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AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines 6.2.5 Analysis of Fractions The fractions were analysed using the HPLC method described in section A.3. Peak areas were used to evaluate the relative contribution of different phenolic species to the fraction. A280, A320 and A370 of the sensory samples were taken at the conclusion of each session. 6.2.6 Statistical Analysis A two way analysis of variance with assessors and fraction addition as factors was conducted by wine from which the fractions were extracted. Judges were treated as random factors. While the fractions were collected in the same way from each wine, HPLC analysis clearly indicated that they varied in at least one component. Therefore it was necessary to analyse each set of fractions collected from each of the three wines separately. A Dunnett’s test was conducted to compare the sensory effects of each fraction addition on that of the control wine. A Partial Least Squares analysis was also conducted with the sensory attributes as dependent variables and A280, A320 and A370 as dependent variables. 6.3 Results and Discussion 6.3.1 Fraction Composition The Oasis HLB resin has both hydrophilic and hydrophobic groups and as such it works in a mixed mode. As a result, few fractions contained phenolic compounds that were confined to a particular phenolic class. However, there were distinct compositional patterns; Figure 6-1 depicts the HPLC traces of each fraction while Table 6-1 gives the relative contributions of compounds classed by their A280, A320 and A370. Flow Through (FT) fractions were complex, but primarily consisted of the esterified hydroxycinnamic acids and grape reaction products. But even these differed. Notably, the fraction taken from the Gewurztraminer was distinguished by a cysteine GRP derivative not found in the other FT fractions. F1 fractions contained tyrosol and mostly free hydroxycinnamic acids, and in the case of the two Australian wines, a syringic acid like compound. The F1 fractions taken from the two Australian wines also contained quercetin-3-glucuronide. Page | 48
AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines FT F1 F2 F3 mAU 40 30 20 10 mAU 40 30 20 10 0 30 20 10 Figure 6-1 : HPLC-DAD traces of phenolic fractions separated from three commerical wines on an HLB chromatography column.Blue = A280 nm, Red = A320nm, Green = A370nm Page | 49 0 20 40 60 80 100 0 0 20 40 60 80 100 min 70 60 50 40 30 20 10 0 20 40 60 80 100 0 0 20 40 60 80 100 mAU 175 150 125 100 75 50 25 0 0 20 40 60 80 100 30 F1 F1 20 10 40 0 0 20 40 60 80 100 20 20 0 4 0 20 40 60 80 100 min 0 20 40 60 80 100 mAU 100 80 FT FT 30 F2 20 F2 F3 10 F3 60 40 20 0 80 60 10 0 20 40 60 80 100 20 40 60 80 100 0 0 20 40 60 80 100 20 40 60 80 100 Gewurztraminer Fiano Riesling hard pressings
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