Extraction-of-the-essential-oil-of-thyme-and-black

ExtractionoftheessentialoilofthymeandblackpepperbysuperheatedsteamMouinRouatbia,b,*,AlbertDuquenoyb,PierreGiampaolicaDOMENA—Avenuedu8e`meRe´gimentdesHussards68130Altkirch,FrancebENSIA—De´partementGIA—UMRGe´nial—1,AvenuedesOlympiades91744MassyCedex,FrancecENSIA—De´partementCSNAAC—1,AvenuedesOlympiades91744MassyCedex,FranceReceived18April2005;accepted9November2005Availableonline27December2005AbstractSuperheatedheatedsteamwasusedtoextractvolatilesfromthymeleavesandblackpepperfruits.SteamandextractedvolatilesarecollectedinacondenserandessentialoilsareseparatedfromthecollectedmixturebysolventsandanalysedbyGC.Resultsshowthattheyieldofextractionhasanasymptoticalevolutionwithtimeandincreasewithsteamtemperatureandflowanditishigherforgroundblackpepperfruits.However,thequalityoftheextractislowerwhenthesteamtemperatureishigherthan175C.2005ElsevierLtd.Allrightsreserved.Keywords:Superheatedsteamdistillation;Thyme;Blackpepper;Quality1.IntroductionEssentialoilshavebeendefinedastheproductsobtainedfromrawmaterialbywaterorsteamdistillationor,inthecaseofCitrusfruitsbymechanicalprocesses(AFNOR,1988).Inpractice,fourmethodscanbeused:steamdistil-lationappliedonfreshordriedmaterial,hydrodistillationwithadditionofwatertotheplantmaterial,squeezingtheCitruspericarpandpyrogenationofthecrustorthewoodofsomeplantmaterials(Garnero,1996).Wenoticeherethatsteamsweepingandhydrodistillationextractonlyvol-atilesandnottheheavyaromaticconstituents.Superheatedsteamisasteamwhichtemperatureishigherthansaturationtemperatureattheconsideredpres-sure.Itisusedindrying(Barbieri,Elustondo,&Urbicain,2004)andbaking(Burg,Fraile,Bouallou,&Renon,1993)butitislittleknowninthedomainofessentialoilsproduc-tion.Infact,thefewworksinthisdomainmentionthattemperatureshigherthan230Ccausecharringandpartialpyrolysisofthebiomassandthedecompositionoftheessentialoilandthattheidealoperatingtemperatureisbetween205and220Cforflashessentialoildistillation(Boucard&Serth,1998).Otherauthorspointoutthattheproductionoffumesaromafromwoodusingsuper-heatedsteamgeneratespolycyclichydrocarbonsthatarecarcinogenic(Peyron,1992).ThymeandblackpepperarerespectivelyaromaticplantandspicethatoriginaterespectivelyintheMediterraneanregionandinIndia.Theyarewellknownfortheirantisep-tic,carminative,antimicrobialandantioxidantproperties(Lee,Umano,Shibamoto,&Lee,2004;Pino,Rodriguez-Feo,Borges,&Rosado,1990).Thymeandblackpepperhaveseveralchemotypes,sotheyieldandthecompositionoftheiressentialoilsarevariable.Theaimofthisworkwastostudytheeffectofsteamtemperatureandflowontheyieldandthequalityofessen-tialoil.Inthecaseofblackpepper,theeffectofgrindingwasalsostudied.0260-8774/$-seefrontmatter2005ElsevierLtd.Allrightsreserved.doi:10.1016/j.jfoodeng.2005.11.010*Correspondingauthor.Address:ENSIA—De´partementGIA—UMRGe´nial—1,AvenuedesOlympiades91744MassyCedex,France.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](M.Rouatbi).(2007)708–7142.Materialandmethods2.1.MethodsGaschromatography-perichromunitwasusedtochar-acterisetheessentialoilquality.0.1gofessentialoilwasdissolvedin5mloftetradecaneinethersolution0.05M,usedasaninternalstandard,and0.1llofthisdilutedoilwasusedforanalysisunderthefollowingGCconditions:Supelcowax10stationaryphase(30m·0.32mmi.d.,filmthickness1lm;oven:40Cfor2min,then4C/min(or5C/minforblackpepper)upto200C,finally5minat200C;detector:FID,detectortemperature:250C,split-lessinjectiontemperature:250C,carriergas:hydrogen.Thecolourofmixturescollectedintheexitofthecon-denser(volatilesandwater)wasmeasuredwithaMinoltaCR-300colorimeterandtheabsorbanceofblackpepperoleoresinwasmeasuredinaJascoUV–Visspectrometer.ThymolandpiperinewerepurchasedfromFluka,limonene,b-caryophyllene,diethyl-ether,sodiumsulphateanhydrousanddichloromethanefromFisherScientific,n-pentanefromAcrosorganicsandtetradecanefromSigmaAldrich.2.2.Thymeandblackpepperessentialoilssweepingbysuperheatedsteam(SHS)Driedthymeleavesandblackpepperfruitswerepur-chasedfromalocalmarket(France).Theexperimentaldistillationdeviceiscomposedofasteamgenerator,asteamheater,achambermadeofastainlesssteelpipe(10cmlength·2cmdiameter)usedtocontainthespiceandacold-watercondenser(Fig.1).Threethermocouplesmeasurethetemperatureofsuper-heatedsteamandoftheatmosphereattheentranceandexitofthechambercontainingthespice.Theexperimentsconsistinfillingacottonsachetwithspice(7gofthymeor10gofblackpepper),toplaceitinthechamberandtosweepitwithsteamattherequiredtemperature.Theblackpepperwasusedinwholefruitsorgroundedinachopper(MOULINEX,Ecully,France)of0.6lcapacityfor1minwithabladespeedof500rpm.Thetripletracksvalvedeviatesthesteamfromthesachetuntilitreachestherequiredtemperature.Thesteamandextractedvolatilesarecollectedinacondenser.SHSflowratesof1.6and2.5kg/hareused.Toobtaintherequiredtemperaturesof100,175and250Cattheentranceofthepipe,steamtemperaturemeasuredatT1were110,185and270C.Theextractionslastfor10,20,30and40min.Essentialoilswereisolatedfromwaterbythreesuccessiveextractionsinaseparationfunnelby,everytime,30mlofmix