Relationship between potentiometric measurements and substances responsible for aroma degradation.
Evaluation the Oxidation “status” of a white wine and in what extent
this measure could be related with the typical aroma of “Oxidative
Spoiled” character :
Index of degradation (ID) measured by sensorial analysis.
Levels of substances responsible for “off-flavors” in white wines.
The “Resistance to Oxidation” (ROX) measured by potentiometric
400
E (mV)
Wine
Potential
1 st -Reduction
Oxidation titration
300
200
100
0
[TiCl3]
Reduction titration
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
-100
-200
-300
E = - 400(mV)
-400
Volume (reducer / oxidant) added (ml)
Redox Sequential Titration : Species captured by PIP
E = 400(mV)
400
E (mV)
Wine
Potential
Reduction titration
650
470
Oxidation titration
360
300
300
210
200
100
0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
-100
2 nd - Oxidation
Dichlorophenol-indophenol
E = - 400(mV)
-200
-300
-400
Potential E (mV)
800
750
•  PIP : Selectively pick out wine fraction more readily oxidized
by dissolved oxygen ( - 400 mV < E < 400 mV) !!!
Volume (reducer / oxidant) added (ml)
Coumaric acid
Vanillic acid
Resveretrol
Malvidins
Ferrulic acid
Rutin
Cafeic acid
Gallic acid
Catechin
Epicatechin
Quercetin
Delphinidin
Myricetin
Ascorbic acid
Potential E (mV)
800
750
•  PIP : Selectively pick out wine fraction more readily oxidized
by dissolved oxygen ( - 400 mV < E < 400 mV) !!!
E = 400(mV)
400
Reduction titration
650
470
Oxidation titration
360
300
300
E (mV)
Wine
Potential
210
Veq OXI
200
Coumaric acid
Vanillic acid
Resveretrol
Malvidins
Ferrulic acid
Rutin
Cafeic acid
Gallic acid
Catechin
Epicatechin
Quercetin
Delphinidin
Myricetin
Ascorbic acid
100
0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
-100
2 nd - Oxidation
Dichlorophenol-indophenol
-200
-400
E = - 400(mV)
Oliveira, C.M, A.C. Silva
Ferreira, P. Guedes de
Pinho and T. Hogg.
J. of Agric. Food Chem.,
2002, 50 (7), 2121-2124.
Veq RED
-300
Volume (reducer / oxidant) added (ml)
mmol [Trichlorotitanium, TiCl3] (REDUCER)
ROX-value = mmol [Dichlorophenolindophenol, PIP] (OXIDANT)
Relationship between potentiometric measurements and substances responsible for aroma degradation.
Phenylacetaldehyde
methional
[2]
[1]
OH
H3C
sotolon
H3C
“Oxidative Spoiled ”
OSW
O
O
[3]
nW
“normal white wine”
nW
OSW
S = 3.2
nW + [1]
S = 5.4
nW + [1] + [2] + [3]
nW + [2]
Similarity
•  The highest value from the similarity tests was
founded when the three compounds were added
nW + [2] + [3]
nW + [1] + [3]
nW + [3]
nW + [1] + [2]
Forced Aging protocol
White Wine
- Group I pH= 3.2 ; [SO2 ]free =12 mg/L ; [O2 ]= 1.0 mg/L
Treatment I
pH = 3.2
Treatment II
SO2 (free) = 50 mg/L
Treatment III
O2 dissolved = 6.5 mg/l
Treatment IV
pH = 4.2
Stored at T = 20 ºC // 40 ºC // 60ºC
Normal Aged white wines :
•  Different Vintages (n=24) Age 1-20 years Old
- Group II •  Same Vintage (n=35) Age 2-3 years Old
- Group III -
Relationship between potentiometric measurements and substances responsible for aroma degradation.
ROX-value : Relation with Sensorial Data
Sensorial Degradation
•  Samples saturated with oxygen
faster aroma degradation !
ROX-value
20
&
18
“Index
16
Degradation”(ID)
14
12
10
8
suffers
6
4
2
0
Control
Abs 420
(nm)
0.800
Abs 420 (nm)
ROX-value
"Index of Degradation" (ID)
0.700
0.600
0.500
0.400
0.300
0.200
0.100
pH3 pH4 O2 SO2 pH3 pH4 O2 SO2 pH3 pH4 O2 SO2
T = 20 ºC
T = 40 ºC
Treatments
T = 60 ºC
0.000
Sensorial Degradation
ROX-value
20
&
18
“Index
16
Degradation”(ID)
14
12
10
8
suffers
6
4
2
0
before
Control
•  Samples saturated with oxygen
faster aroma degradation !
•  Aromatic degradation occurs
chromatic degradation which is in agreement
with published data !
Abs 420
(nm)
0.800
Abs 420 (nm)
ROX-value
"Index of Degradation" (ID)
0.700
0.600
0.500
0.400
0.300
0.200
0.100
pH3 pH4 O2 SO2 pH3 pH4 O2 SO2 pH3 pH4 O2 SO2
T = 20 ºC
T = 40 ºC
0.000
T = 60 ºC
Treatments
•  The ROX-Values curve closely follows the “Index of degradation” curve ! R = 0,8869
Relationship between potentiometric measurements and substances responsible for aroma degradation.
ROX-value : Relation with Key-Odorants
Chemical analysis : Samples from Group I
•  Levels of methional and phenylacethaldehyde are highly dependent on temperature and oxygen regimes :
Useful indicators of “aroma spoilage” !
Oxygen pH3 pH4 SO2 Free
70
60
50
40
30
20
10
0
5
10
15
ROX
methional
Oxygen pH3 pH4 SO2 Free
200
r = 0.8430
0
Phenylethanal (ug/L)
Methional (ug/L)
•  ROX-values, are highly correlated with methional and phenylacethaldehyde, respectively r = 0.8430 and
r = 0.8476 !
25
160
r = 0.8476
120
80
40
0
0
5
10
15
ROX 25
phenylacetaldehyde
Chemical analysis : Samples from Group I
•  Levels of methional and phenylacethaldehyde are highly dependent on temperature and oxygen regimes :
Useful indicators of “aroma spoilage” !
Oxygen pH3 pH4 SO2 Free
70
60
50
40
30
20
10
0
T= 0.5 ug/L
5
10
15
ROX
Oxygen pH3 pH4 SO2 Free
200
r = 0.8430
0
Phenylethanal (ug/L)
Methional (ug/L)
•  ROX-values, are highly correlated with methional and phenylacethaldehyde, respectively r = 0.8430 and
r = 0.8476 !
160
r = 0.8476
120
80
T = 25 ug/L
40
0
0
25
methional
5
10
15
ROX 25
phenylacetaldehyde
ROX
ROX > 10 Concentrations are above the odor threshold !
Relationship between potentiometric measurements and substances responsible for aroma degradation.
ROX-value : application to normal aged wines
•  Samples from Group II : Ranked by ROX-value
Index
Methional Phenylacetaldehyde TDN
(nor area)
Age ROX Degradation (ug/L)
(ug/L)
4.1
5.9
4.2
17
18 13
15
13.0
16.6
8.2
9 12
0.9
2.8
5.3
15
7 11
1.4
7.0
3.3
15
20 11
17
14.5
33.3
5.6
17 10
2.5
6.7
6.8
17
14
9
1.7
4.6
4.0
16
9
17
12
0.8
3.4
5.9
9
4
7.4
10.9
7.0
12
8
7
n.d.
3.9
4.4
12
8
9
14
2.4
4.3
4.8
8
19
n.d.
1.8
4.0
7
7
5
4.7
13.8
9.4
15
7
8
12
n.d.
4.2
8.5
5
6
1.7
4.1
6.2
13
5
7
n.d.
0.9
3.2
9
3
10
7
n.d.
0.9
2.6
3
4
n.d.
0.9
4.2
7
3
6
n.d.
n.d.
1.6
2
2
3
6
n.d.
2.9
6.9
8
2
Abs
420 (nm)
0.495
0.292
0.180
0.322
0.433
0.307
0.252
0.171
0.135
0.218
0.314
0.126
0.231
0.215
0.175
0.167
0.128
0.147
0.122
0.226
•  Samples from Group II : Ranked by ROX-value
Index
Methional Phenylacetaldehyde TDN
(nor area)
Age ROX Degradation (ug/L)
(ug/L)
4.1
5.9
4.2
17
18 13
15
13.0
16.6
8.2
9 12
0.9
2.8
5.3
15
7 11
1.4
7.0
3.3
15
20 11
17
14.5
33.3
5.6
10
17
2.5
6.7
6.8
17
14
9
1.7
4.6
4.0
16
9
17
12
0.8
3.4
5.9
9
4
7.4
10.9
7.0
12
8
7
n.d.
3.9
4.4
12
8
9
14
2.4
4.3
4.8
8
19
n.d.
1.8
4.0
7
7
5
4.7
13.8
9.4
15
7
8
12
n.d.
4.2
8.5
5
6
1.7
4.1
6.2
13
5
7
n.d.
0.9
3.2
9
3
10
7
n.d.
0.9
2.6
3
4
n.d.
0.9
4.2
7
3
6
n.d.
n.d.
1.6
2
2
3
6
n.d.
2.9
6.9
8
2
7
n.d.
1.0
3.5
2
4
4
n.d.
3.6
1.2
1
2
9
n.d.
n.d.
5.4
9
1
1
2
n.d.
2.8
0.1
1
Abs
420 (nm)
0.495
0.292
0.180
0.322
0.433
0.307
0.252
0.171
0.135
0.218
0.314
0.126
0.231
0.215
0.175
0.167
0.128
0.147
0.122
0.226
0.254
0.080
0.194
0.054
Relationship between potentiometric measurements and substances responsible for aroma degradation.
ROX-value : application to normal aged wines
•  Samples from Group II : Ranked by ROX-value
Index
Methional Phenylacetaldehyde TDN
(nor area)
Age ROX Degradation (ug/L)
(ug/L)
4.1
5.9
4.2
17
18 13
15
13.0
16.6
8.2
9 12
0.9
2.8
5.3
15
7 11
1.4
7.0
3.3
15
20 11
17
14.5
33.3
5.6
17 10
2.5
6.7
6.8
17
14
9
1.7
4.6
4.0
16
9
17
12
0.8
3.4
5.9
9
4
7.4
10.9
7.0
12
8
7
n.d.
3.9
4.4
12
8
9
14
2.4
4.3
4.8
8
19
n.d.
1.8
4.0
7
7
5
4.7
13.8
9.4
15
7
8
12
n.d.
4.2
8.5
5
6
1.7
4.1
6.2
13
5
7
n.d.
0.9
3.2
9
3
10
7
n.d.
0.9
2.6
3
4
n.d.
0.9
4.2
7
3
6
n.d.
n.d.
1.6
2
2
3
6
n.d.
2.9
6.9
8
2
• f (ROX) : r = 0.8725
Abs
420 (nm)
0.495
0.292
0.180
0.322
0.433
0.307
0.252
0.171
0.135
0.218
0.314
0.126
0.231
0.215
0.175
0.167
0.128
0.147
0.122
0.226
ID
• f (AGE) : r = 0.7491
• f (Abs 420 nm) : r = 0.6966
20
15
Methional
10
5
0
0.0
5.0
10.0
ROX 15.0
ROX close 10
210
140
Linalool
•  Samples from Group III :
•  Seven samples From Group III analyzed after one year.
•  Five samples from Group III - supplemented with O2,
Stored at 30 ºC (10 days).
Oxygen consumption
(mg/L)
•  The ROX-value for samples (n=35) same Vintage ranged from 0.4 to 4.4.
5.0
Normal aging Oxygen Saturated
4.0
3.0
2.0
r = 0.7176
1.0
0.0
0.0
1.0
2.0
3.0
4.0
ROX_increment
5.0
6.0
•  A positive impact of Oxygen consumption on ROX was observed : r = 0.7176 !
Relationship between potentiometric measurements and substances responsible for aroma degradation.
A potentiometric method based upon a sequence of redox titrations in order to quantify the
“first line of defense” of white wine, against “aroma spoilage” is proposed.
“Resistance to Oxidation” were strongly correlated with the “Index of Degradation” rated
by the
sensorial panel, both in normal aged wines and in “forced aged”
experiments, respectively r = 0.8725 and r = 0.8869.
ROX-values higher than 10 the concentration of methional and phenylacetaldehyde were
respectively above odor threshold.
Finally, it was observed a positive relationship between consumed oxygen and the