Premature ageing of wine aromas

Denis Dubourdieu and Valérie Lavigne,

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Sources : google, private blog and web site (R.Parker, J.Robinson)

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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

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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

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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.

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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.

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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

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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

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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

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6.00

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Dissolved oxygen (µg/l)

Average

Effect of dissolved oxygen content on colour

= 0.8315

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0.2

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0.4

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DO

42

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m

Level of dissolved oxygen (µg/l)

R2

R2

= 0.7909

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Level of dissolved O2 (µg/l)

Free S

O2

(mg

/l)

Correlation between free SO2 and dissolved oxygen

Choice of closure…

R2 = 0.7191

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1.5

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2.5

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3.5

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Dissolved oxygen in bottle (µg/l)

Concentration of sotolon (µg/L)

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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

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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