New Ideas for Measuring Oxidation

Andrew L. Waterhouse

Collaborators Maurizio Ugliano Bruce Currie Stephane Vidal Jean-Baptist Dieval Olav Aagaard Mauri Anderson Alexander Chassy

Wine Oxidation Reactions

SO2

X

Y

O2

Fe+2 Fe+3

Fe+2

Fe+3

(Semiquinone radical) (Hydrogen peroxide)

(Peroxyl radical)

(Quinone)

(Hydroperoxylradical)

RCH2OHRCHO

H+

O HO H

O ·O H

O

H O ·

O HOH

OH O ·

H +

O ·H

OO

C ·R HOH

+

Managing Wine Oxidation

Oxygen is consumed Quinone reversal to phenol Limit Fenton oxidation

Quench H2O2

Reactions of Fenton products Color development

Measure Oxygen Consumed!

Measure Oxygen Consumed in Bottle? Oxygen entering bottle

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 Device emits blue

flashes Dots in container

luminesce with red light

Rate of decay is related to [O2]

Measuring Oxygen Entering BottleModel Bottle

Diéval JB, Packag. Technol. Sci. 2011; 24: 375–385 Provides prediction for the same closures!

Oxygen Consumption by Wine Add oxygen entering bottle

Oxygen at bottling Oxygen from closure transmission (model bottle) Subtract current O2 (Nomasense)

Difference is Total Consumed Oxygen, TCO

Oxygen that has been consumed by wine

Apply to an experiment

Interaction of Wine Prep, ClosuresExperiment on Chardonnay Chardonnay Wines

Oak barrel vs SS barrel Lees aging vs no lees

Four Closures Light Premium Premium, 4% O2 Premium, N2

Accelerated Aging Experiment High O2 at bottling

Measurements

O2 by Nomasense Carbonyls by DNPH Phenolics by HPLC SO2 by Ripper others

DO and HSO

TCO Data

07 Chard Ba no lees

0

2

4

6

8

10

12

14

16

18

20

0 50 100 150 200 250 300 350

Days

TC

O (

pp

m) Light

Prem

Prem4%

PremN2

Free SO2 Data07 Chardonnay Ba no Lees

0

5

10

15

20

25

30

0 50 100 150 200 250 300 350

Days

FS

O2

(pp

m) Light

Prem

Prem 4%

Prem N2

Sulfur Dioxide and Oxygen Theoretical Balanced Reaction

2 SO2 + O2 → 2 SO3

Mass ratio, 4 SO2 to O2

So, with 4/1 ratio of consumption Balanced reaction Complete protection from oxidation

Ratio below 4: oxidation of other components

Antioxidant Reactions of SO2

SO2

SO2

H2O

O2

Fe+2 Fe+3

Fe+2

Fe+3

(Semiquinone radical) (Hydrogen peroxide)

(Peroxyl radical)

(Quinone)

(Hydroperoxylradical)

RCH2OHRCHO

H+

O HO H

O HO H

O ·O H

O

H O ·

O HOH

OH O ·

H +

O ·H

OO

C ·R HOH

+

Consumed Free SO2/TCOAt End of Experiment

Different Consumption Ratios Lees aged wine had higher

Consumed SO2/TCO How can we explain different

ratios? Lees aging increases ratio

WM’s report that lees aging is protective

Lees aged wines had less pyruvic acid

Model Quinone SO2 reaction

Effect of Pyruvic Acid 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”RSH

unreactive

SO2

O HO H

OO

O

OH

O HO H

SR

R2R1

SO3-

R1 R2

Measurement of Free SO2

Titration with I2 Appearance of excess I2 after SO2

depleted

I2I-

k, fast

SO2

O OH

R2R1

SO3-

R1 R2+

Weak SO2 Binding Agents

Pyruvate Alpha-keto glutaric acid Galacturonic Acid Other aldehydes, ketones

Barrel Aging on Lees 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 May be predictive of protection by SO2

Measurement takes time 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

Predictive of reactive SO2

Quick measurement Avoids dilution or equilibration

effect from titration or other treatment

Summary TCO in bottle is a key new measurement

Based on consistent closures

Comparison of TCO vs SO2 consumed appears to be useful Ratio of 4 indicates no oxidation products Ratio below 2 leads to significant oxidation Value below 4 needed for development-phenolics

Protection by “free” SO2 is not linear Interference by carbonyls?

Free SO2 measures need improvement

Major Support

Nomacorc American Vineyard Foundation