pH对红茶冷后浑粒子形成和固形物提取率的影响

pH对红茶冷后浑粒子形成和固形物提取率的影响 pH对红茶冷后浑粒子形成和固形物提取率 的影响 ji 浙江农业大学21(5):525--532.1995 JourofZhejmngAgr~uLturaLUniversity EffectofpHonCreamParticleFormationandSolids ExtractionYieldofBlackTea LiangYuerong;R.dBee(1TeaResearchInstitute.ZhejiangAgriculturalUniversi- ty,Hangzhou310029,China;2UnileverResearch,UK) AbstractEffectofpHonteasolidsextractionyieldwassignificantinincreasinginstanttea yield.Solidsextraction3deldwasdoubledwhenteawasextractedatpH1.2comparedtothatex— tractedinboilingdistilledwaterwlrhnormalwaterpH.Hencouragedblackteacreamparticle formationbyeitherreleasingmoresolidsintotheinfusionorstimulatingpolyphenolstoreactwith polysaccharidesandnucleophilicgroupsonproteininteainfusions.HPLCre sultsrevealedthat theaflavinsandteacatechinswereleadingsubstancesaffectingthe[ormationofcreamparticlesand infusioncolour.TheaflavinsandsometeacatechinssuchasEGCG,ECGandEGCweredissociat— edordegradedunderalkalineconditionandthusteacreamparticlestendedtodissolveandteainfu sionbeccamedarkinediour.Stepwiseextractionofinstantteasusedforicedteaandnoi-rnaIdrink— ingbycontrollingtemperatureandpHwasalsodiscussed. KeywordsBlacktea;pHIcrP21mparticle;solidsextractionyield;instanttea;HPLC theaflavins;catechins 梁月荣,罗德尼?毕;(1浙江农业大学茶叶研究所,杭州3100292英国 联合利华研究所) pH对红茶冷后浑粒子形成和同形鞠提取宰的影响.浙江农业大 学,1995,21(5):525—532 a摘要pH对茶叶固形物提取率的影响在提高速溶茶产量中有重要 意义.在pH1.2时提取,茶 叶固形物产量比用正常pH的沸蒸馏水提取时高1倍.H通过提高茶 场的固形物浓度,促进茶多 酚与茶汤中的多糖或蛋白质分子的亲核基反应而增加红茶冷后浑 粒子的形成.HPLc结果揭示.茶 黄素类和茶叶儿茶素类是影喃红茶冷后浑粒子形成和场色的重要物质.在碱性条件下,茶黄素类和 某些儿茶素类,如EGCG,ECG和GC产生离解或降解.以致冷后浑粒子趋于溶解,茶场色泽变黑, 文中对控制温度和pH生产冰茶用速溶茶和普通速溶茶的分步提取法也提出了讨论. 关键词 中圉分类 茎;,p—H;毪重堡墼王;!些产量:速溶茶;HPLc;童重量;苤童耋 $571.1:T$272.5——工— 弋s.,.专 MainPolyphenolicoxidationproducts inblackteainfusionarethearubigins(TRs) andtheaflavins(TFs)whichamountto 3O一6Oofinfusionsolidsandpredomi— nantchemicalcompositionsofteacream Received1995—04—11 荐{ whichisacolouredprecipitateinsuspesion formedasastrongblackteacoolsdown. TFscontentwaspositivelycorrelatedwith teaqualityormarketteaprice2_.The creamingabilityofblackteawasalsoanin— dicatorofblackteaquality.However, creamingisalsoamajorprobleminproduc— 526浙江农业大学21卷 tionofcoldwatersolubleitedteabecauseit makestheicedteabecomeaturbidliquor whichisnotfayouredbyconsumers.TFs andTRshaveacidicproperties[.Acidifica— tionofteainfusionbysulphuricacidresuh— edinpartialprecipitationofthecoloured oxidationproductsandwasthereforea meamsforencouragingaconsiderablede— greeofseparationoftheoxidationproducts fromunchangedflavanolsinblacktea[‘]and obtainingacoldwatersolubleinstanttea foritedteaproduction.Teacontainedabout 45%ofextractablesolids,buttheyieldof instantteawasonly300gperkgteainpro— ductinn[.Hlevelaffectedtheeauilibrium concentrationofTFsandmoreTFswere liberatedwhenteawasextractedatlower pH[.AspHofaninfusionwaaraised,the infusionbecamedarkandlostconsiderably itscreamingability[.Thusbehavioroftea extractedatextremePHsmightbeofgreat interesttobothcontrollingthecreaming downofcoldwatersolubleinstantteaand raisingyieldofnormaldrinkinginstanttea. Thepresentworkissettoinvestigatethe effectofextractionpHonteacreamparticle formationandpolyphenoliccompositionof teainfusionandsolidsextractionyieldof blacktea. 1Materialsandmethods 1.1Determinationofcreamparticlesize? volumeconcentrationandobscurationoftea infusions 60gl~Gtip(acomercialblackteapro- ducedbyUnileverPLC.UK)wasbrewed with2000mLboilingdistilledwaterfor10 min.Thehotinfusionwasfilteredthrough aplugofCottonwoo1.Whentheinfusion cooleddown,itwastransferredinto8phs. ticcontainers,eachofwhichcontained45 mL_Infusionsinsevenofthecontainers wereadjustedtopH1.2.2,3,7,9,11and13 with3mol/LHClor3mol/LNaOH (FisonsPLC)respectivelyandtheotherone remainedatitsnaturaIpH4.9.pHwasde— terminedbyM84pHmetre?duringwhich theinfusionwasswirledwithamagnetic fleaonamagneticstirrer.Alloftheinfu— sionswerefinallydilutedto50mLand stoodovernight.Creamparticlesize,vol- umeconcentration(vo1.conc.),specificsur- facearea(sp.s.a.)andliquorobscuration weredeterminedbyaS——2MalvernMaster. sizerandthebackgroundvffaameasured withdistilledwater.Valuesofvo1.conc., sp.s.aandobscurationweredirectlyread fromtheMalvermMasterslzer. TounderstandtheeffectofpHofWa— terusedtObrewtea0ncreamingdown, cupsofdistilledwaterwereadjustedtopH 1.1,1.2,2,3,4,5,6,7,9?11accordingto abovemethodandthenheatedtoboilingin amicrowaveovenforbrewingtearespec— tively.3gPGtipwasbrewedwith100mL oftheboilingwaterfor10minandtheinfu— sionswerealsofilteredasabove.PHofthe infusionswasmeasuredbyM84pHmetre. 45mLoftheinfusionswastransferredtoa glassbeakerandadjustedwith3mol/LHC1 or3mol/LtopH4.9,anormalpHofblack teainfusion.andthenwasdilutedto50mL andstoodovernight.Creamparticlesize, vo1.conc.andsp.s.a.ofthedilutedinfu. sionswezedeterminedasabovemethod. - 7 5期粱月荣罗德尼?毕pH对红茶降后挥粒子形成和固形物提取率的 影响(英文)527 1.2Determinationofteasolidsextraction yields 3gPGtipwasextractedwith100mL boilingdistilledwateratpH1.1,1.2,2,3, 4,5,6,7,9,1lforl0rainandthehotinfu— sionswerefilteredthroughaplug6fcotton woo1.Volumeofeachoftheresultantinfu— sionswasdeterminedwhentheycooled downtoroomtemperature.Infusionsolids concentrationwasdeterminedbydrying5 mLofeachinfusionat80?for48hr. Solidsextractionyield(SEY)wascalculat— edfromfollowingequation: sEY(g/kg)=Solidsconcentrat D io r n y (g te / a m w L e ) igh X t(k Infg)usi—onv—olume(mL) 1.3HPLCanalysis 1000gfreshleafwhichwaspicked fromgreenhouseatUniliverResearch,UK waswitheredatroomtemperaturefor14hr andthewitheredIeafwasmincedbyalabo— ratorymincer.Themincedleafwasplaced inastainlesssteeltraytofermentfor3hr at26C.40gfermentedleafwastransferred toa500mLglassbeakerandheatedto90C byamicrowaveovenfor3raintostopits ferrnentation.Thelearwasthenbrewed with300mLboilingdistilledwaterforl0 min.Thehotinfusionwasfilteredthrough WhatmanNo.541Paper.2quotasofthe filtrate(45mLeach)weretranferredto2 glassbeakersrespectively.Oneofthemwas adjustedtopH9.45with3mol/LNaOH andtheotherremaineditsnaturalpHleve1. Thetwosolutionswerethendilutedto50 mLbeforeinjectedintoHPLC,respective— ly.HPLCwascarriedOutaccordingtothe methoddescribedbyBaileyetal[. Thenumberofreplicatesinalltestsof thispaperwas2andthemeanofthetwo replicateswaspresented. 2Results 2.1EffectofpHo[iteacreamparticle formationandliquorobscurati[1n Fig.1showedthatcreamparticlevol umeconcentration(vo1.conc.)inteainfu— sionswasdecreasedwithincreaseofinfu— sionpHfrompH1.2topH9andthenwent upslightlyfrompH9topH13.Asharpin- creaseinvo1.conc.wasseenaspHde— creasedfrom3to2,thelatterwas 0.4416(v/v),almostdoublethatofthe former.Vol.cone.wasthe】owestatpH9, andonly9.9ofthatatpH1.2.Infusion obscurationshowedthesametendencyas vo1.concdid.Maximumvalueappearedat pH1.2andlowestatpH9andremainedat 65一68atpH4—7.Creamparticlesize wasalsoinfluencedbypH.Fig.1showed thatmaximumvalueinthecurveofsp.s.a. withfunctionofinfusionpHappearedat naturalinfusionpHandsp.s.a.wentdown asinfusionpHappearedatnaturalinfusion pHandsp.s.a.wentdownasinfusionpH wasadjustedtoavalueoflowerorhigher thanitsnaturaIpH.Fromcreamparticle sizedistributionofinfusionswithvarious pHs,twotypesofdistributionwererecog- nized.FrompH3topH7,particlesizedis— tributiondiagramsshowedsinglepeakand over70(v/v)ofparticleswasinsizeof diameterfrom0.2btmto0.6btm.Particles below1mindiameteramountedto90of 浙江农业大学2l卷 tota1particlevolumeininfusion.Whenin— fusionpHwaslowerthanpH3orhigher thanpH7,particlesizedistributioncould bedividedintotwofractionsot2theparticle sizescale.Firstfractionwasincolloidal particlesize[]anditsaveragesizewas around0.35umwhichwasthesameasthat ininfusionwithnorma1pH.Secondfraction ofparticleswasinawiderangeofsizerang— ingfrom3mto70mwhichwasabove coloida1particlesize.Particlevolumeratio offirsttosecondfractionvariedwithpH, forexample8;2atpH1.2andabout1:1 stpH9.Theseresultsalsosuggestedthat thedecreaseofaveragesp.S.a.andincrease ofaverageparticlesizeininfusionswithex— tremepHlevelwereattributedtohighratio ofthebignon—colloidaltocolloidalparti— cles.Fig.2showedtheteacreamparticle sizedistributionofinfusionsatpH1.2,pH 3andpH9.4.Whenteawasbrewedin埘a terswithpH4—7,infusionspHremainedat a1eveIofnorTNaIteainfusionpH(table1) andcolouroftheseinfusionsIookedalsothe sameasthatOfnormalblackteaIiquor. However,ifteawasextractedatpH2or below,theobtainedinfusionshadapHval— ueclosetopHofwaterwhichwasusedtO brewteaandlookedpalelycloudyincolour eveniftheywerehot,forexample70C. WhenalIinfusionsextractedatvariouspHs wereadjustedtopH4.9,theyweredeeply redincolourexceptforthoseextractedat pHoflowerthan2whichwereslightly greyish.InfusionextractedatpH9gavethe lowestliquorobscurationandparticlevo1. c.nc.Thehighestvo1.Conc.andobscura— tionappearedininfusionextractedatpH1. 1(fig.1).Nodistinctdifferencesofparticle sizedistributioncouldberecognizedbe— tweeninfusionsextractedstvariouspHS whentheinfusionswereadjustedtOpH4.9 afterextraction.Therefore,changesofthe obscurationininfusionsextractedatvaroius pHswereinducedmainlybyvariationof vo1.cone.becausetheobscurationshowed thesametendencyasvo1.cone.(fig.1,2) InfusionpH Fig.1EffectofiafilsionpHonformation ‘ Enft姻cr姻m u 目 《 们 吼仉仉 吉_吐 L吼吼 .譬芒,嚣0 5期粱月荣罗德尼?毕pH对红茶冷后浑粒子形成和固形物提取率的影响(英文)529 9? 8? 7? 一 喜6? ,一5? 譬 84. > 3? 2? 1. PaMiclesi2e(m) 2.2EffectofpHonteasolidsextraction yield Variationofteasolidsextractionyield withpHwassimilartothoseofteacream particlevo1.cone.andliquorobscuration withpH(fig.1&3).Moreteasolidswere extractedwhenteawasextractedatex— tremepHconditions,especiallyunder stronglyacidiccondition.Totalsolidsex— tractedatpH3topH11variedfrom270— 290g/kgtea,butthefiguresweredoubled atpH1.1(fig.3). 2.3EffectofpHoncompositionof I~lyphenolsinblackteainfusion Over50peakswereresolvedinHPLC chromatogramofPGtipinfusionat280 rim.Peaksa,b,c,fandiweremajorcon— tributorsto280nmabsorbanceaccordingto thepeakarea,especiallypeakf,over40 Fig.2Particlesizedistribution atvariouspH WiterpH Fig.3EffectofpHonsolidsextractionyield oftotal280nmabsorbance.PeaksC,d,e. f,iandjwereidentifiedbobegallicacid, (一)~pigallocatechin(EGC),(一)一epicate— chin(EC),caffeine,(一)一epigallocatechin— gallate(EGCG),(一)一epicatechin—gallate (ECG)accordingtoauthenticsubstances. respectively.Peaksk,1.mandnwereTF. TF3G,TF3GandTF3,3DGrespectivelv accordingtopreviousreferencesE.’l1_. 53O浙江农业大学21卷 Itwasshowedfromtable2thatchemi— calcompositionofblackteainfusion changedgreatlyasinfusionpHwasraised topH9.45frompH4.9,itsnaturalpH. Firstly,TFs,especiallyTFandTF3Gwere seriouslydestroyed.TFwhichcontributed 30.7oftota1TFsabsorbanceat280nm ininfusionpHof4.9couldnotbedetected anymoreat280nmatpH9.45.Ontheba— sisof280nmabsorbance,88ofTFswas lostatpH9.45(table2).Secondly, EGCG,ECGandEGCreducedt03%,55% and97oforiginalcontentrespectively, butmorecaffeine,gallicacidandECwere detected.Theincreaseofcontentsingallic acidandECmaybetheresuhsofdegrada— tionordissociationofECGandEGCG. Whymorecaffeinecouldbedetectedat higherpHlevelremainstobeinvestigated. Thirdly,someunidentifiedsubstances, suchaspeaksa,b,gandhwerealsode- creasedgreatly. 3Discusion Foursituationsmightbesupposed abouttheeffectsofpHonteainfusion creamparticleformation.Firstly,some polyphenolgalloylesters?suchas(一)一epi— catechin—gallate(ECG),(一)一epigallocate— chin—gallate(EGCG),theaflavin一3一gallate (TF3G),theaflavin一3-gallate(TF3G) and.theaflavin一3.3’-digallate(TF3,3DG) degradedunderstrongacidicconditionand formedsometransientintermediatespecies whichmightbecapturedbypo1ysaccharides andnuleophilicspeciessuchasHS-andHN— onprotein,whichinturnresultedintea creamformationorliquorhaze.Secondly, asteawasextractedunderextremelyacidic condition.Hliberatedsomeextrasub— stanceswhichcouldnotbeextractedunder normalbrewingpHcondition(fig.3). Theseextrasubstancesweretheaflavins[] andmightalsoincludedp01ysaccharidesand proteinetc.Inthiscase,creamparticlefor— mationwasencouragedbyincreaseofinfu— sionsolidsconcentrationthoughtheinfu— sionswereresumedtotheirnorma1infusion pHafterbrewing.Thirdly,underalkaline condition,contentofsometeapolyphenols suchasTF,TF3G,TF3G,TF3,3DG, EGCG.ECG,EGCdecreaesedbecauseof degradationordissociation(Table2).They wereagroupofmajorteacreamcompo— nentsandtheirdecreaseresultedinless creampartcleformation.Fourthly,partial increaseofvol:conc.atpH11orabove wasassumedtobeinducedbyalkalineaLl— tooxidationofteaflavanolswhichhadnot beenoxidisedduringteafermentationpro- tessbecauseunderalkalinecondition, polyphenolswerereadilytransformedinto quinoneswhichmaythenreactedwithnu— cleophilicgroups,suchasNH2一andSH—on proteinsunderalkalineconditionsc?13]. Degrati0nanddissociationofTFsare themajorfactoraffectingchangesofinfu— sioncolouratvaiouspHlevels.Itwasob— servedthatasinfusionwasraisedt0pH9or above,theinfusionbecamedarkandcol— loidalparticlesofteacreamwerepartially disolved(fig.1).Thesephenomenawere closelyconnectedwiththe1OSSoftea polyphenolics,suchasteaflavanolsand TFswhichwerebelievedtobegroupsof 5期粱月荣罗德尼?毕pH对红茶冷后浑粒子形成和固形物提取率的 影响(英文)531 Table2HPLCresultsofinfusionswithdifferentpHsat280? majorcomponentsinblackteaeream.TFs mighthedissociatedanddegradedunder alkalinecondition.ThedissociationofTFs canresultinformationofanionorsalt formsofTFswhichlosttheiroriginalor— angeyellowisheolour.SomeofTFsmaybe degradedintoTRsandthelatter,Which havefairlystrongacidproperties,were thenpresentasanionorsaltswhichwere moredeeplyeoloruedthanitsoriginalforms 0fTF.Thedissociationwasassumedtohe reversiblebutthedegradationirreversible. ThatiswhytheinfusioncolourwithpH9 orabovewaspartiallyressumedwheninfu— sionpHregaineditsoriginalPH4.9. Histheineentiveoftheincreaseof teasolidsextractionyield.Understrongly acidiccondition,theeffectofpHontea solidsextractionyieldmaybeattributedto actionofHontealeaf,alteringlearstruc— tureinsuchawaythatsomeextrasolids wereliberated.Hmightopenuppartsof learstructurewhichwereusuallyinaccessi— bleandhadmorewatersolublecomponents suchasTFsandTRshereleasedfromlear. EffectofHonequilibriumconcentrationof TFswasconfirmed;.Ontheotherhand, someinsolublesubstancessuchaspolysac— charides,pectinandproteinetcmaybehy— drolysedduringbrewingunderstrongly acidiccondition.Maximumsolidsextracted fromteawithhotwaterwasabout450g/kg tea,whileabout600gsolidsperkgtea couldheobtainedwhenteawasextractedat pH1.1(fig.3).Thissuggestedthatcn.15O gmoresolidsperkgteawasreleasedbyae— tionofH.About1moresolidswasab— tainedwhenteawasextractedundercondi— tionofpH9orabove.TFsweredissociated underalkalineconditionc.Itmaybeas— crihedtothatTFsandTRsweredissociated insuchawaythattheybecamemorefree andeasilyextractedOut.Inthiscase,noin— solublecomponentswerehydrolysedand liberatedand?