The Australian Wine

Research Institute

Copper, the good, the bad,

the ugly

Dr Eric Wilkes

Commercial Services

The Australian Wine

Research Institute Why do we use copper at all?

To get rid of the bad smells of course.

Copper has a long history of use in beverage production to

remove unpleasant sulfur related smells.

The Australian Wine

Research Institute What are these smells?

Literature

ReviewAWRI

Hydrogen Sulfide H2S rotten egg, sewage like 1 nd - 370 nd - 56

Methanethiol MeSHrotten cabbage, burnt rubber,

putrefacation1.5 nd - 16 nd - 11

Ethanethiol EtSHonion, rubbery, burnt match,

sulfidy, earthy1.5 nd - 50 nd - 3

Dimethyl sulfide DMSblackcurrant , cooked cabbage,

asparagus, canned corn, molasses25 nd - 474 nd - 980

Carbon disulfide CS2sweet, ethereal, slight green ,

rubber, sulfidy, chokingly repulsive 5 nd - 18 nd - 140

Diethyl sulfide DES garlic, rubbery 1 nd - 10 nd

Methyl thioacetate MeSAc sulfurous, cheesy, egg 40 nd - 115 nd - 53

Dimethyl disulfide DMDSvegetal, cabbage, intense onion-

like (at high levels)10 nd - 22 nd - 2

Ethyl thioacetate EtSAc sulfurous, garlic, onion 70 nd -180 nd - 32

Diethyl disulfide DEDS bad smelling, onion 4 nd - 85 nd - 1.5

Detected (ug/L)

Odour DescriptorLow MW Sulfur Compound

Aroma

Threshold

(ug/L)

The Australian Wine

Research Institute It can be very effective.

H2S H2S + Cu2+

CuS

mercaptan CH3CH2SH + Cu2+

Cu(CH3CH2S)2

DMDS CH3S-SCH3 + Cu2+

unreactive

DMS CH3SCH3+ Cu2+

unreactive

oxidation reduction

The Australian Wine

Research Institute But why doesn’t it always work?

Why does my wine go stinky again after it is treated in tank?

Why don’t the bench trials always reflect what I see in tank?

It is all a question of equilibrium!

The Australian Wine

Research Institute Its not quite as simple as you may think!

3H2S + CH3 C

O

O

2 CH3 CH

SH

OH

1-hydroxy-ethanethiol

CH3 CH

SH

SH

S

S S

SS

S S

SS

CH3 CS

C CH3

SHSH

H H SS

S

1,1-ethandithiol

intense rubbery or sulphury odour

cis/trans-3,6-dimethyl-1,2,4,5-tetrathiane

rubbery chemical aroma

cis/trans-2,5-dimethyl-1,2,4-trithiolane

spicy meat, meat like or allium aroma

cis/trans-4,7-dimethyl-1,2,3,5,6-pentathiepane

meat like aroma

bis(1-mercaptoethyl)sulfide

[O][O]

[O]

H2S

-H2S

H2S

H2S

Too Hard

The Australian Wine

Research Institute If only it was that simple!

CH3S _ H

methanethiol

(mercaptan) 1.5 µg/L

O

║

CH3C _ SCH3

methyl thioacetate 40 µg/L

OSC

Oxidised Sulfur

compounds >10 µg/L

H2S

hydrogen sulfide 1 µg/L

Wine components

CH3OH or CH3CHO

methanol acetaldehyde ?

The Australian Wine

Research Institute Myth busting!

All the copper I add drops out as insoluble sulfide!

Sulfide Copper Sulfate

1-2 μg/l 0.000002 g/l

0.5ppm 0.0005 g/l

It is not unusual to see copper values increase at exactly the same rate as addition.

The Australian Wine

Research Institute Downsides of residual copper

Hazes

Increased loss of 3-MH and 3-MHA

More rapid loss of SO2

Increases in sulfides

The Australian Wine

Research Institute Hazes and protein instability.

0.15

0.17

0.19

0.21

0.23

0 0.2 0.5 0.75

NTU

Copper

Turbidity (heated) fined

0.00

5.00

10.00

15.00

0 0.2 0.5 0.75 1.5

NTU

Cu ppm

Turbidity (heated) Increased copper levels in bottled wine are well know to increase of protein instability. Generally recommended to keep levels below 0.5 ppm, but limit depends on the wine.

The Australian Wine

Research Institute Increased loss of 3-MH and 3-MHA

3-MH (3-Mercaptohexan-1-ol) 3-MHA (3-Mercaptohexan-1-ol acetate)

50.0

55.0

60.0

65.0

70.0

75.0

80.0

85.0

90.0

0 14 28

3-M

H [n

mo

l/L

]

time [days]

control

Cu

Dr. Mandy Herbst-Johnstone

School of Chemical Sciences

The University of Auckland

The Australian Wine

Research Institute More rapid loss of SO2

After just six months in bottle!

Danilewicz, J. (2007). Interaction of sulfur dioxide, polyphenols, and oxygen in a wine-model system: Central role of iron and copper. American journal of enology and ….

SO2 cannot interact with O2 directly. It requires the presence of metals such as copper and iron.

14

15

16

17

18

19

0 0.2 0.5 0.75 1.5

FSO

2

Sulfur Dioxide (free)

The Australian Wine

Research Institute Increases in sulfides

0

0.5

1

1.5

2

2.5

3

Cu

0 m

g/L

Cu

0.2

mg/

L

Cu

0.5

mg/

L

Cu

0.7

5 m

g/L

Cu

1.5

mg/

L

H2S

H2S - Unfined

H2S - Fined

0

1

2

3

4

5

6

7

Cu

0 m

g/L

Cu

0.2

mg/

L

Cu

0.5

mg/

L

Cu

0.7

5 m

g/L

Cu

1.5

mg/

L

MeSH

MeSH - Unfined

MeSH - Fined

After just 2 months this chardonnay was already showing the impact of increased copper.

The Australian Wine

Research Institute After 6 months.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 0.2 0.5 0.75 1.5

H2

S

Added Cu mg/l

H2S

H2S -Unfined

H2S - fined

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0 0.2 0.5 0.75 1.5

Me

SH

Added Cu mg/l

MeSH

MeSH - unfined

MeSH -fined

While the MeSH has gone down, we don’t know where! The H2S seems to be maxing at typical copper levels.

The Australian Wine

Research Institute fined / unfined?

Fining with Bentonite

took the wine from 0.2 to

0.5 mg/L of Iron.

R² = 0.9204

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.0 1.0 2.0 3.0 4.0 5.0 6.0

H2S

Cu/Fe

Relationship between Cu/Fe and H2S

H2S - Average

1.5 Cu Adds

Cu/Fe ratio critical to H2S levels.

At really high copper levels other stuff happens

The Australian Wine

Research Institute Isn’t this just driven by the closure?

0.00

2.00

4.00

6.00

8.00

10.00

12.00

0 5 10 15 20 25 30 35 40

Me

SH

Months in Bottle

MeSH with time Average results for 9 different closures.

For at least the first 2 years the differences are no greater than impact of metals in other trials

Final level does not correlate with closure OTR!

OTR

Pattern typical of what we see as the available O2 / SO2 environment changes.

The Australian Wine

Research Institute How bad could it get?????

Clare Valley Riesling after 8 months.

0

10

20

30

40

50

60

70

0 0.04 0.16 0.53

H2S

Co

ncen

trati

on

pp

b

Cu Concentration ppm

Ralative Amounts of Cu v's H2S Remember, the threshold for is about 1 for most people!

The Australian Wine

Research Institute Why the differences between wines?

No such thing as free copper in wine.

It is all interacting in some way with the different species in wine.

Some of these prevent copper getting involved in the oxidation/

reduction chemistry.

Others don’t!

Incredibly important to tailor copper additions to the wine in

question.

Never just make a standard addition!

The Australian Wine

Research Institute The wines in front of you.

Carbon disulfide Dimethyl sulfide Hydrogen sulfide Methanethiol Methyl thioacetate

Wine 1 Red Control 2.0 73.7 <1 <1 6.4

Wine 2 Red 0.5mg/L Cu 2.3 87.0 1.7 <1 7.4

Wine 3 Red 0.75 mg/L Cu 1.6 65.7 1.4 1.1 6.7

Wine 4 White Control <0.5 21.0 0.9 4.5 <5

Wine 5 White 0.5mg/L Cu <0.5 21.7 10 4.2 <5

Wine 6 White 0.75 mg/L Cu <0.5 21.0 14 3.9 <5

0.0

0.5

1.0

1.5

2.0

2.5

Carbon disulfide

Hydrogen sulfide

Methanethiol

Red Wines

Wine 1

Wine 2

Wine 3

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

Carbon disulfide Hydrogen sulfide

Methanethiol

White Wines

Wine 4

Wine 5

Wine 6

The Australian Wine

Research Institute When is it ok to use copper?

Best time to add is at the end of fermentation

Eliminate the potential precursors as early as possible

Use the solids to remove as much of the excess copper as possible

If you have to do it later

Know what sulfur compounds you are treating (copper/cadmium test)

Add the minimum amount of copper.

Give it time to stabilize before bottling.

Test the copper levels before and after addition.

Never add on the day of bottling.

The Australian Wine

Research Institute Summary

Copper can be incredibly effective in preventing the development

of off sulfur characters.

However if excess is left in the wine it can lead to

the development of the same undesirable characters

hazes

degradation of SO2 levels and desirable sulfur compounds

Copper is best added early in the wines life when fermentation

solids can help to remove it.

Later additions can lead to a build up of available copper.

Not all copper is striped from wine post addition as sulfides.

Careful trials can lead to successful management of copper

levels.

The Australian Wine

Research Institute Acknowledgements

Paul Smith

Marlize Viviers

Mark Smith

Martin Day

Mandy Herbst-Johnstone

(Uni of Auckland)

Treasury Wine Estates

The rest of the AWRI team.

The Australian Wine

Research Institute Thankyou

Questions?