and p-cresol were related to smoky attributes. The best-estimate odor thresholds of these compounds were determined in red wine, together with the flavor threshold of guaiacol. Guaiacol β-D-glucoside and m-cresol β-D-glucoside in model wine were found to give rise to a smoky/ashy flavor in-mouth, and the respective free volatiles were released. The study indicated that a combination of volatile phenols and their glycosides produces an undesirable smoke flavor in affected wines. The observation of flavor generation from nonvolatile glycoconjugates in-mouth has potentially important implications.

The Impact of Smoke From Vegetation Fires on Sensory Characteristics of Cabernet Sauvignon Wines Made From Affected Grapes

“…Sensory studies by Parker et al (2012) describe an ash-like aftertaste from the presence of particularly guaiacol, 4-EG, m-cresol and their glycosidic forms when tasted in model wine. The same studies further showed that even below odour-threshold levels, these compounds led to this ashy flavour, suggesting an in-mouth release of bound phenol glycosides.…”

“…Guaiacol and 4-methylguaiacol (4-MG) have been used as key indicators of smoke exposure and potential taint formation (Kennison et al, 2007;Sheppard et al, 2009). More recently, studies have demonstrated that additional volatile phenolic compounds (cresols, phenols and syringols) may account for taint characteristics in smokeaffected wines (Kelly et al, 2012;2014;Parker et al, 2012). Sheppard et al (2009) reported that methoxyphenols (including guaiacol and 4-MG) arise from the partial pyrolysis of lignin and are key contributors to the aroma of wood smoke.…”

“…Once VPs are taken up by grapes, they are rapidly metabolised into their more stable glycosidic forms (Hayasaka et al, 2010;Singh et al, 2011;Parker et al, 2012). These glycoconjugated precursors may hydrolyse during the fermentation, ageing and storage of wine to release free volatile phenols (Kennison et al, 2008;Hayasaka et al, 2013).…”

“…These glycoconjugated precursors may hydrolyse during the fermentation, ageing and storage of wine to release free volatile phenols (Kennison et al, 2008;Hayasaka et al, 2013). Parker et al (2012) also noted increases of 15 to 20 μg/L of volatile phenols released from glycosylated precursors in the mouth during tasting. This release may be enough to increase VP levels above odour-detection thresholds, which may explain the findings by Panzeri (2013) and Van Zyl (2013), namely that wines displayed 'burnt rubber' characteristics on tasting, despite VPs being present at levels below their odour thresholds.…”

Aroma Compounds responsible for the "spicy/4VG" character of sake submitted to Sake Contests

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