Presentation on theme: "Premature ageing of wine aromas Denis Dubourdieu and Valérie Lavigne,"— Presentation transcript:
Premature ageing of wine aromas Denis Dubourdieu and Valérie Lavigne,
Sources : google, private blog and web site (R.Parker, J.Robinson) Premox or not Premox That is the question When Premox phenomenon shake the web 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 timeOrganic extract (min.)from honey from wine grapefruit, lemon 10.34strawberry 13.25overripe pineapple 14.5hydrocarbons 15.53herbaceousherbaceous, forest floor 18.18burnt meat 19.15tobacco, cigar 19.53cep 22.22mushroom 22.36vinegar orange 32.43bitter almond 32.53candied fruit 38.17peaches in syrup 44.02apricot 47.44rose honey 53.5resin 54.22mothballs 60.2 beeswax 62.3vanilla ZO1 ZO2
Main molecules involved in the "defective" ageing of white wines.
Aromatic markers for defective ageing of dry white wines NH 2 CH 3 O o-aminoacetophenone Moth balls, wax polish 0.7 µg/L O Phenylacetaldehyde Wilted roses, honey 25 µg/L O Methional Boiled potatoes 0.5 µg/L S Methionine (Ferreira et al., 2002) Phenylalanine (Ferreira et al., 2002) Carbonyl compounds O2 Indolacetic acid Oxidation
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) OHCH 3 CH 3 O 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 H 3 COH O H H 3 C O CH 3 HO O H CH 3 RS
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 Graves 80Graves 81 PL 81 EDM 00 PL 73 Bx 99 PL 87 PL 75 EDM 01 % 70/3030/7050/50 Racemic mixutre 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 COOH O O O 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 + 3 N CH CH 2 COO - CH 2 CO NH CH 2 CO NH CH CH 2 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 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 O OH HO Reduced catechin O O O O OH HO Oxidised catechin (quinone) Oxidation O OH OH OH OH HO S R 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 Glutathion (mg/L)
Changes in glutathion content during alcoholic fermentation
Changes in glutathion content in must during alcoholic fermentation mustT1T3T6T9sulphitingT20T30 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)
Relationship between the initial glutathion content of a model medium and the level at the end of alcoholic fermentation Level of glutathion in the medium before AF Level of glutathion in the medium after AF Concentration of glutathion (mg/L)
Relationship between the level of available nitrogen and the level of glutathion at the end of alcoholic fermentation 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
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 Used Barrel Used barrel racked Used barrel New barrel racked End of AF November April Concentration of 3-M (ng/L)
Amount of sotolon in the wines at the end of barrel ageing Barrel used on the lees Used barrel without lees Barrel new on the lees New barrel without lees Concentration of sotolon (µg/L) Detection threshold (white wine)
Effect of barrel ageing techniques on changes in the glutathion level of wines concentration of glutathion (mg/L) End of AFDecemberJanuaryFebruary 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 (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) % Little or no signs of age Showing average signs of ageLooking very aged % Little or no signs of ageShowing average signs of ageLooking very aged Graves 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. R Dissolved oxygen (µg/l) Average
Effect of dissolved oxygen content on colour = DO420 nm Level of dissolved oxygen (µg/l) R 2
R 2 = Level of dissolved O2 (µg/l) Free SO 2 (mg/l) Correlation between free SO 2 and dissolved oxygen
Choice of closure… R 2 = Dissolved oxygen in bottle (µg/l) Concentration of sotolon (µg/L)
Level of oxygen (µg/l) Dissolved oxygen measured in white wine six months after bottling Effect of closure… 5 Types of closure used
Types of closure used Free SO 2 (mg/l) Changes in the level of free SO 2 in bottle Effect 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