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

AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines
keep back pressure under 300 bar and reduce the flow rate to 0.13 mL/min during the high methanol
phase. With two in series the time taken to elute all peaks has now increased to just over 100 minutes.
To ensure post-run column equilibration was attained, a wait time of 20 minutes was incorporated into
the method program, meaning that a complete run lasts 155 minutes (Figure A-1). Using two columns
increased the resolution by a factor of two and allowed caffeic acid and one of the coutaric acid
isomers to be separated. This improvement in resolution also allows the separation of 2-S-glutathionyl
adduct of trans-caftaric acid (GRP) from the free acid. These are depicted Figure A-2. Unfortunately
the resolution between quercetin-3-O-glucoside and quercetin-3-O-glucuronide is reduced in the two-
column configuration. Mass spectrometry highlights the elution of UV-inactive material eluting 30
minutes after the last phenolic peak. This is seen in Figure A-3 where there is still a total ion count
(TIC) trace after 110 minutes but no UV absorbance.
106
RS (1x column) RS (2x columns)
trans-caftaric acid + 2-S-glutathionyl trans-caftaric acid (GRP) 1.0 2.3
cis and trans isomers of coutaric acid 4.75 8.16
Resolution, RS = (tR1 – tR2) / 0.5(tW1 + tW2) where tR is elution time and tW is tangent baseline width