Abstract
Volatile phenols (VPs) derived from smoke-exposed grapes are known to confer a smoky flavor to wine. Current methods for determination of VPs in grape berries either involve complex sample purification/derivatization steps or employ two analytical platforms for free and bound VP fractions. We report here a simple gas chromatography-tandem mass spectrometry (GC-MS/MS) method for quantification of both free and bound VPs in grapes, based on optimized (1) GC-MS/MS parameters, (2) an analyte extraction procedure, and (3) phenol glycoside hydrolysis conditions. Requiring neither sample cleanup nor a derivatization step, this method is sensitive (LOD ≤ 1 ng/g berries) and reproducible (RSD < 12% for repeated analyses) and is expected to significantly reduce the sample turnover time for smoke taint detection in vineyards.
Highlights
Wildfires and controlled burns generate smoke particulates that could be taken up by the berries and leaves of grapes in nearby vineyards
Wines made from smoke-exposed grapes can present undesirable sensory attributes known as smoky or smoke tainted with reduced palatability and market acceptance [1]
The high specificity of the multiple reaction monitoring (MRM) scan allowed a limit of detection (LOD) ≤ 1 ng/mL and limit of quantification (LOQ) between 1 and 3.3 ng/mL to be achieved for all 16 volatile phenols (VPs)
Summary
Wildfires and controlled burns generate smoke particulates that could be taken up by the berries and leaves of grapes in nearby vineyards. Wines made from smoke-exposed grapes can present undesirable sensory attributes known as smoky or smoke tainted with reduced palatability and market acceptance [1]. While the chemical composition of smoke from wood pyrolysis is rather complex, volatile phenols (VPs) are believed to be the major aroma compounds that confer the smoke taint characteristics to grapes and wines [1,2,3]. Guaiacol and 4-methylguaiacol were the first recognized VPs in relation to smoke taint [1,4]. 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]. VP glycosides can be formed through conjugation with sugars once inside berry tissues and these non-volatile compounds are precursors from which free
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