Active film from chitosan incorporating green tea extract for shelf life extension of pork sausages

FoodHydrocolloids27(2012)102e108

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FoodHydrocolloids

journalhomepage:http://wendang.chazidian.com/locate/fo

odhyd

Active?lmfromchitosanincorporatinggreenteaextractforshelflifeextensionofporksausages

UbonratSiripatrawan*,SuparatNoipha

DepartmentofFoodTechnology,FacultyofScience,ChulalongkornUniversity,Patumwan,Bangkok10330,Thailand

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Articlehistory:

Received15February2011Accepted18August2011Keywords:

ActivepackagingChitosan?lm

GreenteapolyphenolsShelflife

AntimicrobialAntioxidant

abstract

Chitosan?lmincorporatinggreenteaextract(CGT-?lm)wasusedasactivepackagingforshelflifeextensionofporksausages.Thephysical,chemical,microbiological,andsensoryqualitiesofporksausageswrappedwithCGT-?lmwerecomparedwiththosewrappedwithchitosan-alone?lm(C-?lm)andthosewithoutchitosan?lmwrapping(control).Changesinthequalitiesofporksausagesincludingcolor,texture,lipidoxidationwithrespecttothiobarbituricvalue(TBA),andmicrobiologicalqualitiesincludingtotalplatecounts,yeastsandmolds,andlacticacidbacteriaweredeterminedthroughoutthestorageat4??C.Thesensoryqualitiesincludingodor,color,slimeformation,andoverallacceptabilitywereevaluatedusingQuantitativeDescriptiveAnalysis.ItwasfoundthatsampleswrappedwithCGT-?lmshowedlowerchangesincolor,texture,TBAvalue,microbialgrowth,andsensorycharacteristicsthanthosewrappedwithC-?lmandcontrol,respectively.Successfulinhibitionoflipidoxidationandmicrobialgrowthintherefrigeratedporksausageswaspossiblewithchitosan?lmincorporatinggreenteaextract.Theresultssuggestedthatincorporationofgreenteaextractintochitosan?lmcouldenhancetheantioxidantandantimicrobialpropertiesofthe?lmandthusmaintainedthequalitiesandprolongedtheshelflifeofthesausages.

Ó2011ElsevierLtd.Allrightsreserved.

1.Introduction

Activepackaging,thenewgenerationoffoodpackaging,isgaininginterestfromresearchersandindustryduetoitspotentialtoprovidefoodqualityandsafetybene?ts.Duetotheconsumerconcernsaboutfood-relatedhealthrisksandenvironmentalproblems,currentresearchinactivepackaginghasfocusedontheuseofnaturalpreservativesinbiodegradablepackagingmaterials(Suppakul,Miltz,Sonneveld,&Bigger,2003;Yingyuadetal.,2006).Favorableactivepackagingsystemsarebasedontheincorporationofnaturalantimicrobialand/orantioxidativesubstancesinfoodpackagingmaterialsinordertocontrolundesirablechangesoffoodqualities(Dutta,Tripathi,Mehrotra,&Dutta,2009;Fernandez-Saiz,Lagaron,&Ocio,2009;Salgado,Fernández,Drago,&Mauri,2011).

Chitosan,alinearpolysaccharideofrandomlydistributedb-(1-4)-linkedD-glucosamineandN-acetyl-D-glucosamine,isafunctionalbiopolymerobtainedfromdeacetylationofchitin.Chitosanisnon-toxic,biocompatible,andbiodegradableandthusisconsideredasanenvironmentallyfriendlypackagingmaterial(Caner&Cansiz,2007;Caner&Cansiz,2008;Fernandez-Saizetal.,2009;Pereda,

*Correspondingauthor.Tel.:þ6622185536;fax:þ6622544314.E-mailaddress:ubonratana.s@chula.ac.th(U.

Siripatrawan).0268-005X/$eseefrontmatterÓ2011ElsevierLtd.Allrightsreserved.doi:10.1016/j.foodhyd.2011.08.011

Ponce,Marcovich,Ruseckaite,&Martucci,2011).Chitosanhasbeenusedasantimicrobial?lmsandcoatingsduetoitseffectivenessofinhibitingthegrowthofnotonlyGram-positiveandGram-negativebacteriabutalsoyeastsandmolds(Chen,Yeh,&Chiang,1996).Chitosanantimicrobialactivitycomesfromitspositivechargesthatwouldinterferewiththenegativelychargedresiduesofmacromol-eculesonthemicrobialcellsurface,causingthemembraneleakage(Duttaetal.,2009;Peredaetal.,2011).Duetoitsintrinsicantimi-crobialpropertiesandgood?lm-formingability,chitosancanbeusedasactiveantimicrobial?lms(Fanetal.,2009;Hernández-Muñoz,Almenar,Valle,DelVelez,&Gavara,2008).

Incorporationofantimicrobialand/orantioxidativesubstancesintopackagingmaterialshasbecomepopularsincemicrobialspoilageandoxidationaremajorproblemsaffectingfoodquality.Thisapproachcanreducetheadditionoflargeamountsoffoodadditivesthatareusuallyincorporatedintofood.Duetothepotentialhealthriskscausedbysyntheticactivecompounds(Gómez-Estaca,Gimnez,Montero,&Gómez-Guillén,2009),extensiveresearchhasbeenconductedtoemploysomenaturalactivecompoundsasalternativestosyntheticantioxidants,includingincorporationofa-tocopherolinto?shskingelatin?lms(Jongjareonrak,Benjakul,Visessaguan,&Tanaka,2008),additionoftetrahydrocurcuminoidsintochitosan?lms(Portes,Gardrate,Castellan,&Coma,2009)anduseofantioxi-dantborageextractingelatin?lms(Gómez-Estacaetal.,2009).

U.Siripatrawan,S.Noipha/FoodHydrocolloids27(2012)102e108103

Greentea(Camelliasinensis)isagoodsourceofpolyphenoliccompounds(Chan,Lim,&Chew,2007).Catechins(alsoknownas?avanols),includingepicatechin(EC),epigallocatechin(EGC),epi-catechingallate(ECG),epigallocatechingallate(EGCG),catechin(C),gallocatechingallate(GCG),catechingallate(CG),andgalloca-techin(GC),arethedominantphenoliccompoundsintealeaves.Besides?avanols,various?avonols,suchasquercetin,kaempferol,andquercetagetin,and?avones,suchasrutinandchrysin,arealsopresentintealeaves(Chanetal.,2007;Yilmaz,2006).Greenteapolyphenolshavebeenreportedtoactasfreeradicalscavengerstoterminatetheradicalchainreactionsthatoccurduringtheoxida-tionoftriglyceridesinfoodsystems(Bozkurt,2006;Perumalla&Hettiarachchy,2011),andhasshowninhibitoryeffectsinvitroagainstfoodspoilageandpathogenicmicroorganismsincludingListeriamonocytogenes,EscherichiacoliO157:H7,Salmonellatyphi-murium,Staphylococcusaureus,Shigella?exneri,andVibriocholerae(Hamilton-Miller,1995;Perumalla&Hettiarachchy,2011).

Cookedporksausage,aready-to-eatmeatproductwidelyconsumedinThailand,ispronetospoilagebybothmicrobialcontaminationandlipidoxidation,causingfoodbornediseasesandunacceptableorganolepticcharacteristics.Therefore,preventingbacterialgrowthanddelayinglipidoxidationcanpromotetheextensionofshelflife.Ourpreviousstudyhasshownthataprom-isingactivechitosan-based?lmcouldbeachievedbyincorporationwithgreenteaextract,asanaturalactiveagent,toimproveitsantimicrobialandantioxidantproperties(Siripatrawan&Harte,2010).Therefore,thisresearchwasaimedtodeterminethefeasi-bilityofusingthedevelopedchitosan?lmincorporatinggreenteaextractasactivepackagingtoextendshelflifeofporksausages.2.Materials&methods2.1.Materials

Commercialfoodgradechitosanwithamolecularweightof100kDaanddeacetylationdegreeof95%waspurchasedfromSeafreshIndustryPublicCompanyLimited(Chumphon,http://wendang.chazidian.commercialgreentealeaveswerepurchasedfromalocalhyper-marketinBangkok.Greenteaaqueousextractsolutionwaspreparedbymixinggroundteaindistilledwater(1:5w/v),controlledat90??Candshakenat100oscillation/minfor10min.Polyphenoliccompoundsinthegreenteaaqueousextract(Fig.1)weredeterminedusinghighperformanceliquidchromatography(HPLC),equippedwitha5mm,250Â4.6mmidC18separationcolumnandaphotodiodearraydetector(VarianInc.Scienti?cInstruments,PaloAlto,USA)followingthemethodofSiripatrawan,Pongamphai,Douglas,andHarte(2008).PlateCountAgar,PotatoDextroseAgar,andLactobacillusMRSAgarwereobtainedfromHiMediaLaboratoriesPvt.Limited(Bombay,India).Hydrochloricacid,2-thiobarbituricacid,aceticacid,andglycerolwereobtainedfromSigmaeAldrich(SigmaChemicalCo.,St.Louis,MO,USA).2.2.Filmpreparation

Chitosan?lm-formingsolution(2%w/v)waspreparedaccordingtotheprocedureofSiripatrawanandHarte(2010)bydissolvingspeci?camountofchitosanpowderinto1%aceticacidsolutionandglycerolattheconcentrationof30%w/wofchitosanpowderwasusedasplasticizer.Thegreenteaaqueousextractsolutionwasthenmixedwithchitosansolutiontoobtainthe?nalconcentrationsof20%(w/v)ofgreenteainthechitosan?lm-formingsolution.Theresultingsolutionwashomogenizedusingahomogenizer(D-79282,YstralGmbH,Ballrechten-Dottingen,Germany)andwassubsequentlydegassedtoremoveairbubblesusingasonicator(UltrasonicProcessor,Cole-Parmer,VernonHills,Illinois,USA).Each?lm-forming

Fig.1.HPLCchromatogramofaqueousgreenteaextract:1,gallicacid;2,EGC;3,catechin;4,EGCG;5,EC;6,rutin;7,ECG;8,quercetin;9,kaempferol.

solution(90g)wascastona12Â28.5cm2ceramicplateanddriedatambienttemperature(26??C).Theobtained?lmswereconditionedinanenvironmentalchamberat25??Cand50%relativehumidity(RH)for48hbeforeused.2.3.Samplepreparation

Cookedporksausageswereobtainedfromalocalmeatpro-cessingplantontheinitialdayofmanufacture.Thesausagescon-tained61.43Æ0.93%moisture,18.94Æ0.86%fat,16.26Æ0.78%protein,and2.12Æ0.31%ash.Chitosan-alone?lm(C-?lm)andchitosan?lmcontaininggreenteaextract(CGT-?lm)wereusedtowraparoundthesausages.Thesampleswithoutchitosan?lmwrappingwereusedascontrol.Eachsamplewasindividuallypackagedintoa8Â12cmpouchof85mmlinearlowdensitypolyethylenecoatedwithpolyamideplasticbagunderatmosphericconditionsandheat-sealedusinganimpulsesealer.Allsampleswerestoredat4Æ1??Candwereanalyzedondays0,4,8,12,16,and20(onlyCGT-?lmwrappedsampleswerestoreduptoday24).Thesausagesampleswereanalyzedimmediatelyafteropeningthepackagesandremovingthewrappedchitosan?lms.Allmeasure-mentswereconductedonthreeseparatesamplesinduplicate.2.4.Microbiologicalanalysis

Twenty?vegramsofporksausageswerehomogenizedin225mlof0.1%peptonebufferfor2minusingaStomacherLabBlender(SewardLaboratory,London,UK).Serialdecimaldilutionsweremadewiththesamediluent.Thesampleswerespread-platedonPlateCountAgarandincubatedat37??Cfor24hfortotalviablecounts.Foryeastsandmolds,thesampleswerespread-platedonPotatoDextroseAgarandincubatedat25??Cfor72h.Forlacticacidbacteria,thesampleswerepour-platedonLactobacillusMRSAgarandincubatedat37??Cfor72h,followingthemethodofBingolandBostan(2007).2.5.Lipidoxidation

Thiobarbituricacid(TBA)measurementwasdeterminedfollowingthemethodofTarladgis,Watts,andYounathan(1960).Tengramsofhomogenizedsamplewereaddedwith97.5mlofdistillatedwaterand2.5mlof4NHCl.Themixturewasheatedwithsteamdistillation.Fivemlofdistillatewasaddedto5ml

of

104U.Siripatrawan,S.Noipha/FoodHydrocolloids27(2012)102e108

thiobarbituricreactivereagentcontaining0.02MTBAin90%glacialaceticacidandincubatedinboilingwaterfor35min.Aftercooling,theabsorbanceofthepinksolutionwasmeasuredat538nmusingaspectrophotometer(ThermoScienti?cGENESYS20,ThermoFisherScienti?c,Inc.,Rochester,NY,USA).Theconstant7.8wasusedtocalculatetheTBAnumberusingEq.(1).TheTBAvalueisexpressedasmilligramsofmalonaldehydeperkgofsample.

TBAvalue¼7:8Abs538

(1)

2.6.Colormeasurement

CIELABcolor(L*,a*,b*)valuesweremeasuredusingaMinoltaChromameter(CR-300,MinoltaCameraCo.,Japan)witha10mmdiameterapertureanda10??standardobserver.ThevaluesforL*(lightness),a*(redness),andb*(yellowness)wererecordedtoevaluatesurfacecolorchangesofporksausagesduringstorage.2.7.Texturemeasurement

Thetexture(cuttingforce)wasmeasuredusingaTextureanalyzer(LloydFoodTextureAnalyzer,modelTA500,England)withadisplacementspeedof2mm/s(Rao&Henrickson,1983).Theforcenecessarytoobtainaconstantdeformationof30mmwasrecordedingramforce.2.8.Sensoryevaluation

Thesampleswereevaluatedbyanexperiencedten-memberpanel.Panelistswerechosenonthebasisofpreviousexperienceinconsumingporksausages.Furthermore,apreparatorysessionwasheldpriortotestingsothateachpanelmembercouldthor-oughlydiscussandclarifyeachattributetobeevaluated.Testingwasinitiatedafterthepanelistsagreedonthespeci?cations.Thesausageswerebroughttoapproximately25??Cbeforeassessment.QuantitativeDescriptiveAnalysiswasusedtoobtainfourattributestodescribethesamples.Odorattributeswereassessed?rst,fol-lowedbyappearance(colorandslime)andoverallacceptability.Thesensoryevaluationwasclassi?edintotenstages:odor(9¼extremelydesirable;5¼slightoff-odor;0¼extremelyunac-ceptable);discoloration(0¼nodiscoloration;5¼slightdiscolor-ation;9¼extremelyunacceptable),slimeformation(0¼noslimeformation;5¼slightslimeformation;9¼extremelyunaccept-able),andoverallacceptability(9¼extremelydesirable;5¼slightlyunacceptable;0¼extremelyunacceptable).2.9.Statisticalanalysis

SymmetricFactorialExperimentwithCompletelyRandomizedDesign(CRD)wasusedforcolor,texture,andTBAmeasurementsoverthestorageperiod.RandomizedCompleteBlockDesignwasusedforassessmentofsensoryevaluation.Thestatisticalsigni?-canceofdifferencesbetweenmeanvalueswasestablishedatp 0.05withtheDuncan’sNewMultipleRangeTestinthegeneralmodeloftheSPSSstatisticalpackage(SPSSInc.,Chicago,Illinois).3.Resultsanddiscussion3.1.Microbiologicalanalysis

Table1isshowntotalcounts,yeastsandmolds,andlacticacidbacteriaofporksausagesduringstorageat4??C.Controlsausagesampleswerefoundtohavehigherpopulationoftotalaerobiccounts,yeastsandmolds,andlacticacidbacteria.These

Table1

Totalcount,yeastsandmolds,andlacticacidbacteria(LogCFU/g)aofporksausagesduringstorageat4??C.StorageSamplesTotalcountYeastsandLacticacidtime(days)moldsbacteria0

Control<1NDNDC-?lm<1NDNDCGT-?lm<1

NDND4

Control2.55Æ0.03eND<1C-?lm<1NDNDCGT-?lm<1

NDND8

Control2.62Æ0.06e<1<1C-?lm<1<1<1CGT-?lm<1

<1

ND

12

Control5.24Æ0.18c3.57Æ0.10d2.52Æ0.07cC-?lm1.11Æ0.16f1.01Æ0.11f<1CGT-?lm<1

<1

<1

16

Control6.54Æ0.02b4.35Æ0.10c3.03Æ0.04bC-?lm2.27Æ0.36e2.84Æ0.14e<1CGT-?lm1.14Æ0.21f1.24Æ0.28f<1

20

Control9.01Æ0.15a6.72Æ0.02a3.66Æ0.10aC-?lm3.64Æ0.17d5.04Æ0.08b1.25Æ0.26dCGT-?lm

2.52Æ0.09e

3.17Æ0.23e

1.02Æ0.21d

ND¼notdetected.aef

Meanswithincolumnshavingthesamesuperscriptdonotdiffersigni?cantly(p>0.05).a

DatarepresentmeanÆstandarddeviationofthreereplications.

microorganismsareconsideredasspoilagemicro?http://wendang.chazidian.comcticacidbacteriaareidenti?edasspoilagebacteriaofsausagesandotherprocessedmeatsstoredatrefrigeratedtemperatures(Ambrosiadis,Soultos,Abrahim,&Bloukas,2004;Yingyuadetal.,http://wendang.chazidian.comcticacidbacteriamaycausesouring,slimyand/orgreeningandcanproducelacticacid,ethanolandshort-chainfattyacidswhichcontributetooff-odors(Samelis,Kakouri,&Rememtzis,2000).Thepopulationofyeastsandmoldswasalsorelativelyhigh,whichmaycausetheslimeformationonthesausagesurface.Themicrobialgrowthwasmorerapidinthecontrolsampleswherethetotalviablecountof5.24LogCFU/gwasfoundonday12.Atthispoint,thecontrolsampleshadoff-odoranddiscolorationandwouldhavebeenrejectedbytheconsumers.

Whencomparedwithcontrolsamples,sampleswrappedwithC-?lmhadlowervariabilityoftotalaerobiccounts,yeastsandmolds,andlacticacidbacteria.Thisresultsuggestedthatchitosan?lmcouldinhibitmicrobialgrowthinthesausages.Theantimi-crobialeffectofchitosanisthoughttoberelatedtoelectrostaticinteractionbetweenapositivechargeontheNHþ3groupofglucosaminemonomerinchitosanmoleculesandnegativechargeofmicrobialcellmembranethatleadstotheleakageofintracellularconstituents(Duttaetal.,2009).Incorporationofchitosan?lmwithgreenteaextractenhancedtheantimicrobialpropertiesofthe?lm,astotalaerobiccounts,yeasts,andmoldsinthesausageswrappedwithCGT-?lmwerelowerthanthosewrappedwithC-?lm.Theeffectwasparticularlyevidentonday12andthereafter.However,nosigni?cantdifferenceforlacticacidbacteriacountswasobservedbetweensampleswrappedwithC-?lmandCGT-?lm.TheenhancedantimicrobialactivityofCGT-?lmispotentiallyattributedtogreenteapolyphenolswhicharecapableofbacteri-cidalactivity(Yilmaz,2006),byinhibitionofDNAandRNAsynthesisofbacterialcells(Mori,Nishino,Enoki,&Tawata,1987),inhibitionofcytoplasmicmembranefunctionofbacteria(Tsuchiya,Sato,&Iinuma,1994),andinterferingwithenergymetabolismsofbacteria(Haraguchi,Tanimoto,Tamura,Mizutani,&Kinoshita,

U.Siripatrawan,S.Noipha/FoodHydrocolloids27(2012)102e108105

1998).TheresultsaresupportedbythoseofWuetal.(2007)whofoundthatepicatechinandcaffeineingreenteacouldinhibitS.aureus,Bacillussubtilis,andE.coli,aswellasHamilton-Miller(1995)whoreportedthatphenoliccompoundsingreenteacouldinhibitE.coli,S.typhimurium,L.monocytogenes,S.aureus,andCampylobacterjejuni.Yam,Shah,andHamilton-Miller(1997)sug-gestedthattheantibacterialactivityofgreenteaextractscanbeexplainedbyitscontentofEGCG,ECG,GC,andEGC.Moreover,quercetinandkaempferolshowedactivityagainstgram-positivebacteriaandphytopathogenicfungi(Hamilton-Miller,1995).3.2.Lipidoxidation

Lipidoxidation,withrespecttoTBAvaluesofcontrolsausagesamplesandthosewrappedwithC-?lmandCGT-?lmisshowninFig.2.Duringthestorage,signi?cantlyhigher(p 0.05)TBAwasevidentincontrolsamplesthanthosewrappedwithC-?lmandCGT-?lm,respectively.Thisresultsuggestedthatlipidoxidationinsausagesamplescouldbeminimizedbytheuseofchitosan?lmprobablyduetotheantioxidantactivityofchitosan(Park,Je,&Kim,2004)aswellasitslowoxygenpermeabilitycharacteristic(Xu,Kim,Hanna,&Nag,2005).TheantioxidantabilityofC-?lmisthoughttobeduetochelationoffreeionwhichisreleasedfromhemoproteinsofmeatduringstorage(Shahidi,Arachchi,&Jeon,1999).

Incorporationofgreenteaintochitosan?lmenhancedtheantioxidantpropertiesofthe?lm,asTBAvaluesofCGT-?lmwrappedsampleswerelowerthanthosewrappedwithC-?lm.Teaextractsarepowerfulantioxidants,mainlyowingtothepres-enceofC,EC,EGC,ECG,EGCG,GCG,CG,andGC,whichareeffectivefreeradicalscavengersandmetalchelation(Chanetal.,2007;Farhoosh,Golmovahhed,&Khodaparast,2007).Theantioxidantactivitiesoftheinferredgreenteapolyphenolshavebeenattrib-utedtoassortedmechanisms,includingpreventionofradicalchaininitiation,bindingoftransitionmetalioncatalysts,andinteractionwiththefreeradicalstoinhibitlipidoxidation(Farhooshetal.,2007;Perumalla&Hettiarachchy,2011).3.3.Color

ColorvaluesincludingL*coordinate(lightnessindicator),a*value(indicatorofthetendencytowardtheredfora*positiveorgreenfora*negative)andb*value(indicatorofthetendencytowardyellowforb*positiveorblueforb*negative)ofcontrolporksausagesamplesandthosewrappedwithC-?lmandCGT-?lmduringstorageat4??CareshowninFig.3.

Fig.2.TBAvaluesofcontrolporksausagesamplesandthosewrappedwithC-?lmandCGT-?lmduringstorageat4??C.ValuesaregivenasmeanÆstandard

deviation.

Controlsamplesshowedsigni?cantlyhighervalues(p 0.05)ofL*

andb*valuesduringstoragethanthosewrappedwithC-?lmandCGT-?lm,respectively.Asigni?cantincreaseinL*andb*valuesofcontrolsamplesindicateddiscoloration.Thecolorofcontrolsamplesbecamegrayish(anincreaseinlightnessandadecreaseinredness)withanincreaseinstorageperiod.Changesfoundincolorvaluesofcontrolsampleswereprobablyduetolipidoxidationandmicrobialspoilage.Anaccumulationofhydrogenperoxideproducedbylacticacidbacteriaduringstorage(Cayré,Garro,&Vignolo,2005)maypossiblybeoneofthemainfactorsrespon-siblefordiscolorationofcontrolsamples.Theproducedperoxidecanreactwithnitricoxidehemochromogenornitricoxidemyoglobinandgiveoxidizedporphyrin,resultingingreeningofthemeatproducts(Jjaberg,Haugum,&Murmi,1970).

SampleswrappedwithC-?lmshowedlowerchangesincolorvaluesprobablyduetotheantioxidantandantimicrobialpropertiesofthechitosan?lm.Chitosanhasbeenreportedtoinhibitthegrowthofvariouspathogenicbacteria,yeastsandmolds(Chenetal.,1996),aswellaslacticacidbacteria(Comaetal.,2002),whicharepredominantincookedandcuredmeat(Samelisetal.,2000).TheresultsalsoshowedthatsampleswrappedwithCGT-?lmhadsigni?cantlylowerchanges(p 0.05)inL*andb*valuesthanthosewrappedwithC-?lm,probablyduetothe

antioxidant

Fig.3.ColorvaluesofcontrolporksausagesamplesandthosewrappedwithC-?lmandCGT-?lmduringstorageat4??C:(a)L*value;(b)a*value;(c)b*value.ValuesaregivenasmeanÆstandarddeviation.

106U.Siripatrawan,S.Noipha/FoodHydrocolloids27(2012)102e108

3.4.Texture

TextureofcontrolsamplesandthosewrappedwithC-?lmand

CGT-?lmduringstorageat4??CisshowninFig.4.Cuttingforceof

controlsampleswassigni?cantlylowerthanothersamples

throughoutthestorage.Thisisprobablybecausethegrowthof

spoilagemicroorganismsinthesausagesamples.Nosigni?cant

(p>0.05)differencebetweensampleswrappedwithC-?lmand

CGT-?lmwasobservedthroughoutthestorageperiod.Samples

wrappedwithC-?lmandCGT-?lmshowedlower(p 0.05)

changesincuttingforcethancontrolsamplesduetoantimicrobial

propertiesofthe?lmstoinhibitthegrowthofgram-positiveand

gram-negativebacteria,yeasts,andmolds(Shahidietal.,1999).

Fig.4.Texture(cuttingforce)ofcontrolporksausagesamplesandthosewrappedwith

C-?lmandCGT-?lm.ValuesaregivenasmeanÆstandard

deviation.3.5.Sensoryevaluation

Meansofsensoryattributescoresincludingodor,discoloration,

slimeformationandoverallacceptanceofcontrolporksausage

samplesandthosewrappedwithC-?lmandCGT-?lmduring

storageat4Æ1??CareshownFig.5.Thesensoryevaluation

resultsappearedtobecorrelatedtocolorindex,texture,TBAvalues,

andmicrobiologicalanalyses.

Thesensoryevaluationresultsshowedthatodorscoresdecreased

withincreasingstorageperiod(Fig.5a).Off-odoroccurredin

controlandantimicrobialeffectsofpolyphenoliccompoundsfromgreentea,includingEC,EGC,ECG,EGCG,C,GCG,CG,andGC(Chanetal.,2007;Farhooshetal.,2007;Yilmaz,2006).Theresultssuggestedthatincorporationofgreenteaintochitosan?lmcouldenhancetheantioxidativeandantimicrobialpropertiesofthe?lmandthusmaintainedthequalitiesofthesausagesamples.

Fig.5.SensoryevaluationofcontrolporksausagesamplesandthosewrappedwithC-?lmandCGT-?lmduringstorageat4??C:(a)odorscores;(b)discolorationscores;(c)slimeformationscores;(d)overallacceptancescores.