Effect of cellulose fibers addition on the mechanical proper

Information about biocomposites based on thermoplastic

FoodHydrocolloids23(2009)1328–1333

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FoodHydrocolloids

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http://doc.guandang.net/locate/foodhyd

Effectofcellulose bersadditiononthemechanicalpropertiesandwatervaporbarrierofstarch-based lms

¨llera,b,Joa oBorgesLaurindob,*,FabioYamashitaaCarmenM.O.Mu

ab

DepartmentofFoodScienceandTechnology,StateUniversityofLondrina,Londrina,PR,Brazil

DepartmentofChemicalandFoodEngineering,FederalUniversityofSantaCatarina,Florianopolis,SC88040-900,Brazil

articleinfo

Articlehistory:

Received2October2007

Accepted12September2008Keywords:Starch lmsCelluloseFibers

MechanicalWater

Permeability

abstract

Starch-based lmshavepromisingapplicationonfoodpackaging,becauseoftheirenvironmentalappeal,lowcost, exibilityandtransparency.Nevertheless,theirmechanicalandmoisturebarrierpropertiesshouldbeimproved.Theaimofthisworkwastoenhancethesepropertiesbyreinforcingthe lmswithcellulose bers.Besides,thein uencesofboththesolubilitycoef cientofwaterinthe lms(b)andthediffusioncoef cientofwatervaporthroughthe lms(Dw)onthe lms’watervaporpermeability(Kw)wereinvestigated.Filmswerepreparedbytheso-calledcastingtechnique,from lm-formingsuspen-sionsofcassavastarch,cellulose bers(1.2mmlongand0.1mmofdiameter),glycerolandwater.Thein uenceof bersadditiononKwwasdeterminedatthreerelativehumiditygradientranges,DRH(2–33%,33–64%and64–90%).Filmsreinforcedwithcellulose bersshowedhighertensilestrengthandlowerdeformationcapacity,andpresentedlowerKwthan lmswithout bers.KwshowedstrongdependencyofbandDw,presentingvaluesupto2–3timesgreateratDRH¼64–90%thanatDRH¼33–64%,dependingonthe lmformulation.Therefore,addingcellulose berstostarch-based lmsisaviablealternativetoimprovetheirmechanicalandwaterbarrierproperties.Besides,thisworkshowedtheimportanceofdetermining lm’swatervaporpermeabilitysimulatingtherealenviron-mentalconditionsthe lmwillbeused.

Ó2008ElsevierLtd.Allrightsreserved.

1.Introduction

Starchproductionandindustrializationrepresentagoodalter-nativefordevelopingcountries(FAO,2007).Developingnewproductsfromthisrawmaterialcanaddvalueandexpanditsindustrialuse.Theproductionofbiodegradableandedible lmsfromcarbohydratesandproteinsaddsvaluetolowcostrawmaterialsandcanplayanimportantroleinfoodpreservation

´rous,Fringant,&Moro,2001;Gennadios,2002;Krochta&(Ave

Miller,1997,amongothers).Preparingthese lmsinvolvestheuseofatleastone lm-formingagent(macromolecule),asolventandaplasticizer.Themostusedmacromoleculesarepolysaccharidesandtheirderivatives,proteinsandlipids(Cuq,Gontard,&Guilbert,1998;Krochta,2002;Krochta&Mulder-Johnston,1997).

Severalstudiesreportedtheuseofstarchesfromdifferentsourcestoprepare lmsandcoatingswithdifferentproperties,andhadindicatedthatthesecarbohydratesarepromisingmaterialsin

´rousetal.,2001;Larotonda,Matsui,Sobral,&thisregard(Ave

´a,Martino,&Zaritzky,Laurindo,2005;Mali,Grossmann,Garc

*Correspondingauthor.Tel.:þ554837219448;fax:þ554837219687.

E-mailaddress:joao@enq.ufsc.br(J.B.

Laurindo).0268-005X/$–seefrontmatterÓ2008ElsevierLtd.Allrightsreserved.doi:10.1016/j.foodhyd.2008.09.002

2005;Mali,Sakanaka,Yamashita,&Grossmann,2005).However, lmsformedfromstarcharebrittleanddif culttohandle.Plasti-cizersarenormallyaddedtothe lm-formingsolutionbeforecastinganddryingprocedures,asawaytoovercome lmsbrit-tleness.Unfortunately,plasticizersgenerallydecreasethe lmwatervaporpermeability(Gontard,Guilbet,&Cuq,1993;Krochta&Mulder-Johnston,1997;Muller,Yamashita,&Laurindo,2007).

Inordertoimprovestarch-based lmcharacteristics,manyresearchesreportedresultsontheadditionofnatural bersasasuitablereinforcingcomponentforthermoplasticmaterials.Mostoftheseworksfocusedon lms’mechanicalpropertiesandhaveshowedthat bersincorporationincreases lms’tensilestrengthandelasticitymodulusanddecreasestheirelongationcapacity

´rousetal.,2001;Curvelo,deCarvalho,&Agnelli,2001;(Ave

Dufresne&Vignon,1998;Follain,Joly,Dole,Roge,&Mathlouthi,

´spar,Benko´,Dogossy,Re´czey,&Cziga´ny,2005;Ma,Yu,&2006;Ga

Kennedy,2005).

Concerningtothebarrierproperties,DufresneandVignon(1998)andFunke,Bergthaller,andLindhauer(1998)reportedthattheadditionof bersdecreasedthewatervaporpermeability(Kw)ofstarch-based lms.Thisbehaviorwasattributedtothelowhygroscopicityofcellulose bers.Infact,thebehaviorofKwdependsonthesimultaneouseffectofwaterdiffusivityinthe

Information about biocomposites based on thermoplastic

¨lleretal./FoodHydrocolloids23(2009)1328–1333C.M.O.Mu1329

polymericmatrix(Dw)andofthesolubilitycoef cientofwaterin

the lm(b)(Krochta&Miller,1997;Larotondaetal.,2005;Mulleretal.,2007).Larotondaetal.(2005),workingwithKraftpaperimpregnatedwithstarchacetate,investigatedthein uenceofthisimpregnationontheKw,Dwandbvaluesofthesematerials.Thebvaluewascalculatedthroughthe rstderivativeofthe lmwatersorptionisotherminrelationtothewateractivity(aw),pidedbythewatervaporpressure(atthesorptionisothermtemperature).As lm’sKwisproportionaltotheproductofbandDw,thevaluesofDwweredeterminedfromKwandbvalues,atthreerelativehumiditygradientranges.

Moore,Martelli,Gandolfo,Sobral,andLaurindo(2006)studiedthein uenceofbandDwonthewatervaporpermeabilityofkeratin lmsplasticizedwithglycerolandreportedthattheKwvalueincreasedalmostsixtimeswhen0.09gglycerol/gkeratinwasadded.Thisresultwasexplainedbythehighincreaseofb,whileDwdidnotchangesigni cantly.Variabilityinthe lmthicknessanddensitywerealsoreportedasin uencingthevaluesofKwofkeratin lms.Mulleretal.(2007)reportedresultsforstarch-based lmsthatarequalitativelysimilartoresultsreportedbytheauthorsabove.Forhighrelativehumidityrange,thevaluesincreased6-foldfor lmswithglyceroland7-fold …… 此处隐藏：22732字，全部文档内容请下载后查看。喜欢就下载吧 ……