2. Experimental Design Assaying volatile thiols by GC/MS The extent of 3MH and 3MHA loss in a model...
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2. Experimental Design Assaying volatile thiols by GC/MS The extent of 3MH and 3MHA loss in a model wine solution (ultrapure water [MilliQ]/EtOH [88:12 v/v]; 5g/L tartaric acid; pH 3.5) after four weeks was monitored by GC/MS 1 . Analysis of polyphenols and glutathione by RP-HPLC A reversed phase-HPLC method allowed the separation of polyphenols and glutathione present in Sauvignon Blanc wines by direct injection of the sample using a gradient elution with a ternary solvent mixture and a diode array detector and electrochemical detector to identify and quantify the polyphenols and glutathione, respectively 2,3 . References: 1 Tominaga,T., Murat, M.L., Dubourdieu, D. (1998). J. Agric. Food Chem. 46: 1044-1048. 2 Kilmartin, P.A., Zou, H., Waterhouse, A.L. (2002). Am. J. Enol. Vitic. 53: 294- 302. 3 Smith, N.C., Dunnett, M., Mills, P.C. (1995). J. Chromatogr. B. 673: 35-41. 1. Introduction The volatile thiols 3-mercaptohexan-1-ol (3MH) and 3- mercaptohexan-1-ol acetate (3MHA) contribute to the fruity aroma of Vitis vinifera L. var. Sauvignon blanc wines (fig. 1), and improving their stability is seen as key to retaining fresh, fruity characters in these wines for a longer period of time. Fig. 1: Volatile thiols involved in Sauvignon blanc aroma The loss of 3MH and 3MHA has been linked to polyphenol oxidation involving the hydroxycinnamic acids in white wines, a process which is inhibited by the presence of antioxidants such as glutathione and sulfur dioxide. In order to understand the flavour change 31 New Zealand (18 months old) and 21 overseas wines (12 to 24 months old) were screened for glutathione and polyphenol levels. The influence of varying levels of the polyphenol caffeic acid, dissolved oxygen, and the antioxidants sulfur dioxide and glutathione were tested in a model wine medium to determine the extent of 3MH and 3MHA loss. Role of Antioxidants and Polyphenols in the Stability of Sauvignon Blanc Aromas M. Herbst 1 , P.A. Kilmartin 1 and L. Nicolau 1 1 Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand [[email protected]] Acknowledgements This research is supported by the New Zealand Foundation for Research, Science and Technology. The author acknowledges the support of the Wine Science group at the University of Auckland. science wine 3-Mercaptohexan-1-ol 3-Mercaptohexan-1-ol acetate acetate (Passion fruit) 3-Mercaptohexan-1-ol 3-Mercaptohexan-1-ol (Grapefruit) 3. Results 4. Conclusions The low glutathione levels (~ 0.8 mg/L or less in 18 month old New Zealand Sauvignon blanc wines) might be a reason for the instability of the volatile thiols 3MH and 3MHA in bottled wines. The level of hydroxycinnamates, the initial substrate of wine oxidation, was similar across New Zealand regions and compared to overseas wines. The addition of sulfur dioxide and glutathione lessened the decrease in 3MH and 3MHA over a four week period, whereas in the presence of oxygen and caffeic acid 3MH and 3MHA declined by 37 % and 57 %, respectively. 3MHA was a little less stable than 3MH in this study. HPLC response Fig. 3: Survey of glutathione levels in Sauvignon blanc wines from 6 different countries 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Fig. 4: Total hydroxycinnamates in Sauvignon blanc wines from 6 different countries 0 10 20 30 40 50 60 70 Hawkes Bay Sout h A fric a Marlborough Wairarapa France C hil e USA Aust ral ia N ew Zealand Tab. 1: Evolution of 3MH and 3MHA in model wine after 28 days storage at 20ºC 4 Fig 2: HPLC of Sauvignon blanc Sample Sample % 3MH % 3MH % 3MHA % 3MHA Day 0 Day 0 Control Control 100 100 (3000 (3000 ng/L) ng/L) 100 100 (700 (700 ng/L) ng/L) Day 28 Day 28 Control Control 56 56 41 41 Control + SO Control + SO 2 2 68 68 65 65 Control + GSH Control + GSH 67 67 61 61 Control + SO Control + SO 2 + GSH + GSH 67 67 60 60 Control + caffeic Control + caffeic acid acid 65 65 48 48 Control + caffeic Control + caffeic acid + O acid + O 2 2 63 63 43 43 GSH [mg/L] Total hydroxycinnamates [mg/L] 4 The values shown in tab. 1 are means of triplicates of each treatment. SO 2 (30 mg/L), GSH (10 mg/L), caffeic acid (100 mg/L), O 2 (> 8 ppm) Change in glutathione levels 1 = glutathione; 2 = caftaric acid; 3 = GRP; 4 = t-coutaric acid; 5 = fertaric acid; 6 = caffeic acid; 7 = p-coumaric acid; 8 = ferulic acid; 9 = t-resveratrol
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Transcript of 2. Experimental Design Assaying volatile thiols by GC/MS The extent of 3MH and 3MHA loss in a model...
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2. Experimental DesignAssaying volatile thiols by GC/MSThe extent of 3MH and 3MHA loss in a model wine solution (ultrapure water [MilliQ]/EtOH [88:12 v/v]; 5g/L tartaric acid; pH 3.5) after four weeks was monitored by GC/MS1.
Analysis of polyphenols and glutathione by RP-HPLCA reversed phase-HPLC method allowed the separationof polyphenols and glutathione present in Sauvignon Blanc wines by direct injection of the sample using a gradient elution with a ternary solvent mixture and a diode array detector and electrochemical detector to identify and quantify the polyphenols and glutathione, respectively2,3.
References:1 Tominaga,T., Murat, M.L., Dubourdieu, D. (1998). J. Agric. Food Chem. 46: 1044-1048.2 Kilmartin, P.A., Zou, H., Waterhouse, A.L. (2002). Am. J. Enol. Vitic. 53: 294-302.3 Smith, N.C., Dunnett, M., Mills, P.C. (1995). J. Chromatogr. B. 673: 35-41.
1. IntroductionThe volatile thiols 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexan-
1-ol acetate (3MHA) contribute to the fruity aroma of Vitis vinifera L. var. Sauvignon blanc wines (fig. 1), and improving their stability is seen as key to retaining fresh, fruity characters in these wines for a longer period of time.
Fig. 1: Volatile thiols involved in Sauvignon blanc aroma
The loss of 3MH and 3MHA has been linked to polyphenol oxidation involving the hydroxycinnamic acids in white wines, a process which is inhibited by the presence of antioxidants such as glutathione and sulfur dioxide.
In order to understand the flavour change 31 New Zealand (18 months old) and 21 overseas wines (12 to 24 months old) were screened for glutathione and polyphenol levels.
The influence of varying levels of the polyphenol caffeic acid, dissolved oxygen, and the antioxidants sulfur dioxide and glutathione were
tested ina model wine medium to determine the extent of 3MH and 3MHA loss.
Role of Antioxidants and Polyphenols in the Stability of Sauvignon Blanc Aromas
M. Herbst1, P.A. Kilmartin1 and L. Nicolau1
1Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand
Acknowledgements
This research is supported by the New Zealand Foundation for Research, Science and Technology. The author acknowledges the support of the Wine Science group at the University of Auckland.
science wine
3-Mercaptohexan-1-ol 3-Mercaptohexan-1-ol acetateacetate (Passion fruit)
3-Mercaptohexan-1-ol3-Mercaptohexan-1-ol(Grapefruit)
3. Results
4. Conclusions The low glutathione levels (~ 0.8 mg/L or less in 18 month old New Zealand Sauvignon blanc wines) might be a reason for the instability of the volatile thiols 3MH and 3MHA in bottled wines. The level of hydroxycinnamates, the initial substrate of wine oxidation, was similar across New Zealand regions and compared to overseas wines.
The addition of sulfur dioxide and glutathione lessened the decrease in 3MH and 3MHA over a four week period, whereas in the presence of oxygen and
caffeic acid 3MH and 3MHA declined by 37 % and 57 %, respectively. 3MHA was a little less stable than 3MH in this study.
HPLC
resp
onse
Fig. 3: Survey of glutathione levels in Sauvignon blanc wines from 6 different countries
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Fig. 4: Total hydroxycinnamates in Sauvignon blanc
wines from 6 different countries
0
10
20
30
40
50
60
70
Hawkes Bay
Sout
h Af
rica
MarlboroughWairarapa
Fran
ce
Chile
USA
Aust
ralia
New
Zea
land
Tab. 1: Evolution of 3MH and 3MHA in model wine after 28 days storage at 20ºC4
Fig 2: HPLC of Sauvignon blanc
SampleSample % 3MH% 3MH % 3MHA% 3MHA
Day 0Day 0
ControlControl 100 100
(3000 (3000 ng/L)ng/L)
100 100
(700 ng/L)(700 ng/L)
Day 28Day 28
ControlControl 5656 4141
Control + SOControl + SO22 6868 6565
Control + GSHControl + GSH 6767 6161
Control + SOControl + SO22 + GSH + GSH 6767 6060
Control + caffeic acidControl + caffeic acid 6565 4848
Control + caffeic acid + Control + caffeic acid + OO22
6363 4343
GS
H [
mg
/L]
Tota
l h
yd
roxyci
nn
am
ate
s [m
g/L
]
4 The values shown in tab. 1 are means of triplicates of each treatment. SO2 (30 mg/L), GSH (10 mg/L), caffeic acid (100 mg/L), O2 (> 8 ppm)
Change in glutathione levels
1 = glutathione; 2 = caftaric acid; 3 = GRP; 4 = t-coutaric acid; 5 = fertaric acid; 6 = caffeic acid; 7 = p-coumaric acid; 8 = ferulic acid; 9 = t-resveratrol
