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

AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines
they called ‘phenolic hotness’ that they described as being a burning sensation at the back of the
throat that was unrelated to the whole mouth sensation of alcohol warmth. Informal tastings of
phenolic wines stripped of most of their alcohol under vacuum by an experienced panel supported the
existence of a back of the throat burning sensation. In the absence of a known chemical standard for
this attribute, a fresh Australian extra virgin olive oil that was described by judges at the 2010
Australian National Extra Virgin Olive Oil Show as being pungent was presented as a training
example. Pungency is an officially recognised term used by olive oil assessors to describe the throat
burning sensation elicited by the olive oil phenolic oleocanthal. The sensation was thought to be a
good proxy to illustrate a burning character as it was of known phenolic origin. Aqueous solutions of
0.5 g/L aluminium potassium sulfate, quinine sulfate (15 mg/L) and carboxymethycellulose (3 g/L)
were also presented to demonstrate astringency, bitterness and viscosity respectively.
Two or three examples of model wines (pH 3.5, 10% v/v alcohol) containing either high (60 mg/L) or
low (30 mg/L) concentrations of Grape reaction product (GRP) and caftaric acid or their mixtures,
were presented over the following three training sessions in order to generate and define taste and
texture attributes associated with the samples. The final two training sessions were used to familiarise
the tasters with the use of the 15 cm partially structured tasting scale and to identify any attribute
redundancies. Four samples (model wine, high and low GRP and high caftaric acid) were presented in
duplicate over consecutive days for this purpose.
7.2.4 Formal Assessment
The test samples were assessed in triplicate. The fifteen test samples were presented over three
sessions in a randomised order. 40 mL of sample was presented in black tasting glasses at room
temperature (23°C ±1°C). A two minute rest was enforced between samples, and an additional eight
minute rest was enforced after the third sample. The list of selected attributes and their definitions are
provided in Appendix B, Table B-3. The intensity of these was assessed using the 15 cm partially
structured line scale described previously.
7.2.5 Statistical Analysis
Where zero ratings for a particular attribute were given to all samples on all tasting occasions by an
assessor, their ratings were excluded from analysis as they were considered either insensitive to the
attribute or did not understand it. The ratings from one assessor were excluded for both the
‘astringency’ and ‘metallic’ attributes, two were excluded for ‘oiliness’, and three for the ‘prickly’
character. The ratings from at least eight assessors remained for each attribute which is considered
acceptable for descriptive analysis. Assessor consistency across tasting sessions was assessed using
Kendall’s coefficient of concordance (Siegel 1956). A three way analysis of variance of each tasting
attribute was conducted with assessors, caftaric acid concentration and GRP concentration as
treatment effects, with assessors being treated as random effects. Means separation was conducted
using Fishers Least Significant Difference. The relationship between attributes was also investigated
using Pearson’s correlation coefficients.
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