Post on 15-Dec-2015
Premature ageing of wine aromas
Denis Dubourdieu and Valérie Lavigne,
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2005 2006 2007 2008 2009 2010
# CI
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Sources : google, private blog and web site (R.Parker, J.Robinson)
Premox or not Premox
That is the quest
ionWhen Premox phenomenon When Premox phenomenon
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Estimation
Manifestations of defective aromatic ageing in dry white wines
• loss of fruity aromas • appearance of heavier aromatic nuances reminiscent of wax polish or wax • colour with shades of yellow associated
with bitterness on the aftertaste
Olfactometric detection(C-P-G)
Comparison of aromagrams obtained from honey extracts and ones from white wine
containing honey
Aromagrams of honey extracts and of white wine containing honey
Sensory descriptors
Retention time Organic extract Organic extract(min.) from honey from wine
grapefruit, lemon
10.34 strawberry13.25 overripe pineapple 14.5 hydrocarbons15.53 herbaceous herbaceous, forest floor 18.18 burnt meat 19.15 tobacco, cigar19.53 cep 22.22 mushroom22.36 vinegar 22.5526.37 orange32.43 bitter almond bitter almond32.53 candied fruit38.17 peaches in syrup 44.02 apricot 47.44 rose rose
50.17 honey honey53.5 resin resin54.22 mothballs mothballs60.2 beeswax beeswax62.3 vanilla vanilla
ZO1
ZO2
Main molecules involved in the "defective" ageing of white wines.
Aromatic markers for defective ageing of dry white wines
NH2
CH3
O
o-aminoacetophenoneMoth balls, wax polish
0.7 µg/L
O PhenylacetaldehydeWilted roses, honey
25 µg/L
OMethional Boiled potatoes
0.5 µg/L
SMethionine(Ferreira et al., 2002)
Phenylalanine(Ferreira et al., 2002)
Carbonyl compounds O2
Indolacetic acidOxidation
These molecules cannot alone explain aromatic defects during ageing because certain prematurely
aged wines do not contain them.
Contribution of sotolon to the oxidised aroma of wine
3-hydroxy-4.5-dimethyl-2(5H)-furanone
vins jaunes from the Jura and Sherry (Guichard et al., 1993)
fig and rancio aromas of vins doux naturels (Cutzach, 1999)
walnut aromas of old Port (Ferreira, 2003)
aromas of defective ageing in dry white wines (Lavigne, 2002)
Perception threshold of the racemic mixture 7 µg/L
(Curry, walnuts)
O HCH3
CH 3O
O
*
Organoleptic characteristics of sotolon
Sotolon: a chiral molecule
The existence of one or several asymmetrical carbons can be responsible for attributing different olfactory characteristics to each enantiomer.
O
H3C OH
O
H
H3C
O
CH3HO
O
H
CH3
R S
Perception threshold of each enantiomer of sotolon
The S form that gives sotolon its smell and taste characteristics. . The (S)-sotolon is solely responsible for premature ageing of the aromas in dry white wines.
Perception thresholds (µg/L)
Descriptors
R 89 Walnuts, rancio
S 0.8 (Curry, walnuts)
Racemate 2 (Curry, walnuts)
Model solution
Distribution of various enantiomers of sotolon in dry white wines in bottle
0
20
40
60
80
100
Graves
80
Graves
81
PL 81
EDM 00
EDM 00
PL 73Bx 9
9Bx 9
9PL 87
PL 75
EDM 01
%
70/3030/7050/50
Racemic mixutre
Excess (S)-sotolon
Excess (S)-sotolon
The olfactory detection threshold determined from a commercial sotolon racemic mixture is insufficient to appreciate the olfactory impact of this
compound on wine.
How sotolon is formed in dry white wines.
O
C O OHO
OO
HO
H
α-ketobutyric acid Ethanal Sotolon
aldocondensation
What are the constituents of white wines likely to prevent the formation of these
compounds?
• in red wines: phenolic compounds, especially anthocyanins, protect young wine from oxidative phenomena that can detract from its aroma.
• as for white wines, not much is known about the compounds likely to play a role.
we have showed that certain sulphur peptides, in particular glutathion, can play a role
COO -
H+3N CH
CH2 COO -
CH2 CO NH CH2
CO NH CH
CH2
SH
Acide glutamique
Cystéine
Glycine
(Glu Cys Gly)
Glutathion
Glutathion in must and wine
Glutathion, a natural component of grapes
It has been shown to be present in large quantity in grapes: Cheynier et al, 1989; Liyanage et al., 1993
The accumulation mechanisms are not well-known. The nitrogenous intake of vines plays en essential role.
The relation between the levels of available nitrogen and glutathion in white wine must
Must 1 Must 2 Must 3 Must 4 Must 5 Must 6 Must 7 Must 8
62 244 76 202 224 56 187 42
12 28 17 28 25 6 22 4
Available nitrogen(mg/L)
Glutathion(mg/L)
Reactivity of glutathion
with oxygen: formation of disulphur
with quinones in the must: formation of GRP
Most of the glutathion in grapes disappears when the juice is extracted.
Reaction of adding a thiol (R-SH)to the catechin quinone
O
OH
OH
O
O H
H O
Reduced catechin
O
O
O
O
O H
H O
Oxidised catechin (quinone)
Oxidation
O
O H
O H
OH
O H
H O
SR
adduct
R-SH
Thiol (aroma, glutathion,etc.)
Examples of glutathion content in various Sauvignon Blanc and Sémillon musts
Must 1 Must 2 Must 3 Must 4 Must 5 Must 6 Must 7 Must 8
12 28 17 28 25 6 22 4Glutathion
(mg/L)
Changes in glutathion content during alcoholic fermentation
Changes in glutathion content in must during alcoholic fermentation
0
2
4
6
8
10
12
must T1 T3 T6 T9 sulphiting T20 T30
concentration of glutathion (mg/L)
Relation between levels of glutathion in must and in young wine
Glutathion in must (mg/L)
Glutathion in the corresponding wine (mg/L)
9 5 4 17 2
11 7 6 22 3
Relationship between the initial glutathion content of a model medium and the level at
the end of alcoholic fermentation.
0
5
10
15
20
25
30
Level of glutathion in the medium before AF Level of glutathion in the medium after AF
Con
cent
rat i
on o
f gl
utat
hion
(m
g/L
)
Relationship between the level of available nitrogen and the level of glutathion at the end
of alcoholic fermentation.
0
5
10
15
20
25
48 96 190
T0
End of AF
Concentration of glutathion (mg/L)
Level of available nitrogen in the model medium (mg/L)
Signs of premature ageing of aromas in white wines
During ageing
Traditional ageing on the lees
Protection of the young wine's fruity aromas
Maintaining wine in a state of oxidation-reduction to encourage the appearance of a bouquet showing signs of reduction: truffle, burnt and mineral nuances .
Avoids or delays manifestations of aromatic ageing
Influence of ageing techniques on the defective ageing of wine
Ageing with or without the lees
New or used barrels
Evolution - of the fruity aroma - of defective ageing markers - of glutathion
Changes in the level of 3-MH in a Sauvignon Blanc wine aged different ways in barrel
0
200
400
600
800
1000
1200
1400
1600
UsedBarrel
Used barrelracked
Usedbarrel
New barrelracked
End of AFNovemberApril
Concentration of 3-M (ng/L)
Amount of sotolon in the wines at the end of barrel ageing
0123456789
Barrelused
on the lees
Used barrelwithout lees
Barrelnew
on the lees
New barrelwithout lees
Concentration of sotolon (µg/L)
Detection threshold (white wine)
Effect of barrel ageing techniques on changes in the glutathion level of wines
0
2
4
6
8
10
12
14
16
18
concentration of glutathion (mg/L)
End of AF December January February May Samples
new barrel on the lees
new barrel without lees
used barrel on the lees
used barrel without the lees
Glutathion, sotolon and 3-mercapto-hexanol at the end of barrel ageing
Used barrel on the lees
New barrel without the lees
Glutathion Sotolon 3-MH
5.8
0.5
1.3
9.7
1400
420
(mg/L) (µg/L) (ng/L)
Glutathion, a natural component of grapes makes it possible to prevent the defective ageing of white wines.
The same ageing conditions most conducive to preserving the aromatic characteristics of dry white wines also
limit a decrease in the level of glutathion.
Interpretation of the protective role of lees with regard to defective aromatic ageing
-Release of reductive compounds - Oxygen fixation by the lees
Oxygen consumption (µg/L/h) of a white wine aged for 6 months entirely its lees
(Fornairon et al., 1999)
Wine aged on its lees 611
Filtered wine
0.01
Lees alone 542
Heat-treated lees 19
Manifestation of premature ageing once the wine is bottled
Identification of the random nature of premature ageing in two dry white wines
(tasting in 2005 of 12 bottles of each wine)
010203040506070
%
Little or no signs of age Showing average signs of ageLooking very aged
010203040506070
%
Little or no signs of ageShowing average signs of ageLooking very aged
Graves 2001
1997 Pessac Léognan
Correlation between the oxygen dissolved in bottled wines and prematurely-aged
aromas
Importance of oxidative-type reactions throughout bottle ageing
Analyses of 20 samples of a Graves white wine (1997 vintage) after 7 years in bottle.
R2 0.7084
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0 20 40 60 80 100 120 140
Dissolved oxygen (µg/l)
Average
Effect of dissolved oxygen content on colour
= 0.8315
0
0.1
0.2
0.3
0.4
0 10 20 30 40 50 60 70 80 90
DO
42
0 n
m
Level of dissolved oxygen (µg/l)
R2
R2
= 0.7909
0
5
10
15
20
25
0 20 40 60 80 100 120 140
Level of dissolved O2 (µg/l)
Free S
O2
(mg
/l)
Correlation between free SO2 and dissolved oxygen
Choice of closure…
R2 = 0.7191
0
0.5
1
1.5
2
2.5
3
3.5
0 20 40 60 80 100 120 140
Dissolved oxygen in bottle (µg/l)
Concentration of sotolon (µg/L)
0
20
40
60
80
100
120
3
Lev
el o
f ox
ygen
(µ
g/l)
1 2 4
Dissolved oxygen measured in white wine six months after bottling Effect of closure…
5
Types of closure used
15
20
25
30
Types of closure used
Fre
e S
O2
(mg/
l)
31 2 4 5
Changes in the level of free SO2 in bottleEffect of closure…
To prevent the defective ageing of white wines, IT IS NECESSARY TO
• have vines with sufficient vigour • limit the extraction of phenolic compounds during pressing • protect both the must and the wine from oxidation • make sure that alcoholic fermentation is completely finished • reduce the lag period for malolactic fermentation • age the wines in reductive conditions• limit the dissolution of oxygen when preparing the wine for
bottling • choose a closure that is suited to the wine