4Manifestations of defective aromatic ageing in dry white winesloss of fruity aromasappearance of heavier aromatic nuancesreminiscent of wax polish or waxcolour with shades of yellow associated with bitterness on the aftertaste
6Comparison of aromagrams obtained from honey extracts and ones from white wine containing honey
7Aromagrams of honey extracts and of white wine containing honey Sensory descriptorsRetention timeOrganic extractOrganic extract(min.)fromhoneyfromwine10.34strawberry13.25overripe pineapple14.5hydrocarbons15.53herbaceousherbaceous, forest floor18.18burnt meat19.15tobacco, cigar19.53cep22.22mushroom22.36vinegargrapefruit, lemon22.5526.37orange32.43bitter almondbitter almond32.53candied fruit38.17peaches in syrup44.02apricot47.44roseroseZO1ZO250.17honeyhoney53.5resinresin54.22mothballsmothballs60.2beeswaxbeeswax62.3vanillavanilla
8Main molecules involved in the "defective" ageing of white wines.
9Aromatic markers for defective ageing of dry white wines MethionalBoiled potatoes0.5 µg/LSMethionine(Ferreira et al., 2002)Carbonyl compoundsO2OPhenylacetaldehydeWilted roses, honey25 µg/LPhenylalanine(Ferreira et al., 2002)NH2C3Oo-aminoacetophenoneMoth balls, wax polish0.7 µg/LIndolacetic acidOxidation
10These molecules cannot alone explain aromatic defects during ageing because certain prematurelyaged wines do not contain them.
11Contribution of sotolon to the oxidised aroma of wine 3*3-hydroxy-4.5-dimethyl-2(5H)-furanone(Curry, walnuts)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
13Sotolon: a chiral molecule 3OH3CRSThe existence of one or several asymmetrical carbons can be responsible for attributing different olfactory characteristics to each enantiomer.
14Perception threshold of each enantiomer of sotolon Perception thresholds (µg/L)DescriptorsR89Walnuts, rancioS0.8(Curry, walnuts)Racemate2Model solutionThe 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.
15Distribution of various enantiomers of sotolon in dry white wines in bottle 50/5030/7070/30Racemic mixutre10080Excess (S)-sotolon60%Excess (S)-sotolon4020PL 81PL 73EDM 00EDM 00Bx 99Bx 99PL 87PL 75Graves 80Graves 81EDM 01The olfactory detection threshold determined from a commercial sotolon racemic mixture is insufficient to appreciate the olfactory impact of this compound on wine.
16How sotolon is formed in dry white wines. aldocondensationCOOHHOOOα-ketobutyric acidEthanalSotolon
17What are the constituents of white wines likely to prevent the formation of these compounds?
18in red wines: phenolic compounds, especially anthocyanins, protect young winefrom oxidative phenomena that can detract from its aroma.as for white wines, not much is knownabout the compounds likely to play a role.we have showed that certain sulphur peptides,in particular glutathion, can play a role
21Glutathion, a natural component of grapes It has been shown to be present in large quantityin grapes: Cheynier et al, 1989; Liyanage et al., 1993The accumulation mechanisms are not well-known.The nitrogenous intake of vines plays en essential role.
22The 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 8Available nitrogen(mg/L)Glutathion
23Reactivity of glutathion with oxygen: formation of disulphurwith quinones in the must: formation of GRPMost of the glutathion in grapesdisappears when the juice is extracted.
24Reaction of adding a thiol (R-SH) to the catechin quinone OHOOHOxidationHOOHOOOOOHOHOxidised catechin (quinone)Reduced catechinR-SHThiol(aroma, glutathion,etc.)OHOHHOOSOHROHadduct
25Examples 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 8Glutathion(mg/L)
26Changes in glutathion content during alcoholic fermentation
27Changes in glutathion content in must during alcoholic fermentation concentration of glutathion (mg/L)24681012mustT1T3T6T9sulphitingT20T30
28Relation between levels of glutathion in must and in young wine Glutathion in must(mg/L)Glutathion in the corresponding wine
29Relationship between the initial glutathion content of a model medium and the level at the end of alcoholic fermentation.51015202530Concentration of glutathion (mg/L)Level of glutathion in the medium before AFLevel of glutathion in the medium after AF
30Relationship between the level of available nitrogen and the level of glutathion at the end of alcoholic fermentation.Concentration of glutathion (mg/L)252015T010End of AF54896190Level of available nitrogen in the model medium(mg/L)
31Signs of premature ageing of aromas in white wines
33Traditional ageing on the lees Protection of the young wine's fruity aromasMaintaining wine in a state of oxidation-reductionto encourage the appearance of a bouquet showing signsof reduction: truffle, burnt and mineral nuances .Avoids or delays manifestations of aromatic ageing
34Influence of ageing techniques on the defective ageing of wine Ageing with or without the leesNew or used barrelsEvolution - of the fruity aroma- of defective ageing markers- of glutathion
35Concentration of 3-M (ng/L) Changes in the level of 3-MH in a Sauvignon Blanc wine aged different ways in barrelConcentration of 3-M (ng/L)2004006008001000120014001600End of AFNovemberAprilUsedBarrelUsed barrelUsedbarrelNew barrelrackedracked
36Amount of sotolon in the wines at the end of barrel ageing Concentration of sotolon (µg/L)123456789Detection threshold(white wine)BarrelUsed barrelBarrelNew barrelusedon the leeswithout leesnewon the leeswithout lees
37Effect of barrel ageing techniques on changes in the glutathion level of wines concentration of glutathion (mg/L)24681012141618new barrel on the leesnew barrel without leesused barrel on the leesused barrel without the leesSamplesEnd of AFDecemberJanuaryFebruaryMay
38Glutathion, sotolon and 3-mercapto-hexanol at the end of barrel ageing Glutathion, a natural component of grapesmakes it possible to prevent the defective ageing of white wines.Used barrel on the leesNew barrel without the leesGlutathion Sotolon MH126.96.36.199.71400420(mg/L)(µg/L)(ng/L)The same ageing conditions most conducive to preservingthe aromatic characteristics of dry white wines alsolimit a decrease in the level of glutathion.
39Interpretation of the protective role of lees with regard to defective aromatic ageingRelease of reductive compoundsOxygen fixation by the lees
40Oxygen consumption (µg/L/h) of a white wine aged for 6 months entirely its lees Wine aged on its lees611Filtered wine0.01Lees alone542Heat-treated lees19(Fornairon et al., 1999)
41Manifestation of premature ageing once the wine is bottled
42Identification of the random nature of premature ageing in two dry white wines (tasting in 2005 of 12 bottles of each wine)7060Graves 200150%40302010Little or no signs of ageShowing average signs of ageLooking very aged701997 Pessac Léognan605040%302010Little or no signs of ageShowing average signs of ageLooking very aged
43Importance of oxidative-type reactions throughout bottle ageing Correlation between the oxygen dissolved in bottled wines and prematurely-aged aromasAnalyses of 20 samples of a Graves white wine (1997 vintage) after 7 years in bottle.Average6.00R20.70845.004.003.002.001.000.0020406080100120140Dissolved oxygen (µg/l)Importance of oxidative-type reactions throughout bottle ageing
44Effect of dissolved oxygen content on colour 2R=0.40.3DO420 nm0.20.1102030405060708090Level of dissolved oxygen (µg/l)
45Correlation between free SO2 and dissolved oxygen 252015Free SO2 (mg/l)2R=10520406080100120140Level of dissolved O2 (µg/l)
46Choice of closure… R 2 = 0.7191 Dissolved oxygen in bottle (µg/l) 0.511.52.533.520406080100120140Dissolved oxygen in bottle (µg/l)Concentration of sotolon (µg/L)
47Dissolved oxygen measured in white wine six months after bottling Effect of closure…12010080Level of oxygen (µg/l)60402012453Types of closure used
48Changes in the level of free SO2 in bottle Effect of closure…3025Free SO2 (mg/l)201512345Types of closure used
49To prevent the defective ageing of white wines, IT IS NECESSARY TO have vines with sufficient vigourlimit the extraction of phenolic compounds during pressingprotect both the must and the wine from oxidationmake sure that alcoholic fermentation is completely finishedreduce the lag period for malolactic fermentationage the wines in reductive conditionslimit the dissolution of oxygen when preparing the wine for bottlingchoose a closure that is suited to the wine