Identification of the major drivers of 'phenolic' taste in ... - GWRDC

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AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines 4.4 Results and Discussion 4.4.1 Study 1: Effect on ‘Pinot G’ Style The PLS regression coefficients standardised for differences in scale are given in Figure 4-1. While viscosity and oiliness were mostly associated with residual sugar, oiliness was further associated with ethanol concentration. Palate hotness and bitterness were mostly determined by the level of ethanol. Consistent with these results, Gawel et al. (2007) found that higher alcohol concentration increased the viscosity of two of the three wines studied, and increased the perceived hotness of all three. The result that bitterness was associated with alcohol content contradicted the results of a model study using whole phenolic extracts from Riesling (Chapter 6), but was consistent with other model studies (Fontoin et al. 2008; Fischer and Noble 1994). Wines that were lower in titratable acidity (TA) tended to be less astringent, viscous, oily, hot and bitter. Astringency in these wines was mostly associated with lower pH and also lower TA. pH and TA are usually moderately negatively correlated in grapes and wine. However under combination of low effects could be attributable to a situation where a wine went through either partial or no malolactic fermentation. The PLS regression analysis also suggesed that wine phenolics (measured by A280 and A320) contributed much less to astringency, viscosity, oiliness, hotness and bitterness than the major compositional variables that reflect the wine matrix (pH, TA, residual sugar and alcohol). However, best subset regression suggested that the minimum number of analytical features required to best describe astringency and oiliness should also include A280 and A320 respectively (Table 4-1). The conclusions drawn from the two analyses are largely consistent as the PLS analysis revealed that absorbance at 280 and 320 nm were the most important phenolic indices in explaining astringency and oiliness respectively. Conformance to a particular style implies that the wine has characteristics that, on the whole, can be recognised as being from a particular variety and have been made using specific wine-making processes (Cadot et al. 2010; Maitre et al. 2010). Conformance to defined styles has commercial importance as it provides consumers with the confidence to repeatedly purchase that wine, or seek other wines that are alike. Both PLS and best subset regression suggested that Pinot Gris style could be differentiated from Pinot Grigio style on the basis of the combined effects of total phenolics (A280), ethanol and residual sugar. Of note was the influence of total phenolics on style. While it was not a strong determinant of any particular sensory attribute, it was identified as being one of the most important determinants of the ‘Gris’ vs.‘Grigio’ style. Page | 34
AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines PLS Coefficient Page | 35 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 Astringency (0.056) Viscous (0.002) Oily (
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