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

AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines
6.2.2 Tasting Panel
Nine tasters (five males and 4 females) were trained for this study. They were drawn from a group of
people with considerable experience in profiling wine aroma, flavour and the taste sensations of bitterness
and acidity. While some tasters were experienced in assessing the astringency of red wines, none had
previously assessed phenolic tastes in white wine.
Tasters had been previously accepted for panel membership on the basis of their general sensory acuity
including sensitivity to the bitter tasting quinine sulfate (15 mg/L) (ISO 8586). Tasters were further
screened just prior to the trial for their sensitivity to bitterness elicited by 3.2 mM 6-n-propylthiouracil
(PROP). An aqueous solution of the compound was rated for bitterness using a labeled magnitude
estimation scale. As this scale has been shown to exhibit ratio properties, the data showed that the tasters
differed around three-fold in their perception of bitterness. Despite this expected variation in bitterness
sensitivity, the initial screening using quinine sulfate suggested that all of the tasters involved in the study
were adequately able to detect bitterness.
6.2.3 Taster Training
A two hour training session was used to arrive at descriptors and definitions for the textural sensations
associated with the fractions. The training examples that were tasted and discussed were 1) a commercial
unwooded McLaren Vale Chardonnay that had been extensively stripped of its phenolics using Amberlite
FPX-66 resin (the base wine), 2) the base wine with its whole phenolics added back, and 3) the base wine
plus the whole phenolics extracted from an Adelaide Hills Chardonnay. The base wine was the same as
that used in the formal assessment of the phenolic fractions.
The attributes, astringency, bitterness, viscosity, burning, acidity (in mouth) and acidity aftertaste (AT)
were agreed upon by the tasters as adequately representing the samples presented during training. The
agreed definition of the terms is given in Appendix B, Table B-3.
6.2.4 Formal Assessment
Tastings were conducted in triplicate, one week apart. During each session, all 13 treatment combinations
including the control were presented in a randomised order to each assessor. The fractions were added to
a one year old unwooded McLaren Vale Chardonnay (the same wine used in Chapter 3) that had been
extensively stripped of its phenolics by the Amberlite FPX-66 resin. 30 mL of sample were tasted from
ISO wine tasting glasses at room temperature and under amber lighting. Tasters assessed the intensity of
astringency, bitterness, acidity, viscosity and ‘burning’ using a 15 cm partially structured line scale as
described previously. Assessors were asked to rinse their mouth with water and were required to wait two
minutes before tasting the following sample, and to rest for 15 minutes after every fourth sample. The
ballots were served to tasters by the FIZZ v 2.46 sensory data acquisition software (Biosystèmes,
Couternon).
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