FRAP(96). DPPH(04)

FoodChemistry106(2008)5–551

www.elsevier.com/locate/foodchem

JuicecomponentsandantioxidantcapacityofcitrusvarietiescultivatedinChina

GuihuaXua,b,DonghongLiua,JianchuChena,XingqianYea,*,YaqinMaa,JohnShicaDepartmentofFoodScienceandNutrition,ZhejiangUniversity,KaiXuanRoad268#,Hangzhou310029,China

bDepartmentofFoodScience,HenanInstituteofScienceandTechnology,Xinxiang453003,China

cFoodResearchCenter,AgricultureandAgri-FoodCanada,Guelph,Ontario,Canada

Received9April2007;receivedinrevisedform5June2007;accepted5June2007

Abstract

Juicesfromfifteencitrusvarieties(sevenmandarins,foursweetoranges,onelemon,onegrapefruit,andtwopummeloes)ofChinawereinvestigatedmainlyonqualityparameters,totalcarotenoid,phenoliccompounds(totalphenolics,flavanoneglycosides(FGs),andphenolicacids),andantioxidantcapacity(ferricreducingantioxidantpower(FRAP)assayand2,2-diphenyl-1-picrylhydrazyl(DPPH)assay).Amongthefifteenvarieties,Bendizaohadthehighestcontentoftotalcarotenoid(10.02mg/L),Satsumahadthehighestcontentofnarirutin(288.12mg/L),Yinzaochenghadthehighestcontentofhesperidin(533.mg/L),andHuyouhadthehighestcon-tentofnaringin(348.53mg/L),neohesperidin(265.25mg/L)andtotalFGs(746.08mg/L).Asfortotalphenolicacids,Liubenchenghadthehighestcontent(72.61mg/L).Hybrid439achievedthehighestAAcontent(631.25mg/L),andthehighesttotalphenolics(1555.49mg/L)andthegreatestinhibitionofDPPHradical(61.62%).Hamlinhadthehighestascorbicacidequivalentantioxidantcapacity(AEAC:9.31mg/L)determinedbyFRAPassay.CorrelationcoefficientsofAA,totalphenolics(gallicacidequivalent),FRAP(AEAC),DPPH(I%),totalFGsandtotalphenolicacidsindicatedthatAAplayedamajorrolefortheantioxidantcapacityofcitrusjuices,andphenolicsalsoplayedanimportantrole,whichmaybemainlyascribedtoFGs,whilstphenolicacidsseemedtoplayaminimalrole.Furthermore,HuyouandHybrid439wereconsideredtwovaluablevarietiesfromtheviewofantioxidantcapacityandnutrition.

Ó2007ElsevierLtd.Allrightsreserved.

Keywords:Citrusjuices;Phenolicacids;Flavanoneglycosides;Ascorbicacid;Antioxidantcapacity

1.Introduction

Citrusfruitsnotonlyhavetheirdeliciousflavorsbutalsohavetheirantioxidantcapacitywithhealthbenefits(Morton,Caccetta,Puddey,&Croft,2000;Pellegrinietal.,2003).It’swellknownthatvitaminCandcarote-noidsareabundantinsomecitrusfruits(Dhuique-Mayer,

Abbreviations:TSS,totalsolublesolids;TA,totalacidity;AA,ascorbicacid;AEAC,ascorbicacidequivalentantioxidantcapacity;HPLC–PDA,high-performanceliquidchromatography–photodiodearraydetector;F-Gs,flavanoneglycosides;FRAP,ferricreducingantioxidantpower;DP-PH,2,2-diphenyl-1-picrylhydrazyl;GAE,gallicacidequivalent.*Correspondingauthor.Fax:+8657186971165.E-mailaddress:psu@zju.edu.cn(X.Ye).0308-8146/$-seefrontmatterÓ2007ElsevierLtd.Allrightsreserved.doi:10.1016/j.foodchem.2007.06.046

Caris-Veyrat,Ollitrault,Curk,&Amiot,2005),thustheyareverybeneficialtohumanhealth.Inrecentyears,moreattentionshadbeenpaidonphenoliccompoundsofcitrusfruits,andsomepublicationshavesuggestedtheymightplayanimportantroleontheantioxidantcapacityofcitrusfruits(Gorinsteinetal.,2004a;Rapisardaetal.,1999;Wang,Cao,&Prior,1996).Dietaryphenoliccompoundsofcitrusfruitsincludeflavonoidsandphenolicacids(Bal-asundram,Sundram,&Samman,2006).Generally,FGsdominateincitrusflavonoids,whichweresummarizedrecentlybyPeterson(Petersonetal.,2006a;Petersonetal.,2006b).Furthermore,narirutin,hesperidin,naringinandneohesperidinarethemajorFGs(Rouseff,Martin,&Youtsey,1987).Ontheotherhand,phenolicacidsexist

6G.Xuetal./FoodChemistry106(2008)5–551

largelyincitrusfruitsasboundforms,whichmostlyoccurashydroxycinnamics,suchascaffeic,p-coumaric,ferulicandsinapic(Robbins,2003).Severalresearcheshavefocusedonthequantificationofphenolicacidsofcitrusfruits(Peleg,Naim,Rouseff,&Zehavi,1991;Rapisarda,Pannuzzo,Romano,&Russo,2003).Recently,somestud-ieshaveinvestigatedtheantioxidantcapacityofcitrusfruits,anditwasassumedthattotalantioxidantcapacityofcitrusfruitsweremainlyattributedtoAAandphenoliccompounds,thoughthereweresomedivergencesastowhichcompoundwasthemajorcontributor(Arena,Fal-lico,&Maccarone,2001;Caro,Piga,Vacca,&Agabbio,2004;Gardner,White,McPhail,&Duthie,2000;Rapi-sardaetal.,1999;Sun,Chu,Wu,&Liu,2002;Wangetal.,1996;Yoo,Lee,Park,Lee,&Hwang,2004).

InChina,thetotalagriculturalyieldofcitrusfruitscon-sistsofmandarins(55%),oranges(30%),pummelo(5%)andothervarieties(10%)(Ye,2005).Amongthesevenselectedmandarins,Satsuma,Ponkan,andBendizaoarethemostpopularvarietiescultivatedinChina.Further-more,HuyouisagrapefruitoriginatedfromChina(Xu,Ye,Chen,&Liu,2007),andHybrid439isarecentcitrustangorhybrid(C.reticulataÂC.sinensis)whichhadneverbeenreportedon.

TheconsumptionofprocessedcitrusjuicesinChinaisincreasingrapidlyrecently.However,notmuchworkhasbeenreportedonthestudyofantioxidantcapacityofcitrusjuiceofChina.TheobjectiveofthisstudywastoanalyzetheantioxidantcomponentsandevaluatetheantioxidantcapacityofcitrusjuicesfromselectedcitrusfruitsgrowninChina,whichwouldbeusefulforthecitrusprocessingindustryofChina.2.Materialsandmethods2.1.Materials

FifteentypicalcitrusvarietiescultivatedinChinawereselectedforthisresearch,includingsevenvarietiesofman-darins,fourkindsofsweetoranges,onelemon,onegrape-fruit,andtwopummelovarieties(Table1).TheselectedfifteencitrusvarietiesatmaturestagewereprovidedbyZhejiangCitrusResearchInstituteinHuangyancity,Zhe-jiangprovince.Citrusfruitssampleswerepeeledandsqueezedbyhandandthenjuiceyieldswerecalculated.TSSandTAofcitrusjuicesweremeasuredaccordingto

thereference(Sa

´nchez-Moreno,Plaza,DeAncos,&Cano,2003),andtotalcarotenoidweredeterminedasthemethodofWang(Wang,Chuang,&Ku,2007),respectively.2.2.Chemicals

Standardsofprotocatechuic,p-hydroxybenzoic,vanil-lic,sinapic,ferulic,caffeic,p-coumaric,narirutin,naringin,hesperidin,neohesperidin,TPTZ(2,4,6-tris(2-pyridyl)-s-triazine),2,2-diphenyl-1-picrylhydrazylradical(DPPHÁ),andFolin-Ciocalteuphenolreagentwerepurchased

fromSigma.Allotherchemicalsusedwereanalyticalgrade.

2.3.Extractionofphenolics

OnemLofcitrusjuicewasextractedwith9mLof80%methanolfor30minatroomtemperature.Aftercentrifu-gationat5000rpmfor10min,thesupernatantwastakenoutfordeterminationoftotalphenolicsbyFolin–Ciocal-teumethod,analysisofFGswascarriedoutbyHPLC,andevaluationofantioxidantcapacitybyFRAPandDPPHassay.

2.4.FGscontentdetermination

ThecontentsofFGs(narirutin,naringin,hesperidinandneohesperidin)weredeterminedbyHPLC.10lLextractwasinjectedintoaHPLCsystem,anditwasfilteredthroughamilliporemembrane(0.22lm)beforeinjection.TheanalysisutilizedaDiamonsilC18column(250Â4.6mmi.d.)usingmethanol:water:aceticacid(37:59:4)(v/v/v)asthemobilephaseataflowrateof1.0mL/minat25°Coventemperature,andtheeluentwasmonitoredat283nmforquantificationofFGs.Iden-tificationoftheFGswasaccomplishedbycomparingtheretentiontimesofpeaksinsamplestothoseofFGstan-dards.CalculationofFGsconcentration(expressedasmg/L)wascarriedoutbyanexternalstandardmethodusingcalibrationcurves.

2.5.Phenolicacidscontentdetermination

PhenolicacidsweredeterminedaccordingtoNardiniwithsomemodifications(Nardinietal.,2002).Twomillili-tercitrusjuicewasfirstlydilutedto5mLwithdistilledwater,andthenitwastreatedbyalkalinehydrolysis(5mLof4MNaOH,containing1%ascorbicacidand10mMEDTA)for4hunderanitrogenatmosphereatroomtemperature.AfteracidificationtopH2using6MHCl,itwascentrifugedat5000rpmfor10min.After-wards,phenolicacidswereextractedfromthehydrolysate3timeswithdiethylether-ethylacetate(1:l)(v/v)atasol-venttowaterphaseratioof1:l.Theether-ethylacetateextractsweredehydratedwithanhydroussodiumsulfate,filtered,andevaporatedtodrynessundervacuumat30°C.Thedryresiduesweredissolvedinto5mLmethanol.PhenolicacidsofHPLCanalyseswerecarriedoutonanAlliance2695separationsmodule(Waters)linkedsimulta-neouslytoaPDA2996(Waters).Thepreparedphenolicacidsolutionwasfilteredthroughamilliporemembrane(0.22lm)beforeinjection,and20lLwasinjectedonthereversedphasecolumn(250Â4.6mmi.d.).Thecolumnthermostatwassetat40°C.SolventAconsistedof4%ace-ticacid,andsolventBconsistedofmethanol(A:B=20:80)ataflowrateof1mL/min,whichwasinaccordancewithRaoetal.(Rao&Muralikrishna,2002)withminormodi-fications.Aftereachrunthecolumnwaswashedwith100%

G.Xuetal./FoodChemistry106(2008)5–551

Table1

Juiceyield,TSS,TA,andTSS/TAratioofcitrusjuicesVarietiesWase-SatsumaSatsumaPonkanBendizaoManju

Hybrid439Zhuhong

SkaggsbonanzaHamlin

LiubenchengYinzaochengLemonHuyouMiyouSijiyou

ab7

CommonnameMandarinMandarinMandarinMandarinMandarinMandarinMandarinSweetorangeSweetorangeSweetorangeSweetorangeLemonGrapefruitPummeloPummelo

SpeciesnameC.C.C.C.C.C.C.C.C.C.C.C.C.C.C.

unshiuvar.praecoxTanakaSatsumaunshiuMarc.

poonensisHort.exTanakasuccosaHort.exTanakatadiferaxHort.exTanakareticulataÂC.sinensiserythrosaHort.exTanaka

sinensisvar.brasiliensisTanakasinensisOsbeckcvHamlin

sinensisOsbeckcvLiubenchengsinensisOsbeckcvYinzaochenglimon(L.)Burm.f

paradisiMacf.Changshanhuyougrandis(L.)OsbeckcvMiyougrandis(L.)OsbeckcvSijiyou

Juiceyield(%)55.4652.8752.1356.8060.7442.88.0950.7943.5346.2443.40.3940.0427.5026.95

TSS(%)a11.7513.0812.0014.1710.4214.9211.5812.5812.5811.5811.3310.9210.5811.9210.33

TA(%)b0.941.061.290.961.071.870.940.861.311.201.386.111.530.700.72

TSS/TAratio12.4812.359.3314.769.758.0012.3014.639.5.628.231.796.9217.0914.44

Totalsolublesolids.Totalacidity.

methanolandequilibratedtoinitialconditionsfor15min.ThePDAdetectorwassetscanningrangefrom210to400nmwithresolutionof1.2nm.PhenolicacidswereidentifiedbytheretentiontimeandtheUV–Visspectraofstandards.Quantificationofphenolicacidswascarriedoutbyanexternalstandardmethodusingcalibrationcurves,andconcentrationofphenolicacidswasexpressedasmg/L.

2.6.AAcontentdetermination

AAwasanalyzedbyusingliquidchromatographyonanRP-PhasewithUVdetectionaccordingtoLeongandShui(Leong&Shui,2002)withsomemodifications.AAstan-dardsolution(400lg/mL)wasprepared.Thiswasthendilutedtogive40,20,10,5and2.5mg/Lworkingstandardsolutions.1mLsamplewasextractedwith9mL0.1%oxa-licacidfor3min.Thenthesamplewasimmediatelyfilteredthroughamilliporemembrane(0.45lm)beforeinjection.TheseparationwasperformedonaDiamonsilC18column(250Â4.6mmi.d.)using0.1%(v/v)oxalicacidasthemobilephaseataflowrateof1.0mL/minat25°Coventemperature,andtheeluentwasmonitoredat243nm.Theascorbicacidcontentswereexpressedhereasmg/L.2.7.Totalphenolicsdetermination

TotalphenolicsweredeterminedbytheFolin–Ciocalteumethod(Singleton,Orthofer,&Lamuela-Raventos,1999).Briefly,analiquot(1mL)ofappropriatelydiluted80%methanolextractswereaddedtoa25mLvolumetricflaskfilledwith9mLdistilledwater.AreagentblankusingddH2Owasprepared.Folin–Ciocalteuphenolreagent(0.5mL)wasaddedtothemixtureandshakenvigorously.After5min,5mLof5%Na2CO3solutionwasaddedwithmixing.Thesolutionwasimmediatelydilutedto25mLwithdistilledwaterandmixedthoroughlyandthen

allowedtostandfor60minbeforemeasurement,andtheabsorbancewasmeasuredat750nmversusthepreparedblank.Totalphenolicscontentofsamplewasexpressedasmg/Lofgallicacidequivalent(GAE).

2.8.Ferricreducingantioxidantpower(FRAP)assayTheferricreducingabilityofeachstandardsolutionwasmeasuredaccordingtoamodifiedprotocoldevelopedbyBenzieetal.(Benzie&Strain,1996).TopreparetheFRAPreagent,amixtureof0.1Macetatebuffer(pH3.6),10mMTPTZ,and20mMferricchloride(10:1:1v:v:v)wasmade.0.1mLextractwasaddedto1.9mLreagent.Readingsattheabsorptionmaximum(593nm)weretakenusingaShi-madzuUV–visible2501spectrophotometer,andthereac-tionwasmonitoredfor10min.AAsolutionwasusedtoperformthecalibrationcurves.ResultwasalsoexpressedasAEACmg/L.

2.9.DPPHfreeradical-scavengingassay

TheDPPHfreeradical-scavengingactivityofjuiceswasmeasuredusingthemethoddescribedbyGorinsteinetal.(Gorinsteinetal.,2004b).A0.1mMsolutionofDPPHinmethanolwasprepared.Analiquotof0.2mLofsamplewasaddedto2.8mLofthissolutionandkeptinthedarkfor30min.TheabilityofscavengingtheDPPHradicalwascalculatedwiththefollowingequation:%Inhibition¼½ðA0ÀA1Þ=A0󰀅Â100

WhereA0istheabsorbanceofthecontrol,A1istheabsorbanceinthepresenceofsample.2.10.Statistics

Allsampleswerepreparedandanalyzedintriplicate.Toverifythestatisticalsignificanceofallparameters,the

8G.Xuetal./FoodChemistry106(2008)5–551

valuesofmeans±S.D.werecalculated.Tocomparesev-eralgroups,analysisofvariance(ANOVA)wasused.ThePearsoncorrelationcoefficient(R)andp-valuewereusedtoshowcorrelationsandtheirsignificance(SPSSforWindows,Release11.5.0(June2002,SPSSInc.)).Proba-bilityvalueofp<0.01wasadoptedasthecriteriaforsig-nificantdifferences.3.Resultsanddiscussion

3.1.Juiceyield,TSS,TA,andTSS/TAratio

Thequalityparameters,includingjuiceyield,TSS,TA,andTSS/TAratioofcitrusjuiceswereshowninTable1.Apparently,thevaluesvariedlargelyamongcitrusvarie-ties,whereManjuachievedthehighestyield(60.74%),andSijiyouhadthelowestyield(26.96%).Hybrid439hadthehighestTSSvalue(14.92%),whereasSijiyouhadthelowestvalue(10.33%).TAvalueoflemonachievedthehighestvalue(6.11%)followedbyHybrid439(1.87%),whileMiyouhadthelowestvalue(0.70%).TheTSS/TAratiowasalsoanimportantparameter,relatedwithqualitycharacteristicsofcitrusfruits,whereMiyouhadthehighestvalueofTSS/TA(17.09),andlemonhadthelowestvalue(1.79).Fromtheabovedata,significantdifferencesbetweenspeciesandvarietieswereobserved.Amongthecitrusvarietiesselected,theHybrid439wasanewvariety,andmoreattentionwasgiventoit.3.2.ContentsofFGsandphenolicacids

FourmajorFGs(narirutin,naringin,hesperidin,neo-hesperidin)ofcitrusfruitsweredetermined(Table2).Hes-peridinandnarirutinwereconsideredasmajorFGsinmandarinandorangejuices,whereasnaringinandneohes-peridinwerenotdetectable.Formandarinandorangejuices,hesperidincontentrangedfrom304.46mg/L(Zhu-hong)to533.mg/L(Yinzaocheng),andnarirutincon-tentrangedfrom24.42mg/L(Zhuhong)to288.12mg/L(Satsuma).Ourresultswerecomparablewithseverallatestreports(Dhuique-Mayeretal.,2005;Petersonetal.,2006a;Petersonetal.,2006b;Vanamala,Reddivari,Yoo,Pike,&Patil,2006).Onlyhesperidinwasdetectedinlemonjuice,whileHuyouhadallofthefourFGswiththehighestcon-tentofnaringin(348.53mg/L),neohesperidin(265.25mg/L)andtotalFGs(746.08mg/L).Narirutinwasnotdetect-ableinMiyoujuice,andnarirutinandneohesperidinwerenotdetectableinSijiyoujuice.Generally,mandarin,orangeandgrapefruithadhighercontentofFGs,whilelemonandpummelohadlowercontent.Furthermore,asagrapefruit,HuyouhadthehighestcontentoftotalFGs(746.08mg/L),amountto359.48mg/Lasflavanoneagly-cones,whichwashigherthantheaveragevalue(270mg/kgasaglycones)ofgrapefruitsreportedbyPetersonetal.(Petersonetal.,2006a),Thereforefuturestudyandmoreattentionshouldbepaidtothisvariety.

Sevenphenolicacidswhichincludedfourcinnamicacids:caffeic,p-coumaric,ferulic,andsinapic,andthreebenzoicacids:protocatechuic,p-hydroxybenzoicandvanil-licweremeasuredbyHPLC–PDA.TheresultswereshowninTable3.Beforehydrolysis,1%ascorbicacidand10mMEDTAwereaddedtoavoidthedegradationofphenolicacidsunderalkalineconditions(Nardinietal.,2002).Gen-erally,ferulicdominatedinthecitrusjuices,withtheexcep-tionofMiyouandSijiyouwheresinapic(4.55mg/LMiyou)andp-coumaric(8.79mg/LSijiyou)werethelead-ingones,respectively.Totalphenolicacidsrangedfrom14.00mg/L(Miyou)to72.61mg/L(Liubencheng).Gener-ally,mandarin(exceptManju)andorangehadhighercon-tentofphenolicacidscomparedwithgrapefruitsandpummelos.Theresultswerelowertosomeextentwhencomparedwiththepreviousreports(Rapisarda,Carollo,Fallico,Tomaselli,&Maccarone,1998;Rapisardaetal.,2003),whichmightbecausedbythevarietydiversity.

Table2

FGscontentsofcitrusjuices(mg/L)Fruit

Wase-SatsumaSatsumaPonkanBendizaoManju

Hybrid439Zhuhong

SkaggsbonanzaHamlin

LiubenchengYinzaochengLemonHuyouMiyouSijiyou

abNarirutin169.45±0.34a288.12±3.92.63±2.6342.44±0.0443.70±0.17119.80±0.9524.42±0.01136.74±0.91102.77±2.10.49±1.0384.12±0.84nd

94.04±0.88ndnd

Hesperidin337.44±1.450.60±2.379.92±7.01417.94±10.25315.88±3.46501.44±6.73304.46±5.427.76±8.704.±0.13506.40±10.52533.±2.78237.96±0.1238.26±1.4942.17±1.2721.81±0.36

Naringinndbndndndndndndndndndndnd

348.53±0.36108.52±0.03125.79±0.80

Neohesperidinndndndndndndndndndndndnd

265.25±0.946.71±0.97nd

Datapresentedareinmeans±standarddeviation(n=3).Notdetected.

G.Xuetal./FoodChemistry106(2008)5–551

Table3

Phenolicacidcontentsofcitrusjuices(mg/L)Fruit

Wase-SatsumaSatsumaPonkanBendizaoManju

Hybrid439Zhuhong

SkaggsbonanzaHamlin

LiubenchengYinzaochengLemonHuyouMiyouSijiyou

a9

CinnamicsCaffeic2.71±0.00a2.74±0.075.24±0.045.39±0.022.±0.205.50±0.116.55±0.115.02±0.123.26±0.025.68±0.0.79±0.152.07±0.032.±0.062.02±0.047.23±0.01

p-Coumaric6.19±0.003.66±0.082.79±0.077.24±0.051.32±0.113.47±0.033.06±0.018.15±0.096.17±0.1013.49±0.1.17±0.2711.57±0.082.60±0.123.75±0.098.79±0.08

Ferulic36.49±0.0840.07±0.3726.07±0.35.00±0.0718.11±1.9216.53±0.05.91±0.2132.14±0.1539.94±0.8243.20±0.70.13±1.2035.77±0.3711.13±0.381.63±0.036.77±0.05

Sinapic2.90±0.022.78±0.043.36±0.056.05±0.072.78±0.319.12±0.204.39±0.215.09±0.297.88±0.416.83±0.076.24±0.166.75±0.153.88±0.194.55±0.143.77±0.30

BenzoicsProtocatechuic0.86±0.030.71±0.030.57±0.010.55±0.020.55±0.060.82±0.010.58±0.030.61±0.020.70±0.031.02±0.040.75±0.350.72±0.030.71±0.060.76±0.060.81±0.02

p-Hydroxybenzoic1.69±0.011.16±0.030.90±0.020.74±0.040.86±0.021.77±0.071.01±0.011.04±0.000.99±0.021.17±0.010.87±0.330.79±0.001.07±0.070.67±0.040.81±0.00

Vanillic3.40±0.062.71±0.020.94±0.050.69±0.030.94±0.033.65±0.221.39±0.051.14±0.001.17±0.011.21±0.000.87±0.630.85±0.022.86±0.200.63±0.071.17±0.00

Total.24±0.1553.83±0.6039.85±0.5765.66±0.3027.10±2.60.87±0.3062.90±0.4053.19±0.6760.10±1.4172.61±0.9662.82±3.0958.50±0.6824.79±1.0614.00±0.3529.35±0.46

Datapresentedareinmeans±standarddeviation(n=3).

3.3.Contentoftotalcarotenoid,AA,totalphenolics,andantioxidantcapacityofcitrusjuices

Totalcarotenoidwasdeterminedbycolorimetricmethod(expressedasb-caroteneequivalent),andAAcon-tentwasdeterminedbyHPLC,andtotalphenolicsweremeasuredbyFolin–Ciocalteumethod(GAE),andantioxi-dantcapacityofcitrusjuicewasevaluatedbyFRAP(AEAC)andDPPHassay(I%)(Table4).Totalcarotenoidrangedfrom0.06mg/L(Yinzaocheng)to10.02mg/L(Ben-dizao).Generally,mandarinfruitshadmuchhighercon-tentoftotalcarotenoidthansweetoranges,lemon,grapefruit,andpummelos.Itwasreportedthatmandarinfruitshadmuchhighercontentofbeta-cryptoxanthinandvitaminAthanoranges(Dhuique-Mayeretal.,2005;Melendez-Martinez,Vicario,&Heredia,2007).Also,ourresultwascomparablewithotherreports(Gardneretal.,2000;Wangetal.,2007),thoughthereweresomediver-gencesduetodifferentcitrusvarietiesinvestigated.AsforAA,mandarinjuiceshadlowerAAcontentwhencom-paredwithorangejuicesexceptHybrid439,whichwasaccordancewiththeotherreports(Dhuique-Mayeretal.,2005;Rapisardaetal.,2003).ItwasinterestingthatHybrid439achievedthehighestAAcontent(631.25mg/L)amongthefifteenselectedcitrusjuices.Furthermore,totalpheno-licsandDPPHinhibitoryofHybrid439bothachievedthehighestvalue:1555.49mg/Land61.62%,whichsuggestedthatHybrid439isavaluablevarietywithhighantioxidantcapacitythatmaybebeneficialtohealth.ForFRAPassay,Hamlinhadthehighestvalueof9.31AEACmg/L,whilelemonhadthelowestvalueof307.43AEACmg/L.Contri-butionofAAtototalantioxidantcapacitywascalculated,anditwasfoundthatAAcontributiontototalantioxidantcapacityofcitrusjuiceswasmorethan50%exceptWase-Satsuma(48.12%).Theresultswereinagreementwithpre-viousreports(Arenaetal.,2001;Caroetal.,2004;Gardner

Table4

Totalcarotenoid,AAcontents,totalphenolics,andantioxidantcapacityofcitrusjuicesFruit

Wase-SatsumaSatsumaPonkanBendizaoManju

Hybrid439Zhuhong

SkaggsbonanzaHamlin

LiubenchengYinzaochengLemonHuyouMiyouSijiyou

aTotalcarotenoid(mg/L,b-caroteneequivalent)7.26±0.069.14±0.112.92±0.2010.02±0.025.20±0.446.36±0.726.38±0.180.60±0.040.72±0.000.16±0.040.06±0.020.08±0.040.14±0.020.10±0.020.16±0.00

AA(mg/L)218.83±4.00a326.80±1.23282.68±1.08245.95±0.99234.74±1.80631.25±5.51337.20±3.69539.34±0.40623.79±5.51614.11±3.974.71±1.55233.44±2.52429.44±1.00390.57±1.22314.19±2.74

FRAP

(AEAC,mg/L)4.72±11.06598.48±14.79476.19±19.31482.98±5.70361.24±9.06875.93±11.741.14±6.59765.33±7.479.31±12.61886.26±1.72712.61±10.63307.43±14.37617.50±11.82510.16±3.99442.22±3.31

ContributionofAA(%)48.12.6159.3650.92.9872.0762.3170.4769.3669.2966.6275.9369.5576.5671.05

Totalphenolics(GAE,mg/L)863.38±12.401109.23±10.33830.32±4.13972.88±35.12774.±10.631555.49±18.591043.12±22.731173.28±20.661499.71±16.531462.52±4.731245.59±12.33751.82±13.341241.46±12.21863.38±10.801.40±5.49

InhibitionofDPPH(%)26.31±0.8733.65±0.4829.67±0.3325.39±1.7723.69±0.61.62±0.7136.75±0.8850.92±2.1260.24±0.1960.13±0.5147.82±0.7924.50±0.6639.83±2.2037.71±1.0735.79±0.95

Datapresentedareinmeans±standarddeviation(n=3).

550G.Xuetal./FoodChemistry106(2008)5–551

Table5

CorrelationcoefficientsofAA,totalphenolics(GAE),FRAP(AEAC),DPPH(I%),totalFGs,andtotalphenolicacids(n=15)

Totalphenolics

FRAPDPPHAA

TotalFGs

Totalphenolicacids

FRAP0.962*0.961*0.3*0.336

DPPHAATotalFGs

0.904*0.845*0.841*0.659*0.472

0.992*0.4590.227

0.40.185

0.341

*Correlationissignificantatthe0.01level(2-tailed).

etal.,2000;Yooetal.,2004),whichsuggestedAA,notphenoliccompounds,wasthemajorcontributoroftotalantioxidantcapacityofcitrusjuices.However,somestud-iessuggestedphenoliccompoundsdominatedtotalantiox-idantcapacityofcitrusfruits(Rapisardaetal.,1999;Sunetal.,2002;Wangetal.,1996).Itseemedthatsomefactorssuchasthedifferentcitrusvariety,maturity,materialprep-arationandanalyzingmethodsmightcausethedivergence.Generally,orangehadhigherantioxidantcapacitythanothercitrusvarietiesduetoitshigherAAcontent.3.4.CorrelationcoefficientsofAA,totalphenolics(GAE),FRAP(AEAC),DPPH(I%),totalFGs,andtotalphenolicacids

CorrelationcoefficientsofAA,totalphenolics(GAE),FRAP(AEAC),DPPH(I%),totalFGs,andtotalphenolicacidswereshowninTable5.AAcontentcorrelatedhighly(p<0.01)withtotalphenolics,FRAP(AEAC)andDPPH(I%),whichmeantthatAAplayedamajorrolefortheantioxidantcapacityofcitrusjuices.TotalFGscorrelatedhighly(p<0.01)withtotalphenolicsandFRAP(AEAC),butcorrelationwithDPPH(I%)wasnotsignificant,whichindicatedthatFGsplayedaminorrolefortheantioxidantcapacityofcitrusjuices.AsFGsarethemajorphenoliccompounds,theyobviouslypresentahighcorrelationwithtotalphenolics.CorrelationcoefficientsoftotalphenolicacidswithFRAP(AEAC)andDPPH(I%)werenotsignif-icant,whichdemonstratedthatphenolicacidsplayedaminimalroletotheantioxidantcapacityofcitrusjuices.4.Conclusion

BasedonthecorrelationcoefficientsofAA,totalphen-olics(GAE),FRAP(AEAC),DPPH(%),totalFGs,andtotalphenolicacids,AAplayedamajorroleintheantiox-idantcapacityofcitrusjuices;phenolicsalsoplayedanimportantrole.Phenolicacidsseemedtoplayaminimalrole.Whenconsideringantioxidantcapacity,orangewouldbemoresuitableforjuiceprocessingthanothervarietiesduetotheirhighcontentofAA.Hybrid439(tangor)achievedseveralhighestvaluesinourstudy,andHuyou(grapefruit)hadthehighestFGscontent.ThesetraitsofHybrid439andHuyoumadethemvaluablefromanutri-tionalandhealthbenefitspointofview.Therefore,Hybrid439andHuyoumaybeconsideredasexcellentsourcesofphytochemicalswithpotentialhealthbenefits.

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