reduction redux – the good, the bad and the nutty the ......reduction redux – the good, the bad...
TRANSCRIPT
Presented by Adrian CoulterSenior Oenologist —
AWRI
Reduction Redux –
The Good, the Bad and the Nutty
The closure issues
1999 Semillon wine bottled using 14 different closures
14 different wines!14 different closures ⇒
Range of color 28 months after bottling
OD420 ≈
0.14 au OD420 ≈
0.19 au
1+1
Ref 2
Ref 3
Altec
Ref 2Ref 3
Altec
Ref 2
Ref 3
Ref 2Ref 3
Altec
Ref 2
Ref 3
Altec
Ref 2Ref 3
Ref 2Ref 3
Ref 2
Ref 3
Altec
citrus
limeoverall aroma
honey
toasty
oxidised
TCA
struck flint
rubberROTE
ROTEROTE
ROTEROTE
ROTE
Altec
Altec
1+1
1+1
1+1
1+1
1+1
1+11+1
ROTEROTE
PC2 (19%)
PC1 (60%)
PCA ‘map’
of 63 month aroma data (1999 Semillon wine)
Altec
Wine ‘development’
•
is closely connected with oxidation–reduction phenomena (redox reactions)
•
depends on a whole series of factors relating to the wine’s composition and storage conditions
Post-bottling:
depends on wine composition, storage conditions and the properties of the closure
Wine ‘development’ oxidation/reduction,
andconsumer satisfaction
Bottling•
Dissolved oxygen•
Oxygen in headspace
•
Oxygen permeability of closures
•
Filling height•
SO2
Wine composition•
Dissolved oxygen•
Ascorbic acid•
SO2•
Phenolic compounds•
Metal ions•
Flavour compounds•
Oak phenolics•
Fermentation-derived compounds (thiols)
•
…….
Wine storage•
Permeability of closures (transfer of gases in and out of the bottle, closure type, storage position)
•
Flavour scalping•
Temperature•
Time•
…….
AWRI ‘commercial closure trial’ bottled September 2002
ROTE (Auscap, tin liner) -
four treatments at bottling
“Low”
filling height (48mm ullage,Free SO2
38 mg/L)
“High”
filling height(30mm ullage,Free SO2
39 mg/L)
“Low”
filling height + SO2
(47mm ullage,Free SO2
54 mg/L)
“High”
filling height + SO2
(29mm ullage,Free SO2
59 mg/L)
Free SO2
(mg/L)
Struck flint aroma score
Relationship between free SO2 and ‘struck flint’ aroma score: 24 months storage
0
0.5
1.0
1.5
2.0
High
High+SO2
Low
Low+SO2
10 15 20 25 30 35 40 45
Low+SO2
Low+SO2
Low+SO2
High+SO2
High+SO2
High+SO2
HighHighHigh
Low
LowLow
Sulfur equilibrium in wine
methanethiol1.5 μg/L
CH3
S-H
methyl thioacetate40
μg/L
CH3
C – SCH3
dimethyl disulfide10 μg/L
CH3
S
–
SCH3
reduc
tion
oxida
tionhydrolysis
acetylation
║O
Free SO2
(mg/L)
Struck flint aroma score
2.5
0
0.5
1.0
1.5
2.0
15 20 25 30 35 40 45
Low+SO2
High
Low
High+SO2
Relationship between free SO2 and ‘struck flint’ aroma score: 24 months storage (n=4)
Free SO2
(mg/L)
Mean score for
Rubber
0
0.5
1.0
1.5
2.0
0 5 10 15
ROTE
ROTE
ROTEROTE
ROTEROTEROTE
ROTE
AltecAltec
Altec
AltecAltec
Altec
Altec Altec1+1
1+1
1+11+1
1+1
1+1
1+1
1+1
Ref 3
Ref 3
Ref 3Ref 3
Ref 3
Ref 3
Ref 3
Ref 3
Ref 2Ref 2
Ref 2Ref 2
Ref 2
Ref 2 Ref 2
Ref 2
Free SO2
concentration and ‘rubber’
aroma score: 63 months storage
Mean score for Struck
flint
Free SO2
(mg/L)
0
1.0
2.0
3.0
0 5 10 15
ROTEROTEROTE
ROTEROTE
ROTEROTE
ROTE
ROTE
Altec
AltecAltec
AltecAltec
Altec
AltecAltec
Ref 2
Ref 2Ref 2Ref 2 Ref 2Ref 2 Ref 2
Ref 2
1+1
1+11+1
1+1
1+11+11+1
1+1Ref 3Ref 3Ref 3
Ref 3
Ref 3Ref 3Ref 3
Ref 3
Free SO2
concentration and ‘struck flint’ aroma score: 63 months storage
Wines bottled with low oxygen permeation closures are more likely
to develop reductive character in bottle, if those wines have a
propensity to become reductive
Development of ‘reductive’
characters in wine after bottling
1 2 3 4 5 6 7 8 9 10 11 12
0.0
0.1
0.2
0.3
0.4
0.5
Panel mean scores for the attribute reduced
ChardonnaySauvignon BlancSemillon Sauvignon Blanc
Bottle number
Attr
ibut
e m
ean
scor
e
1 2 3 4 5 6 7 8 9 10 11
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Panel mean scores for the attribute TCA
ChardonnaySauvignon BlancSemillon Sauvignon Blanc
Bottle number
Attr
ibut
e m
ean
scor
e
ChardonnaySauvignon BlancSemillon Sauvignon Blanc
Panel mean scores for the attribute oxidised
1 2 3 4 5 6 7 8 9 10 11 12
0.0
0.1
0.1
0.2
0.2
0.3
0.3
0.4
Bottle number
Attr
ibut
e m
ean
scor
e
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
0
1
2
3
4
5
TCA
Oxidized
Reduced
Bottle number
Attr
ibut
e m
ean
scor
e
Attributes
Panel mean scores for a 2003 Chardonnay wine sealed with natural cork closures
4 ng/L of TCA
1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11
0
1
2
3
Attr
ibut
e m
ean
scor
ePanel mean scores for a 2004 Shiraz wine sealed with screw cap and cork closures
12
Screw cap sealed bottles Cork sealed bottles
Oxidized
TCA
Reduced
Attributes
Impact of closure type and ascorbic acid addition on oxidized score after 3 years
Ascorbic acid at
bottling: added not added
7
0
1
2
3
4
5
6
Oxi
dise
d ar
oma
scor
e
Chardonnay
LSD
Screw cap
SyntheticCork 2Cork 1
Riesling
LSD
Screw cap
SyntheticCork 2Cork 1
Skouroumounis et al (2005) Aust. J. Grape Wine Res, 11, 355-368 &. 369-377.
Impact of closure type and storage position on a Chardonnay wine aroma after 3 years
Storage position: upright inverted
oxidized flint/rubber
Screwcap
Syn.Cork2
Cork1
Screwcap
Syn.Cork2
Cork1
LSD LSD
0
1
2
3
4
5
Aro
ma
scor
e
Skouroumounis et al (2005) Aust. J. Grape Wine Res, 11, 355-368 &. 369-377.
Commercial closure trial: 2002 Semillon – different closures & times post-bottling
6 12 18 24 36 6 12 18 24 36 6 12 18 24 36 6 12 18 24 36
0.0
0.5
1.0
1.5
2.0
2.5
Oxidized
Reduced
Attributes
What Is Procork? AWRI Commercial Closure Trail Reports, 12, 18, 24 and 36 months. [http://www.procork.co
m.au/whatisprocork/ind
ex.html]
Screw cap Ref 2Ref 3
ProCorkMonths since bottling
2004 Chardonnay wine sealed with ‘membrane’ corks: 24 months post-bottling
Bottle number
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Oxidized
Reduced
Attributes
Bottles stored in an upright position for 18 months post-bottling
Impact of closure type, including glass ampoules, on wine aroma after 4 years
Riesling Chardonnayoxidized flint/rubber
0
1
2
3
Cork2
Screw cap
Aro
ma
scor
e
Cork 2
Screwcap
LSD LSD
Glass ampoule
Glass ampoule
oxidized flint/rubber
0
1
2
3
Cork 2
Screw cap
Cork 2
Screw cap
Glass ampoule
Glass ampoule
LSD LSD
Skouroumounis et al (2005) Aust. J. Grape Wine Res, 11, 355-368 &. 369-377.
Aro
ma
scor
e
Wines bottled with closures with low oxygen transmission rates (OTRs) are
more likely to develop reductive character in bottle, if
those wines have
a propensity to become reductive
It is therefore incorrect to say that low OTR closures CAUSE reductive
character
•
Oxygen at bottling is consumed within weeks
•
Reductive characters, probably thiols, are formed over months or years
Oxygen to oxidize the thiols is that permeating through the closure
Increasing the headspace volume is oxygen at the “wrong” time
Fermentation management
•
Problem or stressed fermentations are more likely to contain higher concentrations of thiols and their precursors.
•
These wines will cause greater problems with post-bottling reduction
•
Yeast strain
Fermentation management
•
Better yeast preparation, particularly during re- hydration, and aeration of the culture
•
Avoid temperature shock
•
Add air and nitrogen one third of the way through fermentation
After fermentation
•
Know what the sulfur compounds are before aerating wine after fermentation -
copper
cadmium test
•
Add copper if necessary, but be aware that copper can impact on longevity as it is a catalyst for oxidation
Acknowledgements
•
Peter Godden, Dr Elizabeth Waters, Dr George Skouroumounis, Dr Alan Pollnitz, Tracey Siebert, Mariola Kwiatkowski
•
The AWRI Industry Services Team: Con Simos, Geoff Cowey, Matthew Holdstock, Emma Kennedy and Sarah Ballantine
•
All the AWRI staff who have been involved with the closure trials, especially the Analytical Service, and members of the sensory panel
•
All the other individuals and companies who have assisted with the studies
•
This work was financially supported by Australia's grapegrowers and winemakers through their investment body the Grape and Wine Research and Development Corporation, with matching funds from the Australian Government