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Atypical a ging (ATA) of white w ines

Atypical aging (ATA) is an aroma defect that can occur in young white wines and is unrelated to normal aging. This defect affects the sensory qualities of the wine, resulting in descriptors like mothballs, wet wool, and damp towel. This article discusses the practical significance of ATA, its sensory manifestations, viticultural causes, chemical pathway, and ways to prevent it. Winemakers can mitigate ATA by implementing viticultural practices and timely addition of ascorbic acid. By understanding and addressing ATA, winemakers can ensure the quality of their white wines.

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Atypical a ging (ATA) of white w ines

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  1. Atypicalaging (ATA) ofwhitewines Atypicalagingis an aromadefectthatmayoccur in ratheryoungwhitewinesandis not necessarilyrelatedtoaging.

  2. The practicalsignificanceof ATA • ATA is a whitewineflavordefectwidelyspread in all winegrowing countries. • Itisdistinctfromotherkindsofwhitewineaging (oxidative aging, petrolflavor, post-bottlingreductionflavor….) in bothsensoryandchemicalterms. • The attentionpaidto ATA byproducersandconsumersis variable anddoes not necessarilyreflectthefrequencyofits real occurrencein a givenwine-growingarea. • In some countries, itis not assumedtobe a distinctivewine fault. • Bysomewinecritics, itisevenconsideredas an intrinsicexpressionofterroir. • Bymanyenologists, itisconsideredthemostintractableproblemin whitewinemaking in modern times.

  3. Howdoes ATA showup in sensoryterms? Bysmell: Descriptors, group I:Descriptors, group II: - mothballs - damptowel - naphthalene- wetwool - floorpolish - dirtydish rag - acaciablossom - washingmachine - lemonblossom - urinedeposits - soap - detergentpowder - jasmine - dry linen On thepalate: • meager, thin, novolume • metallic bitterness • someastringency • light color sensorytransitiontoreductionflavor (sensoryconfusion) In all winesaffectedby ATA, thefruity, floral, ormineralvarietalaromahasdisappearedto a large extent.

  4. Viticulturalcausesof ATA soilnutrientdeficiencies greencover drought UV-radiation over-cropping earlyharvest poorphysiologicalripeness (not necessarilycorrelatedtoBrix) lack of positive aromacompounds lack ofyeast-assimilableN variable contentsofgrape-derived indole-3-acetic acid lack of O2 -radicalscavengers alc. fermentation increasedproductionofyeast-derived indole-3-acetic acid (fromtryptophane)

  5. Chemical pathwayof ATA formation O2- O2-- HO2- 2-aminoacetophenone (AAP) isthemainimpactcompoundofatypicalaging: Indole-3-acetic acid (IAA) istheprecursorof AAP: indole-3-acetic acid (IAA) 3-methyl-indole(skatole) 2-aminoacetophenone (AAP) oxygenradicals (mothballs, soap, detergentpowder, acaciablossom, dry linen) (odorless) SO2 + O2 1. The conversionof IAA into AAP isinitiatedbyoxygenradicalsgeneratedwhen SO2isaddedthefirst time postfermentation. 2. Itrequiresonlyminuteamountsofdissolvedoxygen (< 0.5 mg/L) andis not relatedto oxidative aging. 3. Redwines do not produce AAP becausetheir total phenols (~ 2000 mg/L) scavengeoxygenradicalsin contrasttowhitewines….displayingonly ~ 200 mg/L total phenols.

  6. Viticulturalmeanstoprevent ATA(Central European cool-climateconditions) Startingpoint: - ATA isa viticulturalproblemresultingfrom a physiological stress in thevines. - White winesproducedfromstressedfruitdisplayhigherconcentrationsoftheodorlessprecursor (IAA) … andlowerconcentrationsofoxygenradicalscavengers. Counter-measures in thevineyard: • Makesurewatersupply / irrigationaroundvéraison (July/August) • Reducegreencover • Makesureenoughorganic matter in thesoil (> 2.5 % humus) • Adjustnitrogensupplytoapproximately 60 kg/ha N • Reduceyield, avoidovercropping • Allowforfullphysiologicalripeness (transparent skinseasilyto separate fromthepulp)

  7. Enologicalmeanstoprevent ATA Timelyadditionofascorbicacidistheonlyreliablewaytoprevent ATA in winespronetodevelop it. Sincethefirstadditionof SO2 after fermentationinitiatesthereactionleadingto ATA, ascorbicacid (15 g/hl) shouldbeaddedsimultaneouslyor a fewdays after. Itstalls ATA formationwhenadded at a laterpointof time. The reactionleadingto ATA is irreversible. Ascorbicacidnoranyothertreatmentcannotremove ATA alreadydeveloped.

  8. Impact ofaromaintensityof 38 whitewines(Germany 2011 + 2012) upon theolfactoryperceptionof AAP AAP detectionthresholdisaround 0.5 µg/L, AAP rejectionthresholdis 1.0 µg/L approximately, depending on thewinematrix. The strongerthewinearoma, thelessperceptibleis AAP due tomaskingeffects.

  9. Testing a winefor ATA potential(acceleratedagingtest) Take a wine sample (200 mL min.) Add SO2ifnecessary (~ 70 mg/L) Clarify bycentrifugationorfiltration Store bothflasks at 50-60° C (incubator) during 3-4 days. Cool down toambienttemperature. Identify ATA byolfactorycomparisonofbothflasks. Ifthe sample withoutascorbicaciddisplays ATA (orifthe sample withascorbicacidsmellsbetter), thewineispronetoproduce ATA andshouldbetreatedimmediately. Sample I: 100 ml-flaskwithscrewcap, with 15 g/hl ascorbicacid Sample II: 100 ml-flaskwithscrewcap, withoutascorbicacid

  10. Special requirementsforwinessupplementedwithascorbicacid

  11. Conclusion: Itis not a shametohave a wineaffectedby ATA, but it‘sdisgracefultohaveityear after yearwithouttaking counter-measures. Forfurtherinformations: Volker Schneider Email: Schneider.Oenologie@gmail.com www.Schneider-Oenologie.com

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