– Master’s Thesis –

AgroParisTech

Graduate Institute in Life Science and Engineering

Paris, February 2016

Wine Typicality and Vine Responses to Terroir Constraints, A Review

Supervisor: Author:SylvainChaillou RomainLebrun

Seule,danslerègnevégétal,lavignenousrend intelligible ce qu’est la véritablesaveurdelaterre.1

ColettePrisonsetparadis,1932

1Alone,intheplantkingdom,thevinemakesintelligiblethatwhichisthetrueflavouroftheearth.

AcknowledgmentsTheimpetusbehindthisreviewcamefromapropositionofAnselmeSelosseaboutthenotionof terroir and,more generally, about the relationshipbetween an agricultural product and itsplaceoforigin.IdeeplywanttothankM.Selosseforthisopportunityaswellasforhiscollaboration,thewealthofourdiscussions,andhisoutstandinglovetosharehisknowledge.Many thanksalso to JordiBallester (BurgundyUniversity,France),EmmanuelBourguignon(Laboratoired’AnalysesMicrobiologiquesdesSols,France),DavidLefebvre(œnologist),Keesvan Leeuwen and Jean-Philippe Roby (Bordeaux Sciences Agro, France), EmmanuelleVaudour (AgroParsTech, France), Alain Deloire (Charles Sturt University, Wagga Wagga,Australia) andWendy V. Parr (LincolnUniversity, New-Zealand) for their involvement, theiravailabilityandtherelevantinformationtheyagreedtoshare.Withoutthem,thisreviewwouldnothavebeenpossible.I finally want to thank Sylvain Chaillou (AgroParisTech, France) for his consistent helpthroughoutthecourseofthisstudyaswellasIsaacEkbladforhisgreathelpintranslatingthisdocumentinEnglish.

AbstractTerroirhasbeenlargelystudiedinvineandwinesciencesforthepurposeofunderstandinghowinteractionsbetweensoil, climateandmicrobiotaaffectaplant.Thisstudyreviews the terroireffectonvinephysiologyandgrapechemistryandshedslightonthepossibleconsequencesonwinetypicality.Theterroirexpressionisoptimalwhenvineprecocitymatcheswithlocalclimaticconditionsandwhenyieldandvigourare limited throughwaterdeficit stressor lownitrogenavailability. However, even if environmental factors do affect the composition of vines andgrapes,thereisnoscientificargumentthatprovesaterroireffectthroughanysensorymarkerinwine so far. Recently, promising studies have shown interesting results that bondmicrobiologicalandmineralfootprinttotasteandscentinwine.Furtherresearchisnecessarytocorrelateterroireffecttowinetypicality.

KeywordsTerroir,terroireffect,winetypicality,minerality

TableofContents

Introduction...........................................................................................................................................................................11 Terroirgeneralities.....................................................................................................................................................21.1 Backgroundanddefinitions...........................................................................................................................21.2 Socioculturalaspects.........................................................................................................................................31.3 Maincomponentsandchallengesconcerningterroir........................................................................4

2 Influence of geo-pedoclimatic terroir components on the grape’s physico-chemical

properties................................................................................................................................................................................62.1 Indirectinfluencesofgeology.......................................................................................................................62.2 Climate-vineinteraction,theprominenceofprecocityandwatersupply................................72.2.1 Precocity,temperatureandsunshinerate.....................................................................................72.2.2 Moderatewaterdeficiencyandberriesquality...........................................................................8

2.3 Thesoil-vineinteraction,importanceoftexture,structureandsoilcomposition................82.3.1 Physicalpropertiesandsoilporosity...............................................................................................92.3.2 Mineralcompositionofsoil,vinedevelopmentandberriesmaturity............................10

3 Evolutionofthenativemicrobialpopulationsdependingontheterroir........................................133.1 Placedependantcommunities...................................................................................................................133.2 Thecultivardependantstrains..................................................................................................................143.3 Microbiota-vineinteractionanditsinfluencesonberrycomposition.....................................153.3.1 Therhizosphereinfluence..................................................................................................................153.3.2 Phyllosphereinfluence.........................................................................................................................163.3.3 Consequences on the berry composition and the fermentation potential

ofthemust...............................................................................................................................................................164 Perceptionofwinetypicality...............................................................................................................................184.1 87Sr/86Srisotopepair,apedologicalmarker.......................................................................................184.2 Thevolatilescompounds,olfactorycompounds...............................................................................184.3 Thetasteofterroir:minerality?................................................................................................................20

Conclusion...........................................................................................................................................................................24Bibliography.......................................................................................................................................................................25

IllustrationsTable

Figure1:SchematicrepresentationofthebacteriaandfungipopulationsassociatedwithvineorgansVitisvinifera(Gilbertetal.,2014)Figure2:Compared impacts relative to cations concentration (adding mineral salts) and wine taste(Vignonetal.,2012)Figure3:Compared impacts relative to anions concentration (adding mineral salts) and wine taste(Vignonetal.,2012)ListofAcronymsABA:AbscisicacidAOC:Appellationd’OrigineContrôlée(ControledOriginAppellation)CEC:CationicExchangeCapacityINAO:InstitutNAtionaldel’Origineetdelaqualité(NationalInstituteofOriginandQuality)INRA:InstitutNationaldelaRechercheAgronomique(NationalInstituteofAgronomyResearch)OIV:OrganismeInternationalduVin(WineInternationalOrganisation)PDO:ProtectedDesignationofOriginPGI:ProtectedGeographicIndication

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IntroductionInaworldcharacterizedbyaubiquitousstandardizationandnormalizationofgoods,immutablenaturalistsarestillmarvellingaboutthediversityoflife.Ifthediversityandtypicalityofarawproductisleftuntouchedduringatransformationprocess,thefinalproductcanbeunique,non-reproducible,andjustasdiverseasitwasinitsrawform.Whenthisdiversity isallowed inacrop, thegrowingenvironment isusually firstdivided intoterritories,andthenintoplots.Thus,thenotionofplaceappears,towhichweattachimportanceandfromwhichtheoriginalityoftheproductisobtained.Theconceptofterroirwasbornfromthenotionofplace.Today,itsubiquitousapplication isusedtovalorise theuniquenessofagivenproduct that integrates itsquality with its geographical origin and with the characteristics of the production place. Formany,terroirensuresaproduct’sso-calledauthenticity.Indeed, the word “terroir“ is a French word that comes from the latin territorium thatmeans“territory”.TheFrenchdictionaryLeRobert2011givesthefollowingdefinition:

1. Ruralarea,state,consideringasinfluencingitsinhabitants.Terroiraccent.Terroirpoets.2. Cluster of landbelonging to the same region, producing a typical agricultural product.

Tasteofterroir,inherentfromthefield.Tastecorrespondstosensorialperceptionofacidity,bitterness,sweetnessandsaltinessbythetongueandthepalate.The“tasteofterroir”isagustativeoriginality,faithfultotheproductionplace’sparticularities,anddefinedbytheuniquesensationsofacidity,bitterness,sweetnessandsaltiness.In viticulture, terroirmeans an interactive agrosystem, associatedwith a place and involvingclimate, soil and vines (van Leeuwen, 2010). An agrosystem is a biocenosis (non-biologicalenvironmental component) composed of vines, which develops in a biotope (habitat) and isborderedbyculturalpractices.Despiteitscommonuse,theunderstandingoftheconceptofterroirremainscomplexbecauseitis composed ofmany factors. Considering the association of the vine and itsmicrobiota as abiologicalsystem,thisreviewaimstodescribetheresponsesofthisbiosystemcomparedtotheconstraintsdefinedby theenvironmental andanthropogenic factors, all these factorsdefiningtheterroir.Moreover, the response of the “vine-microbiota” system induces unique wine characteristics,dependingonthevintage,theplace,andtheculturalandoenologicalmethods.Theobjectiveistoaddresshowthisuniquenesscanbeperceivedinthetasteofwine.Thisreflectionconcludesbyevaluatingthepurportedlinkbetweenthebiosystemresponseandthewine’sgustativeparticularities.Afterdetailingtheinteractionsbetweentheterroirandthegrapes, a final chapter will focus son the existence of markers testifying to the organolepticexistenceoftheterroireffect.

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1 Terroirgeneralities

1.1 BackgroundanddefinitionsThe notion of terroir was originally developed in Burgundy, France in order to identify anddefine territories deliveringwines of different natures. In this context the appellations “crus”,clos”(smallbatchorsession)andalso“climats”(climate)wereborn.Nowadays, it is easily confused with the appellations defined by the characteristics of theproduction place and the numerous European certification labels such as PDO “ProtectedDesignationofOrigin”orPGI“ProtectedGeographicIndicaction”(Vaudouretal.,2015).InFrance, ItalyandSpain,wine territoriesareprotected thanks toPDO, called inFranceAOC“Appellation d’Origine Contrôlée” for “Controlled Origin Appellation”, to which the FrenchNationInstituteofOriginandQuality(INAO)givesthefollowingdefinition:

The AOC in a French sign that designates a production wherein the authenticity andtypicality are related to its geographic origin. This is the expression of the intimate linkbetweentheproductanditsterroir:ageographicarea(geologic,agronomic,climaticandhistorical characteristics), human artwork and specific production conditions to get thebest of the nature. Natural and human factors are bounded together. The given productcannotbereproducedoutsideitsoriginalterroir.

Interestingly, therehasbeenan extrapolationof thenotionof terroir inother crops and foodproducts such as coffee (de Assis Silva et al., 2014), tea (Besky, 2014), tequila (Bowen andZapata,2009), andalsohoney,maple syrup, chocolate, oliveoil, various fruits andvegetables,and some cheeses (Jacobsen, 2010; Trubek, 2008). The marketing of these products makesclaimsabouttheirindividualityandtheparticularityoftheirproductionplace.

Forthesereasons,itisessentialtodefinethenotionofterroiraswellasitscomponents.The scientific community seems to agree that the notion of terroir describes a delicateequilibrium resulting from the interactions between the natural terroir components (climate,soilandcultivar)andthefarmingandoenologicaltechnics(vanLeeuwenandSeguin,2006;vanLeeuwenetal.,2004).Fromtheperspectiveofthetaster,theconceptofterroircanbesummedupastherelationshipbetween the wine’s sensory characteristics and the environmental conditions in which thegrapeshavebeengrown(vanLeeuwenandSeguin,2006).The expert group from the Wine International Organisation (OIV) also gives its own terroirdefinition.Theysaythatterroirisa,

Geographic area delineated where a human community builds, along his history, acollective production know-how based on an interactive system between physical andbiological environment as well as a set of human factors. The socio-technical routesinvolved,revealoriginality,confertypicalityandleadtoareputation,foragoodfromthisgeographicarea(Casabiancaetal.2006).

According to these experts, terroir therefore confers typicality, and yet, Casabianca (2006)defines “typicality” as, “a characteristic belonging to a type, distinguished and identified by ahumanreferencegroup.”

This definition tends to restrict typicality to category, insofar as it consolidates like productstogetherandtherebyoversimplifies.

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Effectively, products from the same terroir can be authenticated thanks to commonmarkers;namely,certainspecificities.Ideally,whiletasting,thefamiliarconsumerwouldbethusabletorecall similar mental images that correspond to the flavors he recognizes and allow him toidentifyaproducttoitsoriginandtoitsterroir.Thesavvyconsumerlooksfortheproductsingularityandtheoriginalitythatallowhimtocatchthe changes among products exhibiting terroir. It is this singularity, constantly changingaccordingtotheplaceandthevintage,whichisthewitnessofthevariabilityoflifeandwarrantsthenon-reproducibilityoftheproduct.Thus, for therestof thestudy, thedefinitionof typicality in relation to terroirwillbe theonegivenbySauvageot(1994).Forthisauthor,aproductexhibitingtypicalitycorrespondsto: -Characteristic(Sign,trait,characteristicdifference)

- Specific (1.Thatbelongsexclusively toakind.Specificquality.2.Accurate,determined.3.Hasacharacterspecies)

- Original(1.Whichhasanoriginalcharacter,primitive.2.Whichseemsinvented, imaginedorwithoutpreviousmodelmemory.3.Whichismarkedwithitsownfootprint)

-Singular(1.Whichbelongstoone.2.Whichisnotliketheothers.3.Rareexcellence)

Finally,inthe“terroir”definitionfromOIV,specialimportanceisassignedtothehumanfactor.Indeed, in addition to the scientific and technical dimensions, terroir involves an identity, asignificantsocioculturaldimensiongiventoitbyhumanbeings.

1.2 SocioculturalaspectsWhentalkingaboutthedefinitionofterroir,itisessentialtokeepinmindthatisaconceptthatreferstoacollectiveknowledge,definednotbyaresultbutbyaproductionprocess(Teil,2011).AccordingtoWarenMoran,professoratMoranUniversity,Auckland,New-Zealand,

Terroir is a social construction,wherein environmental effects on thewine typicality aredetected,determined,maximisedandfinallytradedbythesamepersonwhodecidedthatitwasactuallypresent.Theexistenceofterroir itself isproducedbypeoplewhointerpret itandfititintotheirpurposes.(P.Comiskey,2006).

In thisway, terroirdoesnotexistwithoutproduction techniquessetby thewinemakerand itcannotbedefinedwithoutthewinemakingprocessthatinsureitsexpression.Thus,thewinemakerplaysanessentialroleasarevealer.(Teil,2011).Thisrevealerroleneedspersonalreflectionabouttheinterpretationandthebestwaytorevealtheterroirexpressionbymeansoftechnicalchoices.Inotherwords,therevealerneedstothinkabouttheidentitythathewantstogivetohisproduct.Will itbeclosetotheproduct’smostrawexpressionorwill itbecustomizedandmarketed?Considering thedynamismof this reflection, thehuman componenthas a significant effect onthesingularityofthefinalproduct.Looking at terroir as a human production, it is also associated with the will of socialdifferentiationthatcanbecomearealmarketingargumentwhensellingtheproduct.

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Man is the only taster of the product that expresses terroir. His perception is incrediblysubjective, dynamic, and variable. The human component does not contribute only to thesingularityoftheterroirexpressionbutalsotothesingularityofitsperception.Thus,thehumanfactorcorrespondstoanessentialcomponentwithinthedefinitionofterroir,both involved in the stresses applied to the biological system as well as in assessing thetypicalityofthewine.This dynamic involvement between man and terroir breathes subjectivity and life into theproduct and with this subjectivity comes a distinct sensorial vantage point that is revealedduringitsassessment.

1.3 MaincomponentsandchallengesconcerningterroirBecauseofthelargenumberoffactorsinvolvedindefiningterroir,wesometimesobserveawilltosimplifyortohierarchizethecomponents.Thesedifferencesofpointofviewabouthierarchiescomposedofdifferentterroircomponentscanexistaccordingtothescale.Indeed,onacountryorabigregionalproductionscale(macrolevel),climateisthemainfactorimpacting theexpressionof terroir, before soil and cultivar choice.At theopposite endof thespectrum, on amicro level, when focusing on a specific spot, the soil becomes the dominantfactor(vanLeeuwen,2010).Moreover,differencesintherankofthesefactorsarecontingentonsocietaldifferences.InEurope,forinstance,moreimportanceisgiventothevineyard’slocationthantothegrapeorthewinemaker’sname.Ontheotherhand,winelabelsfromnewproducercountrieshighlightthenameofthegrapeandthe winemaker. Hence, there’s a big difference between European concepts of terroir andAmericanorSouthernHemispherecounterparts.Ifsimplifyingterroirtothecultivarchoiceandtotheoenolicaltechnics,theAnglo-Saxontheorydefendsthereproducibilityofwinesregardlessoforiginandthusdetachestheproduct’squalityfromitsplaceofproduction.Otherwise, theEuropean theorypromotes the conceptof terroir’s singularity,highlighting theplaceandgiving importancetothe linkbetweentheproductanditsoriginalregion.Thus, thislasttheoryclaimsthenon-reproducibilityofwinesboundtotheirterroir.Infact,theterroirquestionisdouble.First,asitaimstoanalysethecomponentsthatdefinethecharacteristicsoftheproductionplaceandthentounderstandtheirinteractionswiththeplant,thistopicconcernsterroirinthesenseofaproductionunit.Second,theobjectiveistoknowifthisgeographicalproductionunithasasensorialexistence.Does an organoleptic difference with a terroir related origin exist? Can we distinguish withcertitudetwoappellationsfromasameproductionareaonlybymeansoftasting?This second line of questioning is more prone to controversy as it challenges the rationalexistenceofEuropeanvineyardsappellation,thusraisingmanypoliticalandeconomicalissues.

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These questions animate the wine industry and are causing many debates about the veryexistenceof terroir, questionedby someAnglo-Saxons.This is crucialbecause it ensuresboththesustainabilityofproductionsfaithfultothevariabilityoftheresourcesfromaterroiranditwarrantsthediversityofwinesaccordingtotheirorigins.Terroir issuchacomplexnotionbecause it implementsvariouscomponentsrelating tooriginanditrequiresamultidisciplinaryapproach.Therestof thestudyconsists inemphasizing thephenomena influencinggrapequality, firstlyfocusingonthegeo-pedoclimaticfactorsandthenontheinfluencesofmicrobialpopulations.

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2 Influenceofgeo-pedoclimaticterroircomponentsonthegrape’sphysico-chemicalproperties

Theimpactofthepedoclimaticcomponentofterroironthegrape’sphysico-chimicalpropertiesissubstantialbecauseof the inductionof fruitingandvegetativephaseof thevine. Instressfulenvironmentalconditions,whenthevinestrivestogrow,thephysiologicalresponsefavorsfruitproduction.For these reasons, while producingwine, the grape’s optimal quality is reached in a delicateequilibriumbetweenvigourandmoderatedeficiency.

2.1 IndirectinfluencesofgeologyEven though there is no consensus claiming a direct influence of geology on grape quality,geomorphologyaffectsbothclimateandsoilproperties.Indeed, topography involves a temperature shift (1°C per 100m) as well as light intensitydifferencesreceivedbythevegetation.Italsoconditionssomeclimaticphenomena,suchastheFoehnphenomenonthatresultsincharacteristicmicroclimates.Furthermore, as shown in theChablisandpetitChablis vineyard, geomorphology significantlyinfluences the soil’s propertiesdependingon the sedimentary layers. In fact, thedifferenceofhardnessbetweenthesediments fromthesetwolocationsaffectstheir landscapesresulting inmoreimportantdrainingcapacitysoilonthesteepslopes;thispartlyexplainsthewinequalitydifferencebetweenthesetwoterroirs(Wilson,1998).In the same way, the slope favors sediment transport brought on by solifluction. Thus,superficial layers like clays can be transported downhill and become absent on the steepestslopes. These various sedimentary layers can be at the origin of totally distinguishing winetastesasillustratedbysomewinesmadebyDomaineJacquesSelosse.The geological sediment origin also influences the organisation and the nature of the atomsdefining minerals within rocks, resulting in rocks with various porosity, hardness andcomposition.Thissubstratevariabilitycreatesauniquesoilenvironmentforthevineandmayberesponsibleforcharacteristictastesinwine.Again, tasting thewine “Sous leMont” fromDomaine Jacques Selosse is an illustrationof thishypothesis.Thiswineismadefromvinesthatgrowonamagnesium-richlimestonesoilandithas actually a singular taste, surprisingly close to the one of Hépar water, a French wateramongsttherichestinMg.Finally, the geologicalmovements and the constraints applied to the rocksby the climate cancauseflawsanddiaclases.Thesediscontinuitiesallowdeep-waterinfiltrationandcorrespondtoerosionandoxidationareaswhereinthevinerootscanbeinstalled.In this way, geology can influence a root system environment and the availability of somemineralsforthevinenutrition.Thus,itispossiblethatthegeologyonthelandscape,aswellasthesoilandthesubsoil,influencemoreorlessdirectlythephysic-chemicalcompositionofthegrapes.

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Withouthavingscientificproof,thecloselinkthatmightexistbetweenthisgeologicaldimensionoftheterroirandthetasteofthewineremainsunsubstantiated.

2.2 Climate-vineinteraction,theprominenceofprecocityandwatersupplyInadditiontoclimaticconsequencesonerosion,sedimenttransport,andsoildevelopment,theclimatedirectly affects thephysiological responseof theplant and in the caseof thevine, thegrape’scomposition.Grapequalityisdeeplyboundtosugarconcentration,pHvalue,pigments,phenoliccompounds,and the contentof aromatic compounds.Dependingon the typeofwine that is produced, thelevel of these parameters varies. All these criteria are related to the grape’s degree ofmaturation, so the quality is dependant on the cultivar precocity, the temperature and thesunlight,thewind,theevapotranspiration,andtherain.

2.2.1 Precocity,temperatureandsunshinerateTerroir’sexpressionmainlydependsontheharmonybetweentheprecocityofthevarietyandtheclimaticconditions.Thematurityofthegrapeshastobeoptimalandafteralongtimeonthevine. Indeed,quicklyreachedmaturity limits thesynthesisofaromaticcompoundsandaffectswinequality(vanLeeuwenandSeguin,2006).Thus, early varieties such as PinotNoir, Chardonnay, or Gewurztraminer are grown in coolerareastoachieveoptimumripenessattheendoftheirgrowingseason.This correlation is related to the effect of temperature on the berry’s composition. In fact,amongst the organic compounds where the concentration increases with the raising oftemperature, there are proline, sugar (with an optimal between 25°C and 30°C) andanthocyanins (with an optimal between 17°C and 26°C) (Pirie, 1997). Some mineralconcentrationslikepotassiumalsoincreasewithtemperature(vanLeeuwen,2010).On the other end of the spectrum, low temperatures favour the development of aromaticcompounds(vanLeeuwen,2010)aswellasthesynthesisofpigmentsforblackgrapevarieties(KliewerandTorres,1972)andtheconcentrationofmalate(vanLeeuwen,2010).Other authors believe that grape composition ismore related to the sun exposure. Thus, theconcentrationsofsugar,proline,sodium,calcium(Pereiraetal.,2006;Sonetal.,2009)aswellastheaccumulationofanthocyanins(Spaydetal.2002)increasewiththeexposuretosunshinewhereastheconcentrationsofmalate,citrate,alanine,threonineandtrigonellinedecrease.It isobviousthat, insomecases, there isacorrelationbetweenthe intensityofsolarradiationand the temperature. However, as altitude increases, the temperature and the UV intensitydecrease.Thus,thebiologicalresponseoftheplantcorrespondstotheeffectsofraisingthelightintensitycoupledwithalowtemperature.Amongstthedifferencesofgrapecompositioninducedbythedegreeofmaturity,sugarcontent,anthocyanins content, and acidity are factors that significantly influence wine quality (vanLeeuwenetal.,2004). It is throughtheseparametersthatclimate influencesthequalityof theberriesand,subsequently,thewine.

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2.2.2 ModeratewaterdeficiencyandberriesqualityAnother pedoclimatic factor that affects grape quality is water potential. Mainly for theproductionofredwines,ithasbeennoticedthattheberry’squalityincreaseswhenthevineiscultivatedinmoderatewaterstressconditions(vanLeeuwen,2010).Indeed, in the case of lightwater deficiency, especially beforeveraison, the hormonal balancebetweenabscisicacid (ABA), cytokinin,gibberellinandauxinswitch forABA.Thesynthesisofthis hormone, within the root system, favors the concentration of anthocyanins and tanninsinsidethegrapes(PirieandMullins,1976).Moreover,anincreaseinthewatersupplyresultsinaturgescenteffectonthefruit, increasingtheberry’svolumeanddecreasingtheconcentrationofsugarandothercompounds,especiallyphenoliccompounds.Onceagain, theconcentrationofkeyelements in thequalityofgrapesand inwinequalityarelinkedtospecificclimaticconstraintsfromtheterroirwherethevinegrows.Theclimate-vineinteractionaffectsthetypicalityofthegrapesthroughclimaticfactorsdefiningorganic compounds concentrations such as sugar, pigments and antioxidants. Here, theprecocityofthecultivarandthevariabilityoftheclimaticconditionsensuretheuniquenessofthechemicalcompositionoftheberries.Concerningwaterpotential, the compositionand the textureof the soil play anessential role,especially regarding the capacity for water retention. The soil also largely influences thecompositionofgrapessinceitconstitutesthenutrientsubstrateandtheplant’sgrowthsupport.

2.3 Thesoil-vineinteraction,importanceoftexture,structureandsoilcomposition

Whereas numerous studies focus on the foliar surface and the ratio between berry quantity/foliarsurface,itwouldbeinterestingtoanalysetheratiobetweenberryquantity/rootexchangesurface.

This thought fromDavidLefebvre, shared in2006 in the forum lapassionduvin.com, illustratestheimportanceoftheexchangeinthesoil-rootinterface,oftenforgotteninmanystudiesandnotaswellknownastheaerialparttransfers.Inthisreviewitispreciselythelinktothegroundthatisintheheartofthequestion.Thesoil-vineinterfaceisthusthecentralaspectofthisstudy.Although it is not possible for the vine to extract aromatic compounds from the soil andtransport them to the berries (Goode, 2003), the soil properties influence the berry’scompositionthroughthechemicalcomposition,thepH,thetexture,thestructure,thedepth,andthecolourandthetemperatureofthesoil(Carey,2001).

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2.3.1 Physicalpropertiesandsoilporosity

2.3.1.1 SoiltextureandsoilstructureTexture means the concentration of macroscopic particles of variable sizes that define soilgranulometry.Thus, therearesandytexture(bigparticles),slimytexture,and“clayey”texture(smallparticles).Soil structure also corresponds to the arrangement of clay and organic matter (as humusmainly).Soil texture and soil structure define the soil’s porosity. The network composed of calcium,humusandclayparticipatesintheaggregationofsandandsilt.Thegivenporositydependsontwothings:

• Theabundanceofmacropores,allowingtheflowofwaterandair(Lanz,2004)aswellastherootdevelopment(vanLeeuwenetal.,2004;Seguin,1986)

• Themicropores,whichkeepwateravailablefortheplant.SeguinandvanLeeuwendiscussthebenefitsofasoilrichinlimestoneandobservecorrelationsbetween thequalityof thewineand the soil’spermeability.Theauthors give examplesof thefollowingsoils:“alkalineandsandysoilsfromChâteauAusone,theacidicgravesfromDomaineLafite-Rothschild, the neutral graves from Cheval Blanc, and also the limestone rich soils inPetrusandChevalBlanc”.Soilpermeabilityalsodefinestheoxygenationrate,whichisakeyelementtotakeintoaccountsincetheroots,withthesoil’saerobicbacteria,respirate.Rootdevelopmentandtheabsorptionof nutritive elements depend on the quantity of available oxygen,which is related to the soilporosity,whichalsodependsonthesoildepth.Thefollowingchapters(2.3.2.3and3.3.1)willgodeeperinthisnutritionalaspectandthesoil-vineinteractionconcerningtherhizosphere.Finally, the water supply, oxygen supply, and root development depend on the depth of thesubstrate,onthissubjectBodinandMorlat(2003,2006)showthatshallowsoilsimprovegrapequality.Moreover, with poor and shallow soils, Seguin (1969, 1975, 1983, 1986) demonstrates acorrelationbetweendeeprootingandbetterberryquality,especiallyforredwines.Thesepostulatesconfirmtheimpactoflighthydricstress.Therootnetworkdensityinshallowsoils also leads to root developmentwithin an evenmoremineral-rich substrate. Then,whatabout themineral impact?Whatabout theabsorptionof thesemineralsandtheirrelationshipwiththetypicityoftheberriesandthewine?Thefollowingchapters(2.3.2.3and4.3)addresstheseunderlyingquestions.

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2.3.1.2 ColourandsoiltemperatureAsregardsthephysicalpropertiesofthesoil,thesoil’scolourseemstosignificantlyaffectgrapematurity.

Indeed, soil colour is related to the absorption and the reflexion of certain wavelengths thatcontributetothematurationoftheberriesandthetemperaturearoundtherootarea(Barbeauet al, 1998a, b). Thus, limestone-rich soils give berries a skin more rich in polyphenol-concentrate (Stoll et al., 2008),whereasdark soilwill return the thermic energy accumulatedduring the daytime through radiance, and thereby help to extend thematurity period for theberries(Fregoni,1977).

2.3.2 Mineralcompositionofsoil,vinedevelopmentandberriesmaturityEventoday,noresearchhasbeenabletodemonstratetheprocessbywhichmineralsfromthesoilareassociatedwiththecolour,thetaste,orpropertiesofwine(Moran,2001).However,asnutrients,mineralsareinvolvedinnumerousbiologicalreactionsandplayacrucialrole in thephysiological development of theplant. Inplantnutrition, there are twogroupsofnutrientsnecessaryfortheproperfunctioningoftheplant:

• Macro-elements:N,K,Ca,Mg,P,andS• Micro-elements:Cl,Fe,B,Mn,Zn,Cu,Mo,andNi(necessaryinsmallamounts)

Onceagain, in thecaseof thevine, thebestwinesare fromvinesgrown incritical conditions,withmoderatedeficiencyconditions,inordertofavourfruitproduction.

2.3.2.1 Nitrogen,potassiumandcalcium,threemainmacroelementsAccording to Saayman (2002), nitrogen and potassium are the main minerals affecting winequality.Toomuchnitrogencan leadtoberrieswith tannins that taste likeunripe fruit.Ontheotherhand,anitrogenandpotassiumdeficiencycanrestrictfermentation.Indeed, theberryquantity isnegativelycorrelatedwithnitrogensupply (Seguin,1986).A lownitrogeninputdecreasesthevine’svigour,theberrysize,andtheyieldbutincreasesthesugarcontent, anthocyanins and concentration of tannins which is favourable to the berry quality,especiallywhilemakingredwines(Chonéetal.,2001;Hilbertetal.,2003).Potassium,meanwhile, is involved inboth the sugar translocationduring theberry’smaturityandtheincreaseofmalicacid/tartricacidratio(GoldspinketFrayne,2001).Thisratioimprovesthemalo-lacticfermentationandslightlyincreasesthepHandchromophorestabilityinwine.For some scientists, nitrogen and potassium are the only elements that illustrate the linkbetween soil composition, quality andwine typicality (Halliday, 1993). And yet, the supply ofthesemacro-elementslikelydependsonotherminerals,soilcharacteristicsanditsinfluenceonberryandwinecompositionnotwithstanding.Thisisthecaseofcalcium.For Saxton (2002 a, b) calcium absorption allows “amore intense terroir expression”, a termquickisoftenusedintheliteratureyetremainsunclear.Moreover, active calcium carbonate improve soil structure and drainage capacity, whiledecreasing the mineralization rate of the organic matter (limiting the nitrogen supply),improvingrootdevelopment(vanLeeuwen,2010)andcontrolingpotassiumabsorptionthankstotransportercompetition(Whiteetal.,2007).

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ThismineralisalsoinvolvedinthesugarcontentandpHoftheberries(MackenzieandChristy,2005). Thus, calcium is not only involved in soil physical properties but also in soil chemicalfertilityandinthecompositionoffruititself.Finally, fromanutritionalpointofview,thesoil-vineinterfacedoesnotseemtobeonlyaboutmacro-elements.With greater frequency, authors highlight the significance of other elementspresentinverysmallamounts;namely,traceelements.

2.3.2.2 Thesignificanceoftrace-elementsRecently, research has been able to show a relationship betweenmicro-elements, also calledtrace-elementsoroligoelements,andthecompositionofgrapes.Indeed, varying levels of sugar concentration (Baumé index) and berry acidity enhance theavailability of some trace-elements in the soil, namely strontium, barium, lead or silicium(MackenzieandChristy,2005).In addition, some research from Dc. Z. Bouzoubaâ (INRA Agadir, Algérie) and Peter Kunz(NeuchâtelUniversity,Switzerland),showthatsilicium,morepreciselysilica,isinvolvedintheabsorption, regulation, and transport of essentialminerals like calcium, phosphor, potassium,magnesiumandsodium.These minerals may have a role in the growth (in thickness and length) of the root system(Lefebvre,2006).Moregenerally,ifthevineseemstoneedonlyasmallamountofnitrogen(30to40units/yearareenough),potassiumandphosphorus,thelimitingnutrientsarethereforetheoligoelements(Cl,Fe,B,Mn,Zn,Cu,Mo,etNi).Thesetrace-elementsarethusdeterminantinthewine’stypicality(Pr.E.Bourguignon,personalinformation).

2.3.2.3 MineralavailabilityInordertobeavailablefortheplant,thesemineralsthatoriginatefromthecrystallinematrixofthe rock have to be uprooted and solubilized. Then, it is themineral composition of the soilsolution,whichbecomesthenutritivemediumfortheplant.

ThemineralavailabilityinvolvesahighCationicExchangeCapacity(CEC),possibleinachargedenvironment, with an abundance of high-area/volume ratio minerals. These conditions aremainly present at the surface of the ground, in soils rich in humus, and limestone,where thewater is easily available and the soil’s biological activity is optimal (Mackenzie and Christy,2005).However,thepreviousreferencesdemonstratethatthewinesthatexpressterroirtypicalityarefromvinesgrowninpoorandshallowsoils.Whenthesoildepthislow,orwhenthevine’srootsgodeeply,allthewaytothesubsoil,theseconditionsofhighCECarenolongeroptimal.Therootsareincontactwithslightlyerodedrock,inalowaeratedandhydratedenvironment,wherethemineralavailabilityismuchlowerfortheplant(Maltman,2013).

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Sinking into thedepths of the soil and subsoil, there is also an increase in variability of traceelements.Here,incontactwiththeparentrock,dwellsthemineralogicalsignatureoftheterroir.Atthisdepth(until5–6m)therootsystemdensityisessentialbecauseofhardconditionsfornutrients, water and oxygen supplies. But overall, the availability of these oligoelements ispossible only thanks to soil aerobic microorganisms and some fungi that allow chelation ofnutrientsandthesynthesisofligandslikesiderophors.Maintainingsufficientoxygenationatgreatdepths is thereforenecessary for theabsorptionofoligoelements that are in contact with the parent rock, which is the terroir signature (Pr. E.Bourguignon,personalinformation).Concerning the availability of nitrogen, this depends on C/N ratio that corresponds to themineralizationrateoforganicmatter(vanLeeuwenandSeguin,2006).Organic matter is not available for the plant as raw material. It must first be oxidized andmineralizedunderhumustoallownitrogentobeassimilatedasnitrateorammonium.This mineralisation is highly dependent on nitrifier bacterial activity and other soilmicroorganisms living in symbiosis with the plant, such as mycorrhizae (Schreiner, 2005).Upcomingchapterswilldetailthisspecificinteractionlater.Ingeneral,soilisamajorelementintheinductionofphysic-chemicalpropertiesofgrapesandalsoinwinetypicality.Influencingthewatersupplyfortheplant,thephysicalpropertiesofthesoilplayaroleinthesugarcontent,theconcentrationoforganicacids,andantioxidantswithintheberries.Theorgano-mineralcompositionofthesoil,andmorepreciselythemineralcompositionofthesoil solution in nitrogen, potassium, calcium and other elements (especially trace-elements)alsoaffectchemicalchangesintheberries.It isthevariabilityofallofthesefactorsthatwarrantstheuniquenessofthesoil inwhichthevinegrowsandthereforetheuniquenessofthegrapes.Althoughfavourableconditionsfortheterroirexpressionaremainlyinpoor,shallowandstonysoils (van Leeuwen and Seguin, 2006), it is native soil fertility conservation, withoutperturbationfromfertilization,thatguaranteesthefaithfulnessofthegrape’stypicalityrelatedtoterroirresources.Thus, this present chapter has attempted to demonstrate that the interactions between thebiotope and the plant are integral the grape’s composition. The precocity of the cultivar, thevariability of climatic conditions, thewater supply, and the concentrationofdissolvedmacroandmicro-elementsdefinesugarcontent,pigmentconcentration,andlevelsofantioxidantsandorganicacidswithinthegrapes.The soil and the climate are not the only terroir components that affect the plant. Thewholeecosysteminwhichthevinedevelopsalsoinfluencestheplant’sphysiologicalresponses.Thus,thisadditionalfactorcontributestothegrapeandwinetypicality.Inside this ecosystem, the microbiota has a very special place because it is involved infermentationand in the transformationof thegrapemust intowine. It is to this topic thatweturnnext.

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3 EvolutionofthenativemicrobialpopulationsdependingontheterroirIn thischapter,only thenativemicrobialpopulationwillbediscussedbecause theyconstitutethe unique bacterial and fungal resources disrupting the development of the local flora anddenaturingthefaithfulnessexpressionoftheterroir.Thesemicrobialpopulations,ormicrobiotabelongtotwogroups:therhizosphere(closetotheroots) and the phyllosphere (surrounding the rest of the plant) interacting with the plantthroughdifferentways.Thispartisabouttheseinteractionsaswellastheconsequenceonthegrapemust.

3.1 PlacedependantcommunitiesThe microbial biogeography based on the berries reveals a non-random repartition of thepopulationdependingontheregion,theclimateandthevariety(Bokulichetal.,2014).Differentperspectivesarerelevant;letusstartonthespatialscale.Thecommunity’sstructurewidelyvarieswithindifferentproductionregions,mainlyconcerningthe taxonomic diversity of fungi and the microbial genetics, regardless of the variety or thevintage(Bokulichetal.,2014).Amongst this diversity, Bokulich’s studies (2014), which took place in Californian vineyards,showthattheproductionplacecanbedefinedbasedontheabundanceofseveralkeyfungiandbacterialtaxa.Although the climatic conditions, such as rainfall, temperature, and humidity change themicrobialpopulation,thestabilityoffungalcommunitiesratherthanbacterialcommunitiescanmakepossiblevineyard’scharacterisationataplotscale(Bokulichetal.,2014).Atthisscale,themicroclimateswithinthefieldgoverntheabundanceofmicrobialpopulationdependingonthefieldorientation:shadeareasundertheleavesorhumidplacesbetweentheberries(Gilbertetal.,2014).However, these differences regarding the microbial populations do not allow any conclusionconcerningtheorganolepticpropertiesofthegrapemustandwine.Indeed, among the strains studied in this American paper, not all of them are involved inalcoholic fermentationandnotallsurviveto fermentationcondition(lowpH,anaerobia,sugarcontent,alcohol).A study fromNewZealand that focused on the repartition of differentSaccaromycescervisiaewithintheMaoriterritoryhighlightsgeneticvariabilitybasedonthewineregions(Knightetal.,2015).Theseconclusionsattesttotheimportanceofmicrobialpopulationlinkedtotheregionalidentityofwine.

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3.2 ThecultivardependantstrainsAnotherpointofviewfromwhichthediversityofthevine’smicrobiota isanalysedfocusesontheplantscale.Theentireplantiscolonizedbymicroorganisms,whichchangeaccordingtotheplanttissues(Fig.1).

Figure1:SchematicrepresentationofthebacterialandfungalpopulationassociatedtoVitisvinifera(Gilbertetal.,2014)

Theoriginofthiscolonizationcanbetracedtotwofactors:thesoilandthelocalecosystem.The soil microbiota, in symbiosis with the plant, colonize the roots. Regarding the soilcharacteristics and plant needs, thismicrobiota changes and leads to a biological equilibriumbetweentheplantandtherhizosphere(Sabateetal.,2002;Lundbergetal.,2012;Bulgarellietal.,2013;Martinetal.,2013).Secondly,thelocalbiodiversity,throughinsects,otherplants,andanimalscolonizestheaerialpartsofthevine(Leveau,2011).The affinity between phyllospheric populations and the cultivar seems to be significant onlyconcerningsomefungi,butneverforbacteria(Bokulichetal.,2014).Accordingtotheauthors,thisaffinitymayinvolveageneticcomponentbetweentheplantandthemicrobiotasurroundingtheberries’surface.Theplantwouldstimulatethedevelopmentofsome strains at the expense of others according to the plant’s growth, possible stresses ordiseases, and invasions. Thus, this interaction would explain the presence of a “standard”microbialpoolanda“cultivardependant”pool.Thus, the microbial resources do depend on the terroir since it is possible to characterizeproductionregionsorplotsthankstotheabundanceofkeymicroorganisms.Thispool,definedbythesoilandtheclimaticconditions,becomesmoreaccuratewhenwefocusontheplant.Thiscanbeconsideredastheterroireffectregardingmicrobialpopulations.

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Thedensityanddiversityofthepopulationdependalsoonagriculturalpractices.Effectively,inbiodynamicfarmsithasbeennoticedthatthereexistsahighermicrobialdiversity(Setatietal.,2012).

3.3 Microbiota-vineinteractionanditsinfluencesonberrycompositionThemicrobialpopulation’sdynamic (which isalwayschanging),definedby the terroir,affectsvine physiology but also grape must composition at the origin of the first steps of alcoholicfermentation. This section details themore or less direct involvement in the rhizosphere andphyllosphereongrapemustandoenologicalpotential.

3.3.1 TherhizosphereinfluenceForC.Bourguignon(1995),boththewine’squalityandtheexpressionofterroirdependonthemicrobialactivityofthevinyard’ssoil.First of all, the rhizosphere affects nutrient availability controlling mineralization and thehumification. Indeed, section2.3.2.1 dealt with the importance ofmoderate nitrogen supply,only possible thanks to an equilibrium between mineralizing bacteria (that make nitrogenavailabletotheplant)andfungalpopulations(immobilizingnitrogeninthehumuscomplex).Thesoilvitalityalsoallowschelationofoligoelements,necessarytomakethemavailabletotheplant(Dc.E.Bourguignon,personalinformation).Similarly,silicaabsorptionbytheplantispossibleonlywhenthismoleculeisonitsamorphousform (Si(OH)4), which is a conformation available only in particular biologic conditions,involvingtherhizosphere(Lefebvre,2006).Themicrobialcommunitiesfromtherhizosphere,whichisafunctionofthesoilcompositionandclimate,arealsoverycloselycorrelatedtocultivar.As for every plant, the vine needs vary along the development. The plant exchangeswith therhizosphere through root exudates that stimulate target microbial populations according tophysiologicaldemands.Thesoil’smicrobialresponses,changingthroughthemicrobialpopulation’sdiversity,affectstheplantresourcesandinfluencessynthesispathwaysofthevinesuchassomearomaprecursors,polyphenol,orotherorganicmolecules(Dc.E.Bourguignon,personalinformations).Thesecompoundslateraffecttheberries’compositionandthewine’sorganolepticproperties.Amongallthesoilmicrobiotastrainsinrelationwiththevine,someofthemseemtospecifictoVitis vinifera. This is the case for Aureobasidium pullalans andHanseniaspora uvarum, whichusuallyrepresentalowpercentageofthesoilmicrobiota(5%)butareisolatedinabundanceinvineyardsoils(Sabateetal.,2002).Someofthesestrainsareevenfoundonthegrape’sskinandonthewallsoffermentationtanks,likeFilobasidiumcapsuligenum(Sabateetal.,2002).Althoughtheseyeastsarenotabletotransformsugarintoalcohol,theyareknowntosynthetizepigments, antifungal resistant molecules and hydrolytic enzymes (Petruccioli and Federichi,1992).Whenthesemicroorganismsareincontactwiththeharvest,theyarethereforeinvolvedinthereactionsthattakeplaceinthefermenters,butthescientificcommunitydoesnotyetrecognizetheiroenologicalsignificance.

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Indeed,onlyonestrainfromthesoil,widelypresentintheberriesskin(50à65%)accordingtoPretorius(2000),isdirectlyinvolvedinfermentationmechanismsthatimpactthetasteandtheflavourofthewine.ThisstrainiscalledH.uvarum(Mateoetal.,1991).Thus,therhizospheremostlyindirectlyinfluencesthemustcompositionthataffectsthenutrientavailabilityfortheplant.However, somestrains fromtherhizosphereseemtobeable toplayamoredirect role in thesynthesisofmoleculesthathaveorganolepticproprertiesorabletogrowinfermenters.Thisisanabilitymostlyfoundwithinphyllospherepopulations.

3.3.2 PhyllosphereinfluenceThe phyllosphere is the microbial flora present on the aerial portion of the plant. They aremicroorganismslikelyexistingonthegrapeberries’dandruff.Onceincontactwithgrapepulp,yeastsandbacteriaconsumesugar,therebyprimingvinificationreactions.On intact berries, the main microorganisms are basidiomycetes, such as Cryptococcus spp.,Rhodotorulaspp.,Sporobolomycesspp.,Filobasidiumspp.aswellasdimorphicascomycetessuchasAureobasidiumpullans(Prakitchaiwattanaetal.,2004;Barataetal.,2008,2012).Theseyeastsarenotable toconsumesugarandtransformit intoalcohol,noraretheyabletosurvive in alcoholic fermentation conditions. However, they synthetize pigments that mayinfluencethewinecoloursattheearlystageofvinification(Setatietal.,2012).Concerningthe fermentativeyeasts, themainstrainsbelongtoascomycetes, likeCandida spp.,Pichiaspp.,etMetschnikowiaspp.,orbelongtofermentativeascomycetessuchasHanseniasporaspp.orKloeckeraspp..TheSaccharomycescerevisiaetypeofyeastsareonlypresentinnegligibleproportions(Setatietal.,2012).Thiscomplexequilibriumbetweenthedifferentspecieschangesassoonasthesugarfromthefruit becomes available because of the maturation or because it’s inside the fermenters. Theberry splitting releases sugar and allows for faster development of the yeasts that are bestequippedtotodegradeit.Ethanol production and acidic pH inhibit and eliminate some yeasts at the expense offermentativeyeasts.Inthelaststagesofthefermentation,thestrainsthatarethemoreresistanttotheseconditionstakethelead.ThisisthecasewithSaccaromycescerevisiae,forexample.Thisfloraequilibriumisthusassociatedwiththegrapeberries’dandruffvariesaccordingtothecultivar,thevintage,andthematurationdegreeoftheberries(Sabateetal.,2002).

3.3.3 ConsequencesontheberrycompositionandthefermentationpotentialofthemustIn the transformation of a fermented product such as wine, the microorganisms involved infermentationplayakeyroleinthetypicalityofthewine.

Inadditiontomicrobiota’ssignificantimpactonplanthealthandmineralavailability,microbialpopulations are at the source of sugar transformation into ethanol, pigments and aromaticcompoundsynthesisspecifictometabolicpathways(Lambrechtsetal.,2000).Thenaturalinoculationofthegrapeberry,throughthephyllosphereandsomestrainsfromtherhizosphere,definestheprimingoffermentations(ethanolicandmalolactic).

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This initialdiversity is essentialbecausedifferent speciesofyeasts areeventually responsiblefor particular compounds like organic acids, alcohol, phenols, esters, sulfur compounds, andmonoterpenes(Swiegersetal.,2005;Sumbyetal.,2010).It is in the early stages of vinification (maceration and initial fermentation) that microbialdiversityisexpressedbeforebeinglimitedbyselectivefermentationconditions.Similarlytocultivationtechniques,fermentationsconductedbythewinemakermustbedoneinawaythatminimallydisruptsthenaturalresources.Thiscareallowsthewinemakertoobtainaproductthatisfaithfultoitsoriginalterroir.Evenifthephenomenainvolvedinthespontaneousfermentationofthegrapemustarecomplexbecause they depend on undetermined microbial flora and inhibitions and interactions stillpoorly controlled and understood, it is precisely the composition of this microbial pool thattypifiesthebiologicalsignatureofthewine.Insomecases, it ispossible tobuildabridgebetweenthenatureof thestrainandthephysic-chemical modification of the must. However, it is still impossible to predict organolepticpropertiesofthewineregardingthemicrobialpopulationpresentontheberry’sdandruff.Thus,thissectionconcludestherangeoffactorsinvolvedinthetypicalityofthegrapeberries’physico-chemicalcomposition.Together, the biotope components (geology, soil and climate) define the constraints of theterroirappliedtothebiocenoseinwhichthebiologicalsystem“vine-microbiota”develops.The sum of the interactions between the biological system and its environment, and evenwithin the vine-microbiota system itself, determines a response perceived in the physico-chemicalandbiologicalcompositionofthegrapemust.Itisthegrapemust’scomposition(insugar,tannins,organicacids,pigments,etc.aswellastheinitialmicrobialpoolcomposition)thattheterroir’sfootprintandtypicalityofthegrapemustareconstituted.However, in thewineproductionprocess, theperceptionof this typicalityshines through thetastingofthefinalproduct.This very last chapter discuss the typicality and the correspondence between sensorialperceptionandthebirthplaceofwine.

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4 PerceptionofwinetypicalityTheperceptionofwinetypicalityrelatedtoitsgeographicorigininvolvestheconceptofmarker-receptor.

Amongthedifferentphysic-chemicalcharacteristicsofwine,itisessentialtounderstandwhichonesaresusceptibletorevealitsidentityanditstypicality.In thecaseofwine, thisperceptioncomeswithdegustation,aprocess thatusesoursensesofsmell,tasteandsometimessight.Onceagain,thehumanfactorisparamountinsofarasitgivesasubjectivedimensiontotheassessmentoftypicality.We are presented with what is arguably the most crucial question concerning the notion ofterroir. Indeed, it’s the existence of tangiblemarkers, recognized by the taster and specific toappellations, that gives the only irrefutable argument explaining the link between theproductionplaceandthewine’stypicality.In the following sections, three types ofmarkers are discussed: a pedologicalmarker using astrontium isotope pair, volatile compounds used as olfactory markers, and the notion ofminerality.Thesethreewillbeproposedasprospectivegustatorymarkers.

4.1 87Sr/86Srisotopepair,apedologicalmarkerAccordingtoMarchionni(2013),thestrontiumisotopes(87Sr/86Sr)canbeusedasapedologicalmarkerandthenallowstolinkwinetoitsinitialproductionplace.ThishasbeendemonstratedwithmorethanfortyItalianwines.

Indeed, the isotope’s proportions, specific to the parental geological material, are stored andtransmitted from the plant to the wine. This isotope pair corresponds to the uniquemarkerwarranting the production place of origin (Mercurio et al., 2014), therefore constituting aparticularlyreliabletraceabilityelement.However,thismarkerhasonlylegalinterest:itallowsfarmerstofightagainstforgerybutdoesnotconstituteanorganolepticmarkerthathasanyaffectonthesensesofthetaster.Inthecaseof wine, even the opening of a bottle opening stimulates the sight and hearing. Then, duringdegustation,aromasandtastesbecomethepotentialmarkersofwinetypicality.

4.2 Thevolatilescompounds,olfactorycompoundsNowadays, the analysis of volatile compounds is a matter of great interest in the field ofoenologybecausethemostofthesecompoundsarederivedfromfermentation.Thedistinctionandthedegustationofwinearelinkedtosensorialanalysisbasedonolfactometry(fromhumannose),togetherwiththeobjectiveanalysisofgaschromatography.In thisapproach, theaim is to isolatesomevolatile compoundsand thendevelopanaromaticprofile of the wine specific to each terroir. Thus, these compounds would correspond toolfactorymarkersoftypicalityandcouldbeestimatedasthearomaticterroirsignature.To do so, a consensus within the group of tasters (such as common sensory descriptors orsimilarflavorintensity)isessentialinordertobuildasensorialmapspecifictothewinethatistested.

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InthecaseofChardonnay,somestudiesshowedthat18aromaticcompoundsdefinethespecificolfactory properties of this cépage, regardless of the production place (Bourgogne, Alsace,Languedoc, Provence, Vallée de la Loire, Vallée du Rhône) or the vintage (2003, 2004, 2005)(Jaffré,2009).It is possible to find markers that discriminate cépage properties. But what about markersboundtotheproductionplace?Concerning the latter, Jaffré’s studies (2009)have focusedon theexistenceofasensorialmaprelatedtosomeappellations:“vinsjaunesduJura,vinsrougesduDuchéd’Uzes,vinsrougesducruFleurie”aswellasChampagnefromCramant.Theseworkshighlightthedifficultyofconsensusandshedlightonanincreasingvariabilityfromtheolfactorydescriptorswhen the surfaceareadecreases.Thus,whereas it seemspossible todrawaromaticprofilefrom”vinsjaunesduJura”(1950ha), itbecomesimpossibleforthe“vinsrougesducruFleurie”(870ha).Concerning Champagne from the village of Cramant, the study from Jaffré (2009) does notsucceedinfindinganycommonolfactoryproperties.However,itunderlinesthepreponderanceofvinificationparametersregardingtheexpressionofthearomaticprofile.Indeed,thisstudyfocusesonCramantwinesmadebyG.H.Mumm&Cie(Reims),Perrier-Jouët(Epernay) or other winemakers (Coopérative Union Auboise, Palmer, Cave coopérative deNogentL’Abbesse).For instance, the olfactory analyses of these wines demonstrate the existence of significantdifferencesbetweenwinesmadebyPerrier-Jouët(plantanddriedfruitaromas)andG.H.Mumm&Cie(flowerandcaramelaromas).Thisconclusion, looking toassignameaningful role to thecellar regarding thewine typicalityhastobetakenintoaccountbutisnotthesubjectofthisreviewabouttheterroireffect.Indeed,the vinifaction technics from these two companies are not known and the use of exogenousstrainsorotherprocessescanbiastheoriginalaromaticprofileofthewineinsofarastheyaddexternalcompounds.Nowadays,itisapparentlynotpossibletoestablisholfactoryprofilesbasedonterroir.Some studies have highlighted common aromatic properties concerning the cépage(Chardonnay) or for a specific region (Vin jaune du Jura), but regarding the scale of anappellationoradomain,thevariabilityistoofinetoestablishalinkbetweengeographicoriginandwinescents.Thisconclusionechoestheresultsfromchapter3.,whichdemonstratetheexistenceofamoreimportantvariabilityintra-vineyardsthaninter-vineyards(Gilbertetal.,2014).Intheprocessofadegustation,thelastsensethatcanidentifythewinetypicalityisthetaste.Ifitisnotpossibletoisolateolfactorymarkerspecifictotheterroir, is itpossibletofindgustatorymarkers?

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4.3 Thetasteofterroir:minerality?Theperceived tasteduringdegustation involves the fourprimary flavours: bitterness, acidity,sweetness,andsaltiness.

Among the gustatory descriptors used by amateurs and professionals, Cees Van Casteren,internationalwine journalist,highlighted in2012that the term“minerality”appeared inmorethan10%ofthe258,000articlesheanalysedfromthefamousAmericanreviewWineSpectator,farmorethantheusualdescriptors“woody”,“floral”,or“fruity”.Despite its recurrent use, the term “minerality” remains unclear. For some people, it is aaromatic complex with sensations such as “strained wines, right, net, without makeup." Forothersitevokesaromasof"flint",notesof"metal"or"pencil,inkandoil"(Bal,2013).In this section, the term “minerality” is discussed through an analytical point of view as themineralcompositionofwineanditscontentofinorganiccompounds.Far from being only a new trendy descriptor in the lexical field of oenophiles, the notion ofmineralityrevealsatrueinfatuationwiththeroleofmineralsinwine.Inoppositiontosensorialanalysis,mineralityisthebasementofthegeo-sensorialdegustationfocusedonthebirthplaceofwine, “mouthfeel”,andthearomasappreciated inretro-olfaction.For the followers of geo-sensorial degustation, minerality constitutes the “signature of thewine’softerroir”(Rigaux,2012).However,thesensationofmineralityremainsimpalpableandabstractandthelinkbetweenthisdescriptor and the place of production remains an intuition lacking scientific proof.Nevertheless, this interest in wine’s inorganic composition primes new research inquiries tofocusontheimpactofmineralsandtheirinteractionswithorganiccompounds.In this context, research has been performed concerning wine’s mineral content and theinteractionbetweenmineralsandwinetaste.SomecorrelationhasbeenobservedbetweenthewinequalityofsomeCôte-du-Rhône(2003and2007)and themineralconcentration,openingthedoortonewhypothesesabouttheoriginoftaste(Vignonetal.,2012).Assimilating the wine’s minerality with its mineral content, Vignon (2012) shows thatsometimesthereisasensorialimpactofthemineralontheprimarygustatorycomponentssuchassweetness,saltiness,acidity,andbitterness(Fig.2andFig.3).Thus,mineralcontentimpactsgustatorybalanceandtheintensityofwine’staste.Forexample,aconsumer can perceive infinitesimal variations in the level of salt, lower than analyticaluncertainty(between0.5and1.5g/hL).

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Figure2:Impactofcationsonwinetastethroughtheadditionofsomemineralsalts(Vignonetal.,2012)The pentagon (or hexagon) area allows the assessment of gustatory intensity fromdifferent samples. Thescoreofeachdescriptormovesthepentagon(orthehexagon)accordingtothecentralstandard(inpurple)andmodifies thebalanceof the taste.For instance,addingsodiummoves thebalanceof the taste towards“long finish” (longueur en bouche), the salinity (salinité) and the sweetness (sucrosité) at the expense ofbitterness (amertume) and acidity (acidité) regarding the white wines from Côtes du Rhônes and at theexpense of bitterness (amertume), acidity (acidité) andastringency (astringence) regarding the redwinesfromCôtesduRhône.

Figure3:Impactsofcationsonwinetastethroughtheadditionofsomemineralsalts(Vignonetal.,2012)Asabove, this figure illustrates theconsequencesofaddinganionson the intensityand thebalanceon thetasteofbothwhiteandredwinesfromCôtesduRhône.Inthiscase,addinganionsseemstoefficientlymodifythescoresofallthedescriptors.Forinstance,addingphosphatemainlyleadstoacidicandbitterwhitewinesandacidic,bitter,andastringentredwines.Forsomepeople, thesestudiesgivea lotofhoperegarding theunderstandingof theoriginoforganoleptic typicality inwine.This is certainly the casewithoenologistDavidLefèbvre,whoaffirmsthat,“mineralsandoligoelmentshaveabiginfluenceonthetasteofwine,evenatverylowconcentrations”.Indeed, themineral content in grape juice is about4g/L for anorganicmatter around300 to400g/L. After fermentation, the mineral content remains almost constant whereas theconcentrationinorganicmatterfallreaching20to30g/L.

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Catabolizing the carbohydrates and organic matter, fermentation ends up making relativemineralconcentrationmoreimportant:therebycreatingamineralization(D.Lefèbvre,personalinformation).Additional experiments that add to thoseofVignonet al. (2012) showa relationbetween theperception of saltiness and the casein content in milk. The molecular weight and theconcentration of proteins interact with sodium ions and modifies the salinity felt by theconsumer(D.Lefèbvre,personalinformation).Because fermentation leads to molecules with a lower molecular weight, it is thereforeconceivable to think that the taste perception of the wine depends largely on the mineralsplayingtheroleofflavorenhancer.Ifalinkbetweenthemineralcompositionofwineandtasteexists,thisdoesnotgiveanyproofconcerningtheexistenceofalinkbetweenterroirandtaste.As recalled by the geologist Maltman (2013), there cannot be any direct links betweenwineminerality and mineral composition of the geological material, given the erosion process,solubilisation,chelationandrootabsorptioncontrolledbyactiveexchanges.Gilles Flutet, specialist at INAO, shares the samepoint of view. In his view, soil can affect themineral compositionof thevinebutnotnecessarily themineral compositionof thewine (Bal,2013).In order to highlight sensorial existence specific to the notion of terroir,we should thereforeconduct research analyzing both themineral profile ofwines and the perception of taste andscents,betweendifferentappellations.Unfortunatelythiskindofstudyislimitedbytwomainconstraints:

1. Atechnicalconstraint,boundtothesubjectiveperceptionoftaste.AccordingtoPatrickMacLeod, “taste is the result of a confrontationbetweenour receptors andourbrain.Because of large genetic differences between individuals, there exist as manyperceptionsasthereexisttasters(…)Wehave347genescodingforolfactionreceptorsagainst4forthecolorandseveralhundredsregardingtaste!(…)Therefore,thetasteofwine depends asmuch the taster as thewine itself! (…) The universal taste does notexist!”(Raisin,2015).

2. A political and economic constraint related to the act of challenging the notoriety ofappellationsthataccepttoparticipateinthesestudies.Indeed,EuropeanandespeciallyFrenchwineregionshaveculturallyverycloserelationswithterroir.Thewholenationalvineyardorganisationisbasedonappellationsthataresupposed to be distinctive terroirs. In France, it is the terroir that is thought to beresponsibleof the typicalityofwines.Thus, youcan imaginewhatwouldhappen ifnoscientificproofsarefoundbetweentheorganoleptictypicalityofafamouswineanditsactualplaceofproduction…

Despiteitsrecurrentuse,thenotionofmineralityremainsunclearandtheimpactofmineralsonwinetypicalityispoorlystudied.Theconcentrationof inorganiccompoundsseemstoplayasignificantroleinthetasteofwinebutnothing,atleastnothingsofar,bindsthesepropertiestothegeographicoriginofterroir.

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It is only convictions and intuitions that grantminerality an oranoleptic signature expressingterroir.L.Bourguignon,fromtheLaboratoiredeMicrobiologiedesSols(LAMS)arguesthat,

to force the root to delve deeply into the soil to establish proximal relationshipwith theparentrock,tofavourlivingsoilthatmakesthemineralsavailablefortheplantarethetwopracticestogetabettermineralityinwine.Andyet,nobodyknowsexactlyhow.

Finally, note that the increase in the occurrence of the term "mineral" in the language ofoenologistsalsocorrespondswithachangeinmarkettrends.At a timewhen techniques producewines that are prone to be richer in alcohol and aromas,thesewinesarenowconsideredas“toomuch”;toorich,toofragrant,toowoody,andtoowarm.Or,inanutshell:toomade-up.Hence a claim in favour of simple wine: limpid, crystalline, austere, and almost acetic. Themineral characterwould evoke a return to authenticity and simplicity. Actually,minerality is“what remains, what will persist, what suggests a sustainable base” says Michaël Moisseeff,aromaticienanddoctorinplantbiotechnology(Bal,2013).Wecanalsosurmisethatinterventionistpracticeswillmostlikelyprocuremoremineralwines.Minerals, as stable elements, are more prone to remain intact, from the soil to the vine andhypotheticallyfromthevinetothewine.Gatheringtheconclusionsofthelastchaptersofthisreview,wecometothefollowingcorollary:lessinterventionistpracticesgenerateamorefaithfulexpressionofterroir.Withoutleavingthefieldofhypotheses,wecanimaginethattheexpressionoftheterroircouldendupinamineralprofileofthewine,thelatterplayingaroleintheperceptionofthetasteofwine.However,itisclearthatbeforewecanaffirmorrefutesuchaproposal,furtherresearchisneededinthisfield.Therefore, the perception of typicality is still in question. If an isotopic marker has beenidentifiedtowarranttraceabilityinwine,nomarkerregardingorganolepticpropertieshasyetbeenidentified.The sensory existence of terroir remains unresolved and in need of more research, in botholfactoryandtasteperspectives,bothofwhichmustbeelucidated.In this context, hope is given by the study of inorganic chemistry and interactions betweenmineralsandthesensoryperceptionofwine.Ifalinkbetweenterroirandwinetypicalityhasnotbeenhighlightedsofar,thisquestionisnotanenigmaanymoreforsomecheeses;thisisthecaseforComté.In 2000, a team from Franche-Comté University managed to show correlations between theproductionplaceofAOCComtécheesesandtheirsensorialmapandtherebyconcludeaboutthelinkconnectingtheterroireffecttocheesetypicality(Monnetetal.,2000).SimilaritiesandspecificitiesofAOCComtécheesareduetowildmicrobiota.Fromthebeginningofmanufacturingtotheendoftheaging,thedynamicofthesenativemicrobialspecies,relatedtotheenvironment,givesthespecificflavourofthesecheesesandthediversityoforganolepticprofiles(Monteletal.,2014).Taking inspiration from this research, the sequencing and the use of so-called “omics”technologymightbeapromisingwaytoelucidatethequestionoftheterroireffectonwine.

24

Conclusion

Terroir,definingaproductionunit,doesexistandconditionaparticularresponsefromthevine-microbiotabiologicalsystem.Thegeology,climate,andsoilpropertiesareattheoriginofgrapetypicality,whichdependonthecultivaraswellasagriculturalandoenologicalpractices.Ifthescientificcommunityhashighlightedaphysico-chemicalandbiologicalsignatureofgrapesrelatedtoterroir,thequestionofthesensoryexistenceoftheterroirisstillunproven.However, the mineral content of wines, associated with their production place is still anuntappedandpromisingperspective.Additionalresearchmustbeperformedinthis fieldwiththecollaborationofvineyardsandappellationthatarewillingtoaccepttheinevitablechallengethisresearchposestotheircredibility.ThisisthechallengetoFrenchvineyards:accepttoundergothistypeofstudywiththepotentialrisk of your image being damaged but with the exciting opportunity to prove the inimitabletypicalityofyourwine. Either this, orwewill continue to remain in theunsteady realmof thehypothetical and continue to be exposed to increasing competitions with new productioncountries.

25

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