Quantitating Organoleptic Volatile Phenols in Smoke-Exposed Vitis vinifera Berries

Abstract

Accurate methods for quantitating volatile phenols (i.e., guaiacol, syringol, 4-ethylphenol, etc.) in smoke-exposed Vitis vinifera berries prior to fermentation are needed to predict the likelihood of perceptible smoke taint following vinification. Reported here is a complete, cross-validated analytical workflow to accurately quantitate free and glycosidically bound volatile phenols in smoke-exposed berries using liquid-liquid extraction, acid-mediated hydrolysis, and gas chromatography-tandem mass spectrometry. The reported workflow addresses critical gaps in existing methods for volatile phenols that impact quantitative accuracy, most notably the effect of injection port temperature and the variability in acid-mediated hydrolytic procedures currently used. Addressing these deficiencies will help the wine industry make accurate, informed decisions when producing wines from smoke-exposed berries.

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

“…These results were consistent with: 4-methylguaiacol and 4-methylsyringol being the least abundant volatile phenols in HS grapes, especially in free form at t = 1 ( Table 1) and in glycosylated forms at t = 4 ( Table 1 and Table S1); and guaiacol, cresols and syringol being the most abundant volatile phenols, in both free and glycosylated forms ( Table 1 and Table S1). Several previous studies employed enzyme, acid and/or base hydrolysis of grape homogenate, juice or wine to facilitate quantification of glycoconjugate forms of volatile phenols [1,15,[19][20][21]24,26]. Noestheden and colleagues optimized a method for measuring glycosidically-bound volatile phenols in smoke-exposed grapes using acid-mediated hydrolysis [15], key recommendations being the use of Strata X solid phase extraction (SPE) cartridges for isolation of glycoconjugates and PTFE tubes for acid digestion (instead of borosilicate glass vials, which seem to interfere with the assay yielding low recoveries for some volatile phenols).…”

Classification of Smoke Contaminated Cabernet Sauvignon Berries and Leaves Based on Chemical Fingerprinting and Machine Learning Algorithms

“…However, it is interesting that the low smoke treatment (LS) had lower g s than the high smoke with misting treatment (HSM), which indicates that misting may have reduced the effect of smoke exposure on g s . During a bushfire, the type of fuel burnt will vary depending on the region and the type of plant species native to the area, as well as the amount of smoke exposure due to land topography and wind vectors; therefore, the effect on g s may vary [ 17 , 18 , 23 , 66 ]. While misting only partially prevented the uptake of volatile phenols and glycoconjugates in grapes [ 60 ], it did appear to have a physiological effect.…”

“…Grapevine smoke exposure, and the resulting smoke taint in wine, have caused significant financial losses for grape growers and winemakers due to discarded grapes and unsaleable wine. For example, the 2009 Black Saturday bushfires in Victoria, Australia, were estimated to have caused AUD 300 million in lost revenue [ 16 , 17 , 18 , 19 ]. More recently, the Australian Grape and Wine Incorporated (AWGI) estimated an AUD 40 million loss from the 2019/2020 summer bushfires [ 20 ].…”

Removal of Volatile Phenols From Wine Using Crosslinked Cyclodextrin Polymers

“…The warmer, drier weather conditions also increase the risk of bushfires occurring near wine regions, which can lead to vineyard exposure to bushfire smoke, and another volatile phenol related off-odor, commonly known as smoke taint [5,6]. Elevated concentrations of guaiacol, 4-methylguaiacol, o-, mand p-cresol, and syringol have been found in wines made from smoke-exposed grapes [7,8], along with objectionable smoke-related sensory characters that negatively affect wine quality [8,9]. spectrometry (GC-MS) was employed to quantify changes in volatile phenol concentrations without interference between CD additives and internal standards [35].…”