New Ideas for Measuring
Oxidation
Andrew L. Waterhouse
Collaborators
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Maurizio Ugliano
Bruce Currie
Stephane Vidal
Jean-Baptist Dieval
Olav Aagaard
Mauri Anderson
Alexander Chassy
Wine Oxidation Reactions
Y
Fe+2
O2
H+
Fe+3
RCH2OH
RCHO
(Hydroperoxyl
radical)
(Peroxyl radical)
Fe+3
Fe+2
(Semiquinone radical)
(Hydrogen peroxide)
SO2
X
(Quinone)
Managing Wine Oxidation
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Oxygen is consumed
Quinone reversal to phenol
Limit Fenton oxidation
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Quench H2O2
Reactions of Fenton products
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Color development
Measure Oxygen Consumed!
Measure Oxygen Consumed in Bottle?
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Oxygen entering bottle
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At bottling
From closure
Oxygen transfer through closure
Subtract residual oxygen
Balance: consumed oxygen
How can we measure oxygen entering
bottle
Oxygen Measurement in Bottles, etc
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Device emits blue
flashes
Dots in container
luminesce with red
light
Rate of decay is
related to [O2]
Measuring Oxygen Entering Bottle
Model Bottle
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Diéval JB, Packag. Technol. Sci. 2011; 24: 375–385
Provides prediction for the same closures!
Oxygen Consumption by Wine
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Add oxygen entering bottle
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Oxygen at bottling
Oxygen from closure transmission (model bottle)
Subtract current O2 (Nomasense)
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Difference is Total Consumed Oxygen, TCO
Oxygen that has been consumed by wine
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Apply to an experiment
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Interaction of Wine Prep, Closures
Experiment on Chardonnay
 Chardonnay Wines
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Four Closures
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Oak barrel vs SS barrel
Lees aging vs no lees
Light
Premium
Premium, 4% O2
Premium, N2
Accelerated Aging Experiment
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High O2 at bottling
Measurements
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O2 by Nomasense
Carbonyls by DNPH
Phenolics by HPLC
SO2 by Ripper
others
DO and HSO
Chardonnay wine in barrel with no lees
6
C1 DO
5
C2 DO
C2 4% DO
4
C2 N2 DO
C1 HSO
3
C1 HSO
C1 4% HSO
2
C1 N2 HSO
1
0
0
50
100
150
200
250
300
350
TCO Data
07 Chard Ba no lees
20
18
16
TCO (ppm)
14
12
Light
Prem
10
Prem4%
PremN2
8
6
4
2
0
0
50
100
150
200
Days
250
300
350
Free SO2 Data
07 Chardonnay Ba no Lees
30
25
FSO2 (ppm)
20
Light
Prem
15
Prem 4%
Prem N2
10
5
0
0
50
100
150
200
Days
250
300
350
Sulfur Dioxide and Oxygen
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Theoretical Balanced Reaction
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Mass ratio, 4 SO2 to O2
So, with 4/1 ratio of consumption
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2 SO2 + O2 → 2 SO3
Balanced reaction
Complete protection from oxidation
Ratio below 4: oxidation of other
components
Antioxidant Reactions of SO2
Fe+2
O2
H+
Fe+3
RCH2OH
RCHO
(Hydroperoxyl
radical)
(Peroxyl radical)
Fe+3
Fe+2
(Semiquinone radical)
(Hydrogen peroxide)
SO2
SO2
H2O
(Quinone)
Consumed Free SO2/TCO
At End of Experiment
Different Consumption Ratios
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Lees aged wine had higher
Consumed SO2/TCO
How can we explain different ratios?
Lees aging increases ratio
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WM’s report that lees aging is
protective
Lees aged wines had less pyruvic acid
Model Quinone SO2 reaction
Effect of Pyruvic Acid
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Decreases the ability of SO2 to
reduce quinone
Compromises the antioxidant
effect of SO2
Need to understand which
wine components are
affecting these reactions
“Weak binders”
unreactive
SO2
RSH
Measurement of Free SO2
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Titration with I2
Appearance of excess I2 after SO2
depleted
I-
I2
SO2
k, fast
Weak SO2 Binding Agents
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Pyruvate
Alpha-keto glutaric acid
Galacturonic Acid
Other aldehydes, ketones
Barrel Aging on Lees
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Lower level of pyruvic acid!
Yeast lees or bacteria seem to
metabolize aldehydes and ketones,
reducing them to the alcohol form
Thus, the free SO2 as currently
measured, is more available for
protective reactions
So, during oxidation, the consumed
SO2/TCO ratio is higher
Application of SO2/TCO Ratio
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May be predictive of protection by
SO2
Measurement takes time
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At least two time points needed
Need time to consume both oxygen
and SO2
Could a titration of SO2 versus
SO2/TCO Ratio show what level of
SO2 could be protective?
Improved SO2 Measurement
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Predictive of reactive SO2
Quick measurement
Avoids dilution or equilibration effect
from titration or other treatment
Summary
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TCO in bottle is a key new measurement
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Comparison of TCO vs SO2 consumed
appears to be useful
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Ratio of 4 indicates no oxidation products
Ratio below 2 leads to significant oxidation
Value below 4 needed for developmentphenolics
Protection by “free” SO2 is not linear
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Based on consistent closures
Interference by carbonyls?
Free SO2 measures need improvement
Major Support
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Nomacorc
American Vineyard Foundation