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Microvinification Versus Hydrolysis: A Comparative GC-MS/MS Study for Predicting Smoke Taint Severity in Winegrapes

Ezekiel R. Warren, Misha T. Kwasniewski
Am J Enol Vitic.  2026  77: 0770011  ; DOI: 10.5344/ajev.2026.25028

Article Figures & Data

Figures

  • Six line graphs compare guaiacol and m-cresol values across four treatments for three grape cultivars. The six line graphs are arranged in 2 rows and 3 columns. The column headings from left to right are Cabernet franc, Cabernet Sauvignon, and Petit Verdot. Panel A shows the solid circle line rising from Juice to a peak at Acid, then decreasing through Enzyme and M V, while the dashed triangle line remains lower and rises slightly from Juice to Acid and Enzyme before decreasing at M V. Panel B shows both lines rising from Juice to Acid, staying close at Enzyme, and decreasing slightly at M V. Panel C shows both lines rising from Juice to Acid, staying close at Enzyme, and ending slightly higher at M V for the solid circle line. Panel D shows the solid circle line rising sharply from Juice to Acid, then decreasing through Enzyme and M V, while the triangle dashed line rises from Juice to Acid, remains near Enzyme, and decreases slightly at M V. Panel E shows the solid circle line rising from Juice to Acid, staying level at Enzyme, and decreasing at M V, while the triangle dashed line rises from Juice to Acid and decreases through Enzyme and M V. Panel F shows both lines rising from Juice to Acid, dipping slightly at Enzyme, and ending with the solid circle line above the triangle dashed line at M V. All values are approximated.
    Figure 1

    Mean concentration (ng/mL) of guaiacol and m-cresol in Cabernet franc, Cabernet Sauvignon, and Petit Verdot. Samples are untreated juice (Juice), juice after acid hydrolysis (Acid), juice after enzymatic hydrolysis (Enzyme), and juice after microvinification (MV) for grape samples from two different vineyards. The horizontal dotted lines at 84.38 ng/mL (A to C) and 47.76 ng/mL (D to E) indicate the concentration observed in a severely smoke-affected Cabernet Sauvignon wine (Oberholster et al. 2023). The horizontal dashed lines at 23 ng/mL (A to C) and 20 ng/mL (D to F) indicate the aroma thresholds of guaiacol and m-cresol, respectively (Parker et al. 2012). Each field sample was divided into four separate aliquots with each digested separately using each method (n = 4 [replicates per individual treatment]; 16 individual values if including all samples within vineyard and cultivar), with all samples analyzed in triplicate. Error bars indicate standard deviation of biological replicates.

  • A bar graph compares mean C V values for 7 volatile compounds across Juice, Acid, Enzyme, and M V treatments. The bar graph shows mean C V percent values for volatile compounds across 4 treatments. The vertical axis is labeled Mean C V percent and ranges from negative 20 to 140. The horizontal axis is labeled Volatile compound and lists Guaiacol, 4-Methylguaiacol, o-Cresol, 4-Ethylguaiacol, p-Cresol, m-Cresol, and Eugenol. A legend in the upper right lists Juice, Acid, Enzyme, and M V. For Guaiacol, Acid has the tallest bar near 78, followed by Juice near 10, M V near 9, and Enzyme near 6. For 4-Methylguaiacol, Enzyme is tallest near 26, followed by Acid near 20, M V near 6, and Juice near 3. For o-Cresol, Acid is tallest near 111, followed by Juice near 10, M V near 10, and Enzyme near 7. For 4-Ethylguaiacol, Acid is tallest near 42, followed by M V near 11, Enzyme near 10, and Juice near 0. For p-Cresol, Enzyme is tallest near 17, followed by M V near 16, Acid near 8, and Juice near 5. For m-Cresol, Acid is tallest near 28, followed by Enzyme near 18, M V near 16, and Juice near 10. For Eugenol, Acid is tallest near 46, followed by M V near 4, Juice near 3, and Enzyme near 3. All values are approximated.
    Figure 2

    Average coefficient of variation (CV) of each extraction method for volatile compounds in juice (Juice), acid hydrolysis (Acid), enzyme hydrolysis (Enzyme), and microvinification (MV) (n = 6 cultivars, each with four replicates for the CV). Error bars indicate standard error of the CV within the treatment.

Tables

  • Table 1

    Two-way analysis of variance of extraction method, cultivar, and interaction for smoke-related volatile compounds (α = 0.05). Df, degree of freedom.

    Method
    Pr (>F)    		Cultivar
    Pr (>F)    		Method:Cultivar
    Pr (>F)    		Residual
    Df251054
    Guaiacol0.01625*a6.60e × 10−16***0.15019ndb
    4-Methylguaiacol2.20e × 10−16***9.62e × 10−08***2.50e × 10−09***nd
    4-Ethylguaiacol1.27e × 10−13***0.000592***2.03e × 10−05***nd
    o-Cresol0.24450.35230.5448nd
    p-Cresol2.20e × 10−16***6.48e × 10−08***3.91e × 10−05***nd
    m-Cresol0.001306**1.19e × 10−05***0.014786nd
    Eugenol1.84e × 10−14***0.001293**6.33e × 10−05***nd

    • ↵a*, **, and *** indicate statistically significant differences at p = 0.01, 0.001, and 0, respectively.

    • ↵bnd, not determined.

  • Table 2

    Mean volatile phenol compound concentration of each method and cultivar. CF, Cabernet franc; CS, Cabernet Sauvignon; PV, Petit Verdot.

    WineMethodGuaiacol
    (ng/mL)    		4-Methyl guaiacol
    (ng/mL)    		4-Ethyl guaiacol
    (ng/mL)    		o-Cresol
    (ng/mL)    		p-Cresol
    (ng/mL)    		m-Cresol
    (ng/mL)    		Eugenol
    (ng/mL)
    CF1Juice16.0 ± 1.4a4.5 ± 0.32.4 ± 0.05.5 ± 1.70.8 ± 1.23.1 ± 0.26.9 ± 0.4
    Acid125.0 ± 10418.5 ± 4.957.6 ± 32.641.5 ± 33.11153.2 ± 284.758.3 ± 37.295.4 ± 67.7
    Enzyme142.5 ± 7.916.1 ± 0.92.8 ± 0.334.6 ± 2.5206.6 ± 18.331.7 ± 2.58.1 ± 0.1
    Microvinification78.6 ± 6.78.3 ± 0.91.4 ± 0.219.7 ± 2.3137.0 ± 32.020.5 ± 4.45.0 ± 0.2
    CF2Juice22.3 ± 1.14.7 ± 0.12.4 ± 0.05.1 ± 0.30.7 ± 1.52.8 ± 0.46.9 ± 0.1
    Acid74.8 ± 59.714.0 ± 2.919.4 ± 4.612.4 ± 12.0952.5 ± 118.622.1 ± 3.5130.5 ± 28.8
    Enzyme138.3 ± 6.414.2 ± 0.32.7 ± 0.432.3 ± 1.9148.8 ± 8.623.7 ± 1.28.2 ± 0.1
    Microvinification55.7 ± 3.56.2 ± 0.31.5 ± 0.214.5 ± 1.090.2 ± 7.717.6 ± 1.44.9 ± 0.2
    CS1Juice13.3 ± 0.73.4 ± 0.22.4 ± 0.06.3 ± 0.40..0 ± 0.02.3 ± 0.26.6 ± 0.0
    Acid6.8 ± 7.018.3 ± 4.3126.3 ± 79.3300.1 ± 539.51077.0 ± 173.229.4 ± 9.186.4 ± 41.4
    Enzyme70.3 ± 4.15.8 ± 0.12.6 ± 0.042.5 ± 2.8164.0 ± 8.130.0 ± 3.8.06.8 ± 0.1
    Microvinification62.1 ± 6.63.6 ± 0.11.3 ± 0.129.3 ± 3.253.0 ± 11.421.6 ± 1.83.6 ± 0.1
    CS2Juice1.5 ± 0.53.3 ± 0.02.4 ± 0.02.9 ± 0.20.0 ± 0.02.1 ± 0.46.6 ± 0.0
    Acid21.4 ± 17.315.6 ± 3.134.8 ± 8.47.3 ± 6.0692.3 ± 112.918.5 ± 3.945.3 ± 44.6
    Enzyme30.6 ± 2.03.8 ± 0.72.4 ± 0.121.8 ± 1.589.9 ± 9.514.9 ± 2.26.7 ± 0.1
    Microvinification26.9 ± 3.42.5 ± 0.11.2 ± 0.012.5 ± 1.928.1 ± 5.17.4 ± 2.93.5 ± 0.1
    PV1Juice75.3 ± 1.66.5 ± 0.12.4 ± 0.08.3 ± 0.67.6 ± 2.44.0 ± 0.26.8 ± 0.3
    Acid242.5 ± 134.015.2 ± 3.220.1 ± 11.612.4 ± 8.8654.7 ± 54.721.7 ± 2.224.7 ± 1.2
    Enzyme229.6 ± 18.28.4 ± 5.43.4 ± 0.726 ± 2.682.1 ± 3.220.7 ± 7.67.8 ± 0.8
    Microvinification253.4 ± 22.316.0 ± 1.32.7 ± 0.227.1 ± 1.7132.4 ± 14.426.6 ± 2.16.8 ± 0.5
    PV2Juice60.7 ± 1.45.2 ± 0.12.4 ± 0.04.8 ± 0.30.0 ± 0.02.3 ± 0.26.9 ± 0.4
    Acid119.3 ± 75.518 ± 2.182.5 ± 18.8114.3 ± 181.9714.0 ± 164.525.2 ± 6.926.7 ± 8.8
    Enzyme215.2 ± 11.25.3 ± 3.42.5 ± 0.319.5 ± 0.840.4 ± 3.916.3 ± 5.58.3 ± 0.2
    Microvinification184.4 ± 13.99.6 ± 0.91.6 ± 0.317.2 ± 1.339.5 ± 6.116.2 ± 1.95.7 ± 0.4

    • ↵aValues are means ± standard deviation of n = 3 independent treatment preparations per biological sample; two biological samples per cultivar are shown separately (e.g., CF1, CF2).

Additional Files

  • Supplemental Table 1  Basic fruit chemistry of grapes used in this study. Values represent a single measurement for each trait. TSS, total soluble solids; TA, titratable acidity.

    Supplemental Table 2  Gas chromatography-tandem mass spectrometry (GC-MS/MS) standards and multiple reaction monitoring (MRM) transitions.
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Microvinification Versus Hydrolysis: A Comparative GC-MS/MS Study for Predicting Smoke Taint Severity in Winegrapes
Ezekiel R. Warren, Misha T. Kwasniewski
Am J Enol Vitic.  2026  77: 0770011  ; DOI: 10.5344/ajev.2026.25028
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