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

More documents

Recommendations

Info

AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines Figure 6-3: Mean difference of sensory ratings of phenolic fractions extracted from three commercial wines from the sensory ratings of a base wine. #,*,** indicate difference at 10, 5 and 1% respectively. Page | 54 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 Astringency Viscosity Bitterness Burning Acidity Acid AT ** GewurFT GewurF1 GewurF2 GewurF3 Astringency Viscosity Bitterness Burning Acidity Acid AT FianoFT FianoF1 FianoF2 FianoF3 Astringency Viscosity Bitterness Burning Acidity Acid AT RiesFT RiesF1 Ries2 RiesF3 * * #
AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines 7 The Effect of Caftaric Acid and Grape Reaction Product on the Sensory Character of Model Wine 7.1 Introduction The tartaric acid ester of caffeic acid, known as caftaric acid and its derivative 2-S-glutathionyl caftaric acid, better known as Grape Reaction Product or GRP, are among the most dominant phenolics in Australian white wines. GRP forms when polyphenol oxidase enzymes oxidise caftaric acid to the quinone, which then non-enzymatically reacts with the grape peptide glutathione. The relative amount of GRP to caftaric acid in wine can be increased by utilising winemaking practices that involve oxidative juice handling. Their abundance and ability to be influenced by winemaking made caftaric acid and GRP key molecules of interest. As such, they were isolated and their taste properties quantified. 7.2 Methods 7.2.1 Isolation of Caftaric Acid and GRP for Sensory Analysis GRP and caftaric acid were extracted from 36 L of 2010 vintage wines made as part of this project and described in Chapter 8. The wines used were made from the light and heavy pressings of Chardonnay (18 L), Viognier (4.5 L) and Riesling (13.5 L). Whole phenolics were extracted from each of the wines by acidifying them with 0.1M HCl and loading them onto a 500 mL chromatography column packed with Amberlite FPX66 resin (Dow, Camberwell, Australia). The column content was washed with 2 L water before eluting the phenolics with 2 L of 96% v/v ethanol. The eluate was chilled at 4°C overnight before being dried under vacuum at 40°C. A Quattro Mk II high speed counter-current chromatography (HSCCC) device (AECS-QuikPrep Ltd, Bridgend, S. Wales, UK) equipped with a 500 mL stainless steel preparative scale coil (2.16 mm i.d tubing) was used to fractionate the whole phenolics and collect GRP and caftaric acid. The device was used with a Waters 600E controlled pump and two single wavelength UV detectors (UPC-900 Amersham Biosciences for A280and a GBC LC 1210 for A320) and a fraction collector (Amersham Pharmacia Biotec). A two stage separation was used. Full details of the methods development are given in Appendix A.2. Firstly, GRP was isolated from the whole phenolic extract using a highly polar butanol : water (1:1) system. For each of six runs, whole phenolics from 6 L of wine were dissolved in 50 mL of a mixture 55
Page 1 and 2:
Identification of the major drivers
Page 3 and 4: AWRI: Identification Of The Major D
Page 53: AWRI: Identification Of The Major D
Page 105 and 106:
AWRI: Identification Of The Major D
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
RT (min) AWRI: Identification Of Th
Page 115 and 116:
RT (min) AWRI: Identification Of Th
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139:
show all

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

Create successful ePaper yourself

Delete template?

Save as template?