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

AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines
Figure 8-18 (individual varieties in Figure 8-19) gives the mean sensory attribute ratings of the 2011
wines by treatment and variety, and Table 8-4 the significance of treatment effects. Significant effects
were seen for astringency, viscosity (including when adjusted for pH effects) and bitterness. There was
also weak evidence for winemaking treatment on metallic and oiliness. However, the effect of
winemaking on the wines taste properties was strongly dependent on variety. When averaged across
varieties, skin maceration resulted in the highest astringency and bitterness, while maceration produced
the lowest intensity of both these attributes. These results were despite these two treatments having the
same high A280, suggesting that the wines had equivalent total phenolic content (Figure 8-6). Therefore
either the differences in the respective wine matrices are affecting perception, or the differences are due to
variations in phenolic profile. The high overall average bitterness of the low phenolic hyperoxidised free
run wines is also noteworthy as higher bitterness is normally associated with higher phenolics.
The solids ferment wines consistently displayed higher level of metallic character across the three
varieties, and were on average one of the most oily, hot and burning of the treatments. With the exception
of an early study by Singleton et al. (1975), the textural properties of wine resulting from the relatively
common practice of fermenting juice containing grape solids has been not been reported. The early work
found that fermenting turbid juices did not cause an increase in total wine phenolics, but it did result in
consistently more bitter and astringent wines. We found that solids fermentation impacted on total
phenolics, total hydroxycinnamates and flavanoid extract, but the effect was variety dependent. Higher
solids resulted in higher flavanoid extract in all three varieties compared with the free run wines. The total
phenolics were the same for the Riesling and Viognier wines, but the Chardonnay wines fermented on
solids had nearly twice the total phenolics as did the free run wines. The presence of grape particles in a
must could provide a source of compartmentalised phenolics that are liberated during alcoholic
fermentation. This may explain the unique textures displayed by the solids wines in this trial.
85
Intensity
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
All Wines
Astringency Viscosity Hotness Bitter Metallic Oily Burning AT
HOX-FR WBP HOX-HP FR SOL HP MAC SKI
Figure 8-18: Mean intensity ratings of attributes associated with ‘phenolic taste’in 2011 wines. All
wines. Treatments ordered from lowest to highest in average A280. Bars show 10% LSD.