Mechanical extraction of oil from Jatropha curcas L. kernel

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ContentslistsavailableatScienceDirect

Industrial Crops and Products

j ou rn a l h o m epa g e :w w w . e l s e v i e r . c o m / l o c a t e / i n d c r o p

Mechanical extraction of oil from Jatropha curcas L. kernel: Effect of processing parameters

Erna Subroto

^a

, Robert Manurung

^b

, Hero Jan Heeres

^a

, Antonius Augustinus Broekhuis

^a,∗

aDepartmentofChemicalEngineering,RijksuniversiteitGroningen,Nijenborgh4,9747AGGroningen,TheNetherlands

bSchoolofLifeSciencesandTechnology,InstitutTeknologiBandung,Jl.Ganesha10,Bandung,Indonesia

a r t i c l e i n f o

Articlehistory:

Received4February2014

Receivedinrevisedform4June2014 Accepted5June2014

Availableonline3July2014

Keywords:

JatrophacurcasL.

Oilseedextraction Hydraulicpress Oilrecovery Oilquality Processparameters

a b s t r a c t

MechanicalextractionisconsideredtobethebestoptionforoilexpressionofJatrophacurcasinruralareas.

Labscalehydraulicpressingexperimentswereconductedtoinvestigatetheeffectofprocessparameters onoilrecoveryfromJatrophakernel.Therangesofpressingparametersinvestigatedwere:compressionspeed,0.05–2.5MPa/s;appliedpressure,5–25MPa;moisturecontent,1–6%;pressingtemperature, 25–105^◦C;pressingtime,1–30min;shellremoval,0–100%;preheatingtime,0–30min;andparticlesize, ﬁne,coarseandwholekernel.Chemicalanalysessuchasacidvalue,phosphoruscontent,oxidativesta- bilityindexandwatercontentwerecarriedouttodeterminethequalityoftheoil.Moisturecontentwas foundtoinﬂuenceoilrecoveryatanyappliedpressureandpressurerates.Oilrecoveryincreasedtosome extentwithanincreaseintemperatureorpressingtime.Thepreferredmoisturecontentwasfoundto beabout4%(w.b.).ThepresenceofJatrophashellandsizereductionofthekernelreduceoilrecovery.

TheoptimumoilrecoverywithrespecttotimeofpressingandoilqualitywasobtainedwhenJatropha kernelwaspressedat15MPa,90^◦C,4%(w.b.)moisturecontentfor10minofpressing.Theoilrecovery obtainedattheseprocessingconditionswas86.1%.

1. Introduction

Peoplelivingintheruralareasofdevelopingregionsoftenlack access toenergy sources. Anapproach to provide therequired energyistoenablethegenerationofenergyfromlocalresources.

Oneof themostpromising renewable and independentenergy sourcesinruralareasisJatrophaoil(Francisetal.,2005;Kumar andSharma,2008;MakkarandBecker,2009).Asitisanon-edible oil,itwillnotimpairfoodsecurityissues(Pinzietal.,2009),and, asitcangrowwellonmarginalnon-agriculturalland,itwillnot competewiththelandneededforfoodproductionnorwithnature conservation(MakkarandBecker,2009;Pinzietal.,2009;Achten etal.,2007).Jatrophaisconsideredamoresustainablefeedstockfor energyproductionthananyotherfood-basedcropsuchaspalm, rapeseed,soybeanandsunﬂower(Pinzietal.,2009;Achtenetal., 2007).

DifferenttechniqueshavebeenusedtoextractoilfromJatropha curcasseedorkernel,themostnotablebeingmechanicalpressing,

∗ Correspondingauthorat:DepartmentofChemicalEngineering,Universityof Groningen,Nijenborgh4,9747AGGroningen,TheNetherlands.

Tel.:+31503634918;fax:+31503634479.

E-mailaddress:[email protected](A.A.Broekhuis).

solventextraction(Sayyaretal.,2009),enzymeassistedextraction (Winkleretal.,1997),andmorerecently,supercriticalﬂuidextrac- tion(Chenetal.,2012).Mechanicalpressingisconsideredasthe preferredmethodtoextractoilfromseedespeciallyintherural areasofadevelopingregions(Achtenetal.,2007).Theothermeth- odsprovidetoomuchcomplexityforapplicationinruralareas.

Previousresearchonotherplantoilseedshasshownthatboth seedpretreatmentandpressing parametersinﬂuenceoilrecov- ery(Mpagalileand Clarke,2005;Willemsetal.,2008;).Applied pressure,pressingtemperature,andpressingtimeareimportant processparameters,whiletheadjustmentofseedmoisturecontent isshowntobethemostimportantfactoramongstpretreatments suchasremovalofhullsorshells,sizereductionorheattreatment (Willemsetal.,2008).Theeffectofmoisturecontentonoilrecovery alsoappearstoberelatedtothetypeoffeedstock,aseachoilseed seemstohaveaspeciﬁcoptimummoisturecontent(Mpagalileand Clarke,2005;Achehebetal.,2012).

Acidvalue,phosphoruscontentandoxidativestabilityarethe propertiesusedtodeterminethequalityoftheoilexpressed.Each ofthesecanberelatedtopretreatmentconditionsortothepress- ingoperationwhichleadstothegeneralconclusionthatdeleterious effectssuchaslongprocessingtimes,contactwithoxygen,expo- suretohightemperatures,lightandcatalystsshouldbeavoided (Nawar,1996).Willemsetal.(2008)reportedoilyieldsforJatropha http://dx.doi.org/10.1016/j.indcrop.2014.06.018

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Table1

PropertiesofJatrophasamplebeforemoistureconditioning.

Properties JatrophaKalimantan JatrophaCapeVerde Weightfraction,%d.b.

Seed 100 100

Kernel 63.6 62.9

Shell 36.4 37.1

Oilcontent,%d.b.

Seed 37.1 36.5

Kernel 58.3 58.0

Shell 0.0 0.0

Moisturecontent,%d.b.

Seed 8.6 6.9

Kernel 7.0 5.3

Shell 11.3 9.6

seedand kernel pressed at various pressuresand temperature.

While,Tambunanetal.(2012)studiedtheinﬂuenceofcrushing, preheatingtimeandpressingtemperatureonyieldfromJatropha seedandkernel.Bothstudiesreportedahigheroilrecoveryfrom kernelthanfromcompleteseeds.

RemovalofshellandoilextractionfromJatrophakernelisnec- essarybecausetheshellabsorbsoilduringexpressionwhichresults inloweroilrecoverywhenpressingthewholeseed(Willemsetal., 2008).Jatrophashelldoesnotcontainsigniﬁcantamountsofoil (0.5–1.4%d.b.)(Gübitzetal.,1999)andtheseedhashigherhard- nessandenergyfor rupture(50–300N/mm;25–95Nmm)than thekernel(10–40N/mm;7–28Nmm)(KarajandMüller,2010).

Thusexpressionofseedwillrequiredmoreenergyincomparison withkernel.Extractionfromkernelproducesalight-colored,low- ﬁber,andprotein-richcake.Inaddition,thereareseveralpotential applicationsofJatrophaseedshell,forexampleasparticleboard (Weveretal.,2012),activatedcarbon(KumarandNamasivayam, 2009),pyrolysisoil(Manurungetal.,2009),fuelforcombustion units(KratzeisenandMüller,2013)andgasiﬁerfeedstock(Vyas andSingh,2007)whichwilladdsomeeconomicvalue.

Literaturecoveringtheinﬂuenceofpretreatmentandoperating conditionsduringhydraulicpressingofJatrophaoilfromkernelis limited.Thisresearchthereforeisaimedtostudytheinﬂuenceof processparametersonoilrecoveryfromJatrophakernelinmore detail.Compressionspeed,appliedpressure,moisturecontentof sample,pressingtemperature,durationofpressing,feedstocksize reduction,shellremovalandpreheatingtimewerestudiedasvari- ables,andthequalityoftheobtainedoilswasevaluated.

2. Materialsandmethods 2.1. Material

Theexperiment wasconductedusingJ.curcas L.seedsfrom Palangkaraya, Central Kalimantan, Indonesia. The maturefruits wereharvestedmanuallyin March2011.Theseedsweredried undersunandstoredinjutebagsinawarehousefacilityattemper- aturesbetween20and30^◦Candrelativehumidityof80–90%for onemonth.Jatrophashellswereremovedmanuallyandboththe kernelsandshellswereanalyzedforinitialmoistureandtotaloil content.InadditiontoJatrophafromKalimantan,Jatrophafrom CapeVerdewasused foroilquality analysis(see Table1).The harvestingandpostharvestinghistoryfortheJatrophafromCape Verdeisunknown.TheseedswereimportedintotheNetherlands inFebruary2009.AftertransporttotheNetherlands,bothseeds werestored atatemperatureintherangeof15–25^◦Candat a relativehumidityof40–50%.Theseedshellswereremovedman- uallyandthekernelswereexposedtosomepretreatmentsbefore beingpressed(describedbelow).Thepretreatedkernelswereused directlyin thepressing experimentstoreduce theinﬂuence of

Fig.1.PartsofJatropha:(a)seeds,(b)kernels,and(c)shells.

storagetimeandconditiononoilquality.Theoilanalyseswere conducteddirectlyafterpressinginMay2011andSeptember2011 forJatrophaKalimantanandCapeVerde,respectively.

Potassiumhydroxide(pellets,85%,Vetec),oxalicacidanhydrous (≥99%,Sigma–Aldrich),ethanol(95%,Sigma–Aldrich),diethylether (≥99%,Sigma–Aldrich)hexane(≥99,Sigma–Aldrich),Hydranalsol- vent (Fluka) and Hydranal titrant 5 (Fluka) were bought from Sigma–Aldrich(Amsterdam,TheNetherlands).

2.1.1. Kernelpretreatments

Jatrophakernelsweregivensomepretreatmentsbeforebeing pressed.Thoseweremoistureconditioning,shellremovaland/or sizereductionforkernel.

2.1.1.1. Shell removal.In theexperiments tostudythe effectof shellremoval,thetotalweightsofsamples(shellsandwholeker- nels)wereapproximately7geach.Themoisturecontentofkernel andshellwere4and8.4%(w.b.),respectively.Atthesemoisture contents,seedcontains62.5%(w.b.)kerneland37.5%(w.b.)shell.

Thestatedpercentageofshellremovalisthepercentageofshell removedfrom theoriginal sample.0% removalmeans thatthe experimentuses100%seedsorcorrespondstoashellcontentof 37.5%(w.b.),while100%removalmeansthattheexperimentuses 100%kernelsorcorrespondswithashellcontentof0%(w.b.).The oilrecoverywascalculatedonthebasisofoilcontentandweight ofkernel(shellcontainsnooil).Experimentswerecarriedoutwith removalof0,20,40,60,80and100%oftheshell.Unlessstatedoth- erwise,thesamplesconsistofwholekernelor100%shellremoval.

2.1.1.2. Moistureconditioning.Forquantitativeanalysis,thewhole kernelswereconditionedbyovendrying.Thedryingtemperature were30,35, 40, 50,60, and70^◦Cfor desiredmoisturecontent of6,5,4,3,2and1%w.b.,respectively.Afterdrying,thekernels werewrappedtightlyinalowdensitypolyethylenebagof25␮m thicknessandthenputinsideadesiccatorcontainingsilicagelfor 24hbeforebeingpressed.Foroilqualityanalysis,thekernelswere equilibratedinsidethedesiccatorcontainingsilicagelorwateruntil theyreachthedesiredmoisturecontentandthenwrappedinthe polyethylenebag.Theinitialmoisturecontentofthesamplewas determinedbyusingthestandardovenmethodat105^◦Cfor24h.

Moisturecontentsafterconditioningweredeterminedbasedon theweightdifferenceofthesampleafterandbeforeconditioning.

Unlessstatedotherwise,wholekernelwithamoisturecontentof 4%(w.b.)wasused.

2.1.2. Sizereduction

Aftermoistureconditioning,thewholekernelsweregrinded into two particle sizes: a ﬁnely ground sample [which passed 2.36mm andwereretainedbya 1.17mmsieve]anda coarsely groundsample[whichpassed4.75mmandretainedbya3.33mm sieve].Unlessstatedotherwise,wholekernelwasused(Fig.1).

2.2. Hydraulicpressing

A speciallydesigned laboratoryhydraulic press wasusedto studytheeffectofprocessingparametersonoilrecoveryfromthe Jatrophasamples.Aschematicrepresentationofthepressisshown

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Fig.2. Schematicrepresentationofthehydraulicpress.

inFig.2.Thepressingchamberismadefromstainlesssteelwitha diameterof20mmandaheight70mm.Itisequippedwithaperfo- ratedplate(diameterholeof1mm)coveredwithstainlesssteel(SS) wiremesh(100mesh)placedatthebottomofthepressingchamber actingasﬁlterduringextraction.Anelectrical-resistanceheating ringbeingattachedaroundthepressingchamberisusedtopreheat thepressingchamberduringoperationwithinatemperaturerange of30–105^◦C.Forexpressionat25^◦C,theheatingringwasremoved.

Pressuresupto25MPawereappliedbyahydraulicplunger.The pressisequippedwithathermocouple(±1^◦C),pressuremeasure- ment(±1MPa),andalevelindicator(±0.01mm),whichmeasures thedistancetheplungertraveled.

Approximately7gofpretreatedsamplewasplacedinthepress- ingchamber.Afterwards,theplungerisputontopofthesample.

Unlessstatedotherwise,thesampleispreheatedatthedesired pressingtemperaturefor5min.Preheatingtimeisthedurationof thesampleatthepressingtemperature,beforeitwaspressedfor actualoilextraction.Thepressureisincreasedlinearlyatthepre- deﬁnedcompressionspeeduntilthedesiredpressureisreached.

Unlessstatedotherwise,thesampleispressedatacompression speedof0.125MPa/s.Totalpressingtimeis10min,exceptforthe experimentsshowingtheinﬂuenceofpressingtime.Threerepli- catemeasurementswereperformedforeachsampleandaverage valuesweretaken.

2.3. Totaloilcontentandoilrecovery

Theoilcontentofthesamplewasdeterminedusingstandard Soxhletextractionmethods.Thekernelsweredriedovernightinan ovenat105^◦Cbeforeanalysis.Thedriedkernelsweregrindedusing acoffeegrinder(Princess242195,Netherlands)andapproximately 10gsamplesweretransferredintoacelluloseextractionthimble.

Thiswasextractedwith100mln-hexaneatitsboilingpointfor 24h.Thesolventwasremovedusingarotaryvacuumevaporator (100mbar40^◦C).Thetotaloilcontentiscalculatedonadrybasisof thesample.Theoilrecoveryisdeﬁnedastheratiooftheamountof oilexpressedtothetotaloilcontainedinthesampleondryweight basis.

2.4. Oilqualityanalysis

Hydraulicpressedoilswhich stillcontainedsomeﬁneparti- cleswerecentrifugedat2000×gfor10min.Theclearoilswere

Table2

Theeffectofcompressionspeedatvariousappliedpressures.^a Compressionspeed(MPa/s) Oilrecovery(%d.b.)

10MPa 15MPa 20MPa

0.05 78.2±1.3 81.4±1.0 81.9±1.2

0.125 75.3±0.6 79.8±1.1 81.2±1.2

2.5 67.2±1.3 71.6±1.4 73.2±1.7

aJatrophakernelwithmoisturecontentof4%(w.b.)pressedat60Cfor10min.

recoveredandusedforoilanalysis.Chemicalanalysesofthesam- pleswerecarriedoutaccordingtothestandardtestmethods:DIN EN14104,DINENISO12937,DINEN14112andDINEN14107 foracidvalue,watercontent,oxidativestabilityandphosphorus content,respectively.AccordingtotheGermanfuelstandardDIN 51605:2010-10forpureplantoil,theacidvalue,phosphoruscontent,andwatercontentshouldnotexceed2mgKOH/goil,3ppm, and750ppmrespectively,andoxidativestabilityshouldbeatleast 6h.Mostofchemicalpropertyanalysisofplantoilsampleswascon- ductedinourlaboratorywiththeexceptionofphosphoruscontent analyseswhichwereconductedbyASG Analytik-ServiceGmBH, Germany.Duplicatemeasurementswereperformedoneachsam- pleandaveragevaluesweretaken.

3. Resultsanddiscussion

3.1. Inﬂuenceprocessingfactorsonoilrecovery

JatrophakernelfromKalimantanusedinthisexperimenthas a58.3%d.b.oilcontentandanoriginalmoisturecontentof6.96%

(w.b.)(seeTable1)Therangesofparametersinvestigatedwere:

applied pressure, 5–25MPa; moisture content, 1–6%; pressing temperature,20–105^◦C;pressing time2–30min;shellremoval, 0–100%;preheatingtime,0–30min;and,particlesize,ﬁne,coarse andwholekernel.

3.1.1. Effectofcompressionspeed(pressingrate)

Industrial expression generally applies a linear pressure increaseduringtheearlyphaseofpressingfollowedbyaperiod ofconstantpressure.ThecompressionspeedforJatrophaextrac- tionisstudiedatthreelevels,namely2.5,0.125and0.05MPa/s.

Thecompressionspeedinthisstudyisdefinedasthespeeduntil reachingthefinalpressure.Thetimeneededtoreachitsfinalpres- sureof10MPaatacompressionspeedof2.5,0.125and0.05MPa/s were4,80and200s,respectively.Increasingthespeedfrom0.05 to2.5MPa/sreducedtheoilrecoveryfrom78.2to67.2%(d.b.)for Jatrophakernelwithamoisturecontentof4%(w.b)(seeTable2).

At higher compressionspeeds, the oilinitially releasedinto theinter-kernelvoidsexperiencesresistancetoflowthroughlow- porositycompressedcakeduetocompactionofthecakeatthe beginning of pressing operation. This reducesthe porosity and restrictstheflowofoil.Increasingpressurescanhelptopushthe oilout.AsshowninTable2,whentheappliedpressureisincreased from 10 to 20MPa at highcompression speeds (2.5MPa/s), an increaseinoilrecoverywasobservedfrom67.2to73.2%(d.b.).Slow deformationlongermaintainstheporosityneededforfreeoilflow untilitreachesthemaximumconsolidationpoint.Bytuningthe compressionspeed,ahighoilrecoveryatlowerappliedpressure canbeachieved.

TheoilrecoveryproﬁlesforpressingJatrophakernelwithmois- turecontentsof4%(w.b.)arerecordedasafunctionofpressing timeatthreedifferentcompressionspeeds(Fig.3).Oil recovery slowlyincreasedandﬁnallyreachedthemaximumvaluewhen Jatrophakernelwasbeingpressed at15MPa withcompression speedof2.5MPa/s.Meanwhile,almost90%ofoil(fromthetotal oilexpressedafter10minofpressing)wasrecoveredafter4minof

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Fig.3. OilrecoveryproﬁlesofJatrophakernelspressedatdifferentcompression speeds(moisturecontentofkernels:4%(w.b.);appliedpressure:15MPa;pressing temperature:60^◦C;10minpressing).

Table3

Theeffectofcompressionspeedatvariousmoisturecontents.^a Compressionspeed(MPa/s) Oilrecovery(%d.b.)

1%(w.b.) 4%(w.b.) 6%(w.b.)

0.05 63.5±1.5 81.4±1.0 71.4±1.2

0.125 64.5±1.3 79.8±1.1 65.1±0.7

2.5 62.9±1.3 71.6±1.4 41.8±1.7

aJatrophakernelpressedatappliedpressureof15MPaat60Cfor10min.

pressingat0.125MPa/s.WhenJatrophakernelisbeingpressedat acompressionspeedof0.05MPa/s,thereisnooilrecoveredduring thefirstminuteofpressing.Theoilrecoveryprofileseemssimilar forthecompressionspeedsof0.125MPa/sand0.05MPa/s,except for0.05MPa/swheretherewas1mindelayduetothelongertime neededtoreachtheoilpointpressure.Oilpointpressureisdefined asthevalueofappliedpressureatwhichoilflowsoutoftheker- nelparticlesortheminimumpressuresneedformechanicaloil expression(Heráketal.,2013;Ajibolaetal.,2002).Thereisnosig- nificantdifferenceinoilrecoveryforpressingJatrophakernelat compressionspeedsof0.125MPa/sand0.05MPa/s.

Theeffectofcompressionspeedwasevaluatedatthreedifferent moisturecontents,namely1,4and6%(w.b.).Atamoisturecontent of6%(w.b.),oilrecoveryreducedfrom71.4to41.8%(d.b.)with increasingthecompressionspeedfrom0.05to2.5MPa/s.Whileat themoisturecontentof4%(w.b),increasingthespeedfrom0.05 to2.5MPa/sreduced theoilrecoveryfrom81.4to71.6%(d.b.).

However,this oilrecoveryreduction didnot happenwhen the driedkernelwaspressed,forexampleat1%(w.b.),theoilrecovery remainedmoreorlessconstantatanon-optimumlevelofaround 63–64%(d.b.)asshowninTable3.Ourdataindeedconﬁrmedwork reportedbyWillemsetal.(2008),whoconcludedthattheeffect ofcompressionspeeddidnotaffectoilrecoverywhenusingrela- tivelydrysamples(moisturecontentof0%w.b.).Yet,theconclusion appearednottobevalidforhighermoisturecontents,asfoundin thisstudy.

Theeffect of moisturecontent ontheoilrecovery couldbe explainedbytheabilityofoilandwatertowetthesurfaceofthe seedparticles.Waterisknowntoactasaninterfacialagentbetween theprotein-richcakeandtheoil,whichformspaste-likeplastized material.Alowercompressionspeedhelpsincontinuousoiland waterremoval fromtheseedand preventsexcessivemixing of

Fig.4.EffectofappliedpressureandmoisturecontentonoilrecoveryofJatropha kernelpressingat60^◦Cfor10min.

thesefractionswiththeprotein-richcake.Highmoisturecontent ofkernelneedsslowerdeformationforoptimumoilexpression.

3.1.2. Effectofmoisturecontentandappliedpressure

The effects of appliedpressure and moisture contenton oil recoveryareshowninFig.4.Acomparativestudyoftheresults showedthattheoilrecoveryatanypressurewasaffectedbythe moisturecontentofthesample.

Theoilrecoveryincreasesfroma low valueat themoisture contents of 1% (w.b.) to reach a maximum value at moisture contentsofbetween4and5%(w.b.)forallappliedpressures.There- aftertheoilrecoverydecreaseswithafurtherincreaseinmoisture contentfor allextractionpressures.For example, atanapplied pressureof15MPa,oilrecoveryincreasesfrom64.5to79.8%(d.b.) withanincreaseinmoisturecontentfrom1to4%(w.b.)andthen decreasedto65.1%(d.b.)withafurtherincreaseofmoisturecon- tentto6%(w.b.).Inaddition,itwasobservedthatatamoisture contentof6%(w.b.),theoilwascontaminatedwithﬁneparticles containingwaterwhichmadetheobtainedoilcloudy.Asreported byKarajandMüller(2010),thepresenceofmoistureinﬂuencesthe hardnessofJatrophakernelwithahigherhardnessatlowermois- turecontent.However,atexcessmoisturelevel,thepresenceof waterwillactsasplasticizerbetweentheprotein-richcakeandoil whichformspaste-likeplastizedmaterial.Itseemsthatoptimum moisturelevelsshifttolowervaluesaspressuresincrease.Atlow pressure,theoptimummoisturecontentis5%(w.b.)whileathigher pressuretheoptimummoisturecontentis4%(w.b.).Thisobserva- tionisinagreementwiththeworkcarriedoutbyMpagalileand Clarke(2005).Inordertogethigherrecoveriesitwouldbeprefer- abletoextractoilatmoisturecontentsofJatrophakernelcloseto 4%(w.b.).Achehebetal.(2012)found3.95%asoptimummoisture contentforpistachionut.

Effectofmoistureonoilrecoveryismorepronouncedatlow pressure.Astheappliedpressureincreases,theeffectofmoisture contentbecomesmorenegligible.Atappliedpressureof5MPa,the oilrecoveryvariedbetween44.0and67.9%(d.b.)forkernelwith moisturecontentof1and5%(w.b.),respectively.Whileat25MPa, theoilrecoveryrangedfrom74.7to81.6%(d.b.)forkernelwith moisturecontentof1and4%(w.b.),respectively.Exceptforpress- inghighmoisturecontentof6%(w.b.),wheretheeffectofpressure isnegligible.Duetothelowpressureused,oilrecoveriesareinﬂu- encedbyhardnessofthekernel,givinghigheroilrecoveryathigher moisture.Asthepressureincreases,maximumcakeconsolidation

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Fig.5.EffectofpressingtemperatureandtimeonoilrecoveryfromJatrophakernel withmoisturecontentof4%(w.b.)pressingat15MPa.

isachievedregardlessofmoisturecontentused.Pressingat25MPa isalmostinsensitivetomoisture(below5%w.b.)whichmakesit idealforcommercialoperationsasthemoisturecontentofthefeed- stockmayvaryoverawiderrangewhilestillahighrecoverycan beachieved.Thisobservationisinagreementwiththeworkcar- riedoutbyMpagalileandClarke(2005)whostudiedtheeffectof moisturecontentonoilrecoveryfromcoconutatvariousapplied pressures.

Generally,there was anincrease in oilrecoveryas pressure increasedfrom5MPato25MPa.Increasingtheappliedpressure leadstotheincrease of oilrecoverywhen Jatrophakernelwas pressedupto3%(w.b.)moisturecontent.Beyondthis moisture content,theoil recoveryincreasesas thepressure increasesto 15MPaandeitherleveledoffordecreasedwhenpressureisraised to25MPa.Areductioninoilrecoverywithapressureincreaseto 25MPawasobservedandtheeffectismorenoticeableinsamples withhighmoisturecontents.Athigherpressure,theemptyvoids betweenparticlesfromwhichtheoilcouldflowwerebecoming smallerandsealed,andthusrestrictedtheflowofoil.Theseresults indicatethatexcessivepressuredoesnotnecessarilyhaveapositive influenceonoilrecovery.

Theoilrecoveryincrementastheresultofpressureincrease variedwithmoisturecontent.Atamoisturecontentof1%(w.b.), increasingpressure from5MPa to25MPa gave anoilrecovery incrementasmuchas30.7%;i.e.from44.0%to74.7%.Meanwhile, atmoisturecontentof6%(w.b.),theoilrecoveryshiftedfrom62.5%

to65.1%aspressureincreasedfrom5to15MPaanddecreasedto 61.8%aspressureincreasedto25MPa.Moistureaffectsthehard- nessandcompactnessofthekernel.Atlowermoisturecontents, moisturelosscausesthesurfaceofthesampletoharden,andit requiresahigherappliedpressuretobreakthehardenedsurface duringpressing. Consequently, theincreasingpressure leadsto theincreaseof theoilrecovery.Meanwhile, athigher moisture contents,thewateractsasainterfacialagentbetweentheprotein- richcakeandoilwhichformspaste-likeplastizedmaterialthus restrictingtheﬂowofoil.Increasingpressureathighermoisture contentincreasedthecompactness ofcake, thusreduce theoil recovery.

3.1.3. Effectofpressingtemperatureandtime

Theeffectofpressingtemperatureandtimeonoilrecoveryis presentedinFig.5.Theeffectoftheseparametersontheoilrecov- erywasstudiedat15MPaandmoisturecontentof4%(w.b.).

Temperature is found to affect the oilrecovery of Jatropha oilwhich is in agreementwith earlier studieson theeffect of temperatureonoilrecoveryfromoilseeds(MpagalileandClarke, 2005;Willemsetal.,2008;Ebeweleetal.,2010).Astemperature increases,oilrecoveryincreasesbuttendstoleveloffathighertem- perature.Forexampleatapressingtimeof10min,oilrecovery increasefrom58.6to87.2%astemperaturerisefrom25to105^◦C.

Itwasobservedthatat105^◦C,thecolorofoilbecamedarkerandthe resultantcakewasdryandhard.Increasingtemperatureraisedoil recoveryduetobreakdownofcellwalls,causedproteindenatur- ationandcoagulation,andreducedoilviscosity,thusfacilitatingthe releaseoftheoilfromthecellsintotheinter-kernelvoids(Willems etal.,2008).However,increasingpressingtemperaturereducedthe oilrecoveryincrement.Thisphenomenoncouldbeattributedto thefactthatwaterevaporatesfasterathighertemperaturecausing substantialmoistureloss;thecompressedcakebecomeshardand drythusreducingtheoilﬂowthroughthecompressedcake.This observationisinagreementwiththeworkcarriedoutbyMpagalile andClarke(2005)andWillemsetal.(2008).

Theinﬂuenceofpressingtimeis showninFig.5.Ingeneral, oilrecoveryincreasedwithincreasingpressingtimeatallpress- ingtemperatures.Oilrecoveryincreasedprogressivelywhenthe pressingtimewasincreasedfrom1minto10min.Uponincreas- ingpressingtimeupto30min,oilrecoverygraduallyleveledoffto aconstantvaluedependingonthepressingtemperatureused.For exampleattemperatureof90^◦C,oilrecoveryincreasedto86.1%

after10minandﬁnallyreached94.1%after30minofpressing.The amountofoilextractedincreasedwithpressingtimewithmore than50%(ofthetotalexpressedoilafter30minofpressing)recov- eredin1minandabout90%after10minofpressing.Itislikely thatanincreaseinthepressingtimeattheappliedpressureled toslowcakedeformationandcompactionofthecake.Thiscaused restrictedﬂowoftheoilfromthecakeandareductionoftheoil expression(MpagalileandClarke,2005).

3.1.4. Effectofshellremoval

Mechanicalseparationofshellfromkernelpotentiallycouldnot achievefullseparation.Therefore,theeffectofshellisinvestigated todeterminewhetheritspresencehasaneffectonoilrecovery.

Acomparativestudyshowedthatanincreasein theamountof shellreducedoilrecovery(seeTable4).Extractionofneatkernel (100%shellremoval)gavea25.6%higheroilrecoverythanextrac- tionofseed(0%shellremoval).However,thehighestoilrecovery is achievedat80% shellremoval. Similarresultswereobtained byWillemsetal.(2008),withoilrecoveriesof33–52%fordried Jatrophaseedsand62–75%fordriedJatrophakernelspressedat 20–70MPa,40^◦Cfor10min.Accordingtothisauthor,Jatrophashell containsnooil;thepresenceofasignificantquantityofshellmay leadtoabsorptionofoilbythefiberintheshell,therebyreducingoil recovery.Inaddition,whenusingseeds,theshellsconsumepartof thepressure,whereasforkernel,allthepressureisusedtoexpress theoil.Thepresenceofsmallquantitiesofshellhelpstomaintain porosityinthesamplethusfacilitatestheflowofoilthroughthe compressedcake.

3.1.5. Effectofparticlesize

Three sizes of samples were used to investigate the effect of size reduction on oil recovery, i.e. whole, coarsely ground (3.33–4.7mm),andfinelygroundkernel(1.17–2.36mm);Table5 summarizestheeffectofsizereductionofJatrophakernel.Theoil recoveriesfromwhole,coarselyandfinelygroundkernelare74.5, 71.8and69.3%(d.b.)at10Mpaand81.3,77.5and75.1%(d.b.)at 20Mpa,respectively.WholeJatrophakernelgaveahigheroilrecov- erythancoarselyandfinelygroundatallappliedpressurelevels.

ConﬂictingresultshavebeenreportedbyTambunanetal.(2012) withasigniﬁcantlyhigheroilrecoveryforcoarsesamplesthanfor

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Table4

Effectofshellremovalonoilrecovery^aminutes.

Shellremoval(%w.b.) K(g) So^b(g) S^c(g) Kernel(%w.b.) Shell(%w.b.) Oilrecovery(%d.b.)

100 7.00 4.20 0 100 0 79.8±1.1

80 6.25 3.75 0.75 89.3 10.7 81.7±1.1

60 5.65 3.39 1.36 80.6 19.4 76.1±0.6

40 5.15 3.09 1.85 73.5 26.5 73.8±1.4

20 4.73 2.84 2.27 67.6 32.4 68.3±1.4

0 4.38 2.63 2.63 62.5 37.5 54.2±0.7

aJatrophasample(moisturecontentofseed:5.6%(w.b.),kernel:4%(w.b.),shell:8.4%(w.b.))pressedat15MPaat60Cfor10min.

b Originallyshellweight(So)=37.5/62.5×kernelweight(K).

c Shellweightafterremoval(S)=(100−%shellremoval)×originallyshellweight/100.

Table5

Effectofparticlesizeonoilrecovery.^a

Appliedpressure(MPa) Oilrecovery(%d.b.)

Whole Coarse Fine

10 75.3±0.6 73.1±1.2 70.6±1.7

20 81.2±1.2 78.9±0.9 76.5±0.4

aJatrophawholekernelwithmoisturecontentof4%(w.b.)pressedatapplied pressureof10and20MPaat60Cfor10min.

Table6

Effectofpreheatingtimeonoilrecovery.^a

Preheatingtime(min) Oilrecovery(%d.b.)

0 77.8±0.6

5 79.8±0.6

15 80.7±0.5

30 81.2±0.8

aJatrophawholekernelwithmoisturecontentof4%(w.b.)pressedatapplied pressureof15at60Cfor10min.

wholeJatrophasamples.ThehigheroilrecoveryforwholeJatropha kernelcomparedtotheothersizescanbeexplainedbythebigger voidsformedbythewholekernelsamplescomparedtothoseof thecoarselyandfinelygroundones.Despitethelargersurfacearea exposedtopressureandheattreatmentandtheincreasednumber ofrupturedcells,whichshouldresultsinahighoilconcentrationat theparticlesurface,thesmallerinter-particlevoidsrestricttheflow ofoilthroughthecompressedcake.Pressingwholekernelprovides abetterporosityinthecakewhichenablesbetteroilflow.

3.1.6. Effectofpreheatingtime

Toevaluatetheeffectofpreheating,Jatrophakernelispreheated insidethepressingchamber.Inthisexperiment,itisobservedthat 5minofpreheatingissufﬁcienttoincreaseoilrecoveryfrom77.8%

to79.8%.Furtherincreasesofthetimeto30mindidnotsignifi- cantlyraisetheoilrecovery(seeTable6).Initialmoisturecontent beforepre-heatingwas4%(w.b.)whilemoisturecontentafterpre- heatingwere3.92,3.80and3.66for5,15and30minpreheating, respectively.Apparently,longerpreheatingatthisconditionhas nosignificantinfluenceonoilrecoveryduetohardeningofthe kernelsurfaceand moistureloss.Thisis inagreementwiththe resultsobtainedbyTambunanetal.(2012)intheirstudyonthe effectofpreheatingtimeonJatrophapressing.Inaddition,longer heatingtimescanreducethemoisturecontentbelowtheoptimum moisturecontentfoundinthisstudyof4%(w.b.).

3.2. Qualityparameters

Someimportant oilquality criteriafor Jatrophaoils arepre- sentedinTable7. Acidvaluereﬂectsthefreefattyacids(FFAs) andotherpossibleorganicacids.FFAsarearesultofthehydrolytic degradationof oilduringstorageor processing, i.e.thehydrol- ysisof ester bondsin lipidsby enzyme action or byheat and

moisture.Theoxidativestabilityindexisassociatedwiththeoxida- tivedegradationofoilwhichresultsinranciditydevelopment.A higheroxidativestability index(OSI) expressedinhoursInduc- tionPeriod(IP)meansthattheoilismoreresistancetooxidation.

Phosphoruscontentindicatesthepresence ofphosphor-derived componentsinoilsuchasphospholipidsandphytates.

Ingeneral,JatrophaoilfromKalimantanhasahigherphospho- ruscontentcomparedtoJatrophaoilsfromCapeVerdeasshownin Table7.Thesoilnutritionorfertilizerisconsideredtobecontribut- ingtothisresult.AccordingtoLickfettetal.(1999),phosphorus contentinseedisaffectedbythelevelofphosphorusfertilizersup- plyorphosphoruscontentinsoil.ItispossiblethatJatrophafrom Kalimantanisplantedonbetternutritiouslandthantheonefrom CapeVerde.

TheacidvaluesofJatrophaoilsfromCapeVerdewerehigher thanthoseforJatrophaoilsfromKalimantan,whiletheoxidative stabilityoftheformerwaslower.Thisisprobablyduetothelonger storagetimeofseed.JatrophaKalimatanisfreshlyharvestedseed, while JatrophafromCapeVerde hasbeenstored at±7%(w.b.) moisturecontent,withinatemperaturerangeof15–25^◦Candat arelativehumidityof45%forminimum2.5years.Accordingto Murthyetal.(2003),thequalityofoildependsonthewaythe seedsaredried, treatedand stored. Storageconditions,suchas moisturecontentofseedduringstorageandtemperaturealsohave beenreportedtocontributetotheﬁnaloilquality.Worangetal.

(2008)reportedtheacidvalueincreasedfrom0.1to1.1mgKOH/g oilafterJatrophaseed isstored at8%moisturecontent,atem- peratureof26 ^◦C,and arelativehumidityof70%for6months.

Otherstudiesshowedsimilarresults,withhydrolyticandoxidative degradationrelatedtotimeofstorageandstorageconditions(Bax etal.,2004;Wagneretal.,2003).Factorssuchasinitialmoisture content,storagetemperatureand/orhumidityincreasetherateof seeddeterioration.

Increasing moisture content of kernel from 2 to 6% (w.b.) increasesthePhosphoruscontentfrom1.4to3ppmandacidvalue from1.03to1.19(seeTable7,sectionB).AccordingtoPrioretal.

(1991a)thephospholipidcontentintheoilisreducedbyadecrease inseedmoisture.Seedswith5%and9–11%moisturecontained, respectively,twoandthreetimesasmuchphospholipidthanseed with2.5%moisturecontent.Asa resultofthisriseinphospho- ruscontent,theoxidativestabilityisalsoincreasing;phospholipids andphytatesareknownasnaturalantioxidant(Prioretal.,1991b;

ChoeandMin,2006).Holser(2003)studiedtheeffectofmoisture andtemperatureontheoilqualityofconditionedmeadowfoam (Limnanthesalba).Itisreportedthatmoisturehasastrongereffect thantemperatureontheincrease inFFAcontent(acidvalue).A highermoisturecontentoftheseedswouldenablehydrolysisof triglycerides.

Increasing pressing temperaturesraises the acidvalues and phosphorus contents of the oil. Acid value increased with an increase in pressing temperature from 25 to 60^◦C. However a slightly reduced acid value was observed when pressing tem- peratureincreasedto90^◦C.Increasingtemperatureisalsolikely

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Table7

Jatrophaoilqualityatdifferentprocessingconditionsandvarieties.

No Processingconditions Oilquality

AV(mgKOH/goil) Pcontent(ppm) OSI(h) Water(ppm)

(A)JatrophaKalimantan

1 Wholekernel,4%w.b.,10MPa,25^◦C,10min 0.21 15.8 12.70 672

(B)JatrophaCapeVerde

2 Wholekernel,6%w.b.,15MPa,60^◦C,10min 1.19 3 13.07 885

9 Finekernel,4%w.b.,15MPa,90^◦C,10min 1.16 6.8 13.44 838

topromotehydrolysis asreactionratesincrease athighertem- peratures,however,atthehighertemperaturesthiseffectwould bemoderatedbyenzymedegradation.AccordingtoAbigoretal.

(2002),lipaseisolatedfromJatrophaseedshowsthehighestactiv- ityatatemperatureof37^◦C.Thedisruptionofcellstructureand solubilizationofphospholipidsoccurredathighertemperatures.

Althoughphosphorusispresentatahigherlevelwhentheoilis pressedathighertemperature,theoxidativestabilityoftheoilis lower.Highpressingtemperatureincreasestherateofautoxidation andconsequentlyitconsumestheavailablenaturalantioxidants includingphospholipids.Thisresultisinaccordancewiththedata reportedbyTambunanetal.(2012),showingthatprolongedheat treatmentatahightemperaturereducestheoil’soxidativestability andincreasesoilacidity.

FinelygroundJatrophakernelhasahigheracidvalueandphos- phorus content than whole kernel. Adeeko and Ajibola (1990) mentionedthatparticlesizehasasigniﬁcanteffectonacidvalueof oilwiththeﬁnelygroundnutshavingahighervalue.Theformation ofFFAinseedsstartswiththedestructionofcells.However,acid formationislimitedtothedestroyedcellsduringsizereduction.

Ahighernumberofcellsdestroyedintheﬁnelygroundsamples thusaccountsforthehigheracidvalueandphosphoruscontent.

Sizereductionincreasesexposedareatoheat,moistureandoxygen.

Sizereductionalsogaveahigheroxidativestability,possiblydueto theco-extractionofothernaturalantioxidants,suchastocopherol.

Highheatingtemperatures,longheatingtimesandsizereduction resultedinhigheracidvalueandphosphoruscontent.

Thepresenceofwatercanpromotethehydrolysisreactionand thegrowthofmicro-organismsduringstorageofoil.Watercontent canincreaseduringstorageduetowaterabsorptionfromair;thus properpackagingisneededtoavoidwaterabsorption(Heandvan Gerpen,2012).Amaximumwatercontentof750ppmisrequired byGermanStandardDINV51605.

4. Conclusions

Fromtheparametersstudiedinthisworkthefollowingcanbe concluded:foroilexpressionfromkernelswithahighmoisture contentaslowercompressionspeedispreferred.Pressure,tem- peratureandpressingtimeallhavepositiveeffectsonoilrecovery, butnegativeeffectonoilquality.Kernelsizereductionhasaneg- ativeeffectonoilrecoveryandquality.Moisturecontentinthe rangeof4–5%(w.b.)gavethehighestoilrecovery.Aminimumof 80%shellremovalshouldbeachievedtoavoidthenegativeeffectof shellpresenceonoilrecovery.Fiveminutesofpreheatingtimewas foundtobeoptimuminincreasingtheoilrecovery.Jatrophakernel

waspressedat15MPa,90^◦Cpressingtemperature,4%(w.b.)mois- turecontentfor10minofpressinggaveanoilrecoveryof86.1%and goodoilquality.Furtheroptimizationwithinthepressurerangeof 10–20MPa,60–90^◦Candmoisturecontent3–5%(w.b.)isexpected todelivertheoptimumoilrecovery.Thisworkwillbepresentedin separatedpaper.

Conﬂictofinterest

Theauthorshavedeclarednoconﬂictofinterestonﬁnancial and/orcommercialapplicationofthisstudy.

Acknowledgements

The authorsgratefully acknowledgeto theKoninklijkeNed- erlandse Akademie van Wetenschappen, Scientiﬁc Programme Indonesia–Netherlands (SPIN-KNAW),TheNetherlandsfor the ﬁnancialsupport.WealsowouldliketoacknowledgeAnnaApel- doornandJanvanderVeldefortechnicalandanalyticalsupport.

Finally,theauthorsthank RiaAbdilla,Yusuf Abduhandall col- leaguesattheUniversityofGroningen,DepartmentofChemical Engineering,forallsupportandvaluablesuggestions.

References

Abigor,R.D.,Uadia,P.O.,Foglia,T.A.,Haas,M.J.,Scott,K.,Savary,B.J.,2002.Partial puriﬁcationandpropertiesoflipasefromgerminatingseedsofJatrophacurcas L.J.Am.OilChem.Soc.79,1123–1126.

Acheheb,H.,Aliouane,R.,Ferradji,A.,2012.Optimizationofoilextractionfrom PistaciaatlanticaDesf.seedsusinghydraulicpress.AsianJ.Agric.Res.6,73–82.

Achten,W.M.J.,Mathijs,E.,Verchot,L.,Singh,V.P.,Aerts,R.,Muys,B.,2007.Jatropha biodieselfuelingsustainability?BiofuelsBioprod.Bioreﬁning1,283–291.

Adeeko,K.A.,Ajibola,O.O.,1990.Processingfactorsaffectingyieldandqualityof mechanicallyexpressedgroundnutoil.J.Agric.Eng.Res.45,31–43.

Ajibola,O.O.,Okunade,D.A.,Owolarafe,O.K.,2002.Oilpointpressureofsoybean.J.

FoodProcessEng.25,407–416.

Bax,M.M.,Gely,M.C.,Santalla,E.M.,2004.Predictionofcrudesunﬂoweroildeterio- rationafterseeddryingandstorageprocesses.J.Am.OilChem.Soc.81,511–515.

Chen,C.R.,Cheng,Y.J.,Ching,Y.C.,Hsiang,D.,Chang,C.M.J.,2012.Greenproductionof energeticJatrophaoilfromde-shelledJatrophacurcasL.seedsusingsupercritical carbondioxideextraction.J.Supercrit.Fluids66,137–143.

Choe,E.,Min,D.B.,2006.Mechanismsandfactorsforedibleoiloxidation.Compr.

Rev.FoodSci.FoodSafety5,169–186.

Ebewele,R.O.,Iyayi,A.F.,Hymore,F.K.,2010.Considerationsoftheextractionprocess andpotentialtechnicalapplicationsofNigerianrubberseedoil.Int.J.Phys.Sci.

5,826–831.

Francis,G.,Edinger,R.,Becker,K.,2005.Aconceptforsimultaneouswasteland reclamation,fuelproduction,andsocioeconomicdevelopmentIndiacase.Nat.

Resour.Forum29,12–24.

Gübitz,G.M.,Mittelbach,M.,Trabi,M.,1999.Exploitationofthetropicaloilseed plantJatrophacurcasL.Bioresour.Technol.67,73–82.

(8)

He,B.B.,vanGerpen,J.H.,2012.Analyzingbiodieselforcontaminantsandmoisture retention.Biofuels3,351–360.

Herák,D.,Kabutey,A.,Hrabe,P.,2013.OilpointdeterminationofJatrophacurcasL.

bulkseedsundercompressionloading.Biosyst.Eng.116,470–477.

Holser,R.A.,2003.Seedconditioningandmeadowfoampressoilquality.Ind.Crops Prod.17,23–26.

Karaj,S.,Müller,J.,2010.Determinationofphysical,mechanicalandchemicalprop- ertiesofseedsandkernelsofJatrophacurcasL.Ind.CropsProd.32,129–138.

Kratzeisen,M.,Müller,J.,2013.SuitabilityofJatrophaseedshellsasfuelforsmall- scalecombustionunits.Renew.Energy51,46–52.

Kumar,R.,Namasivayam,2009.Developmentandcharacteristicofactivatedcar- bonsfromJatrophahusk,anagroindustrialsolidwaste,bychemicalactivation methods.J.Environ.Eng.Manage.19,173–178.

Kumar,A.,Sharma,S.,2008.Anevaluationofmultipurposeoilseedcropforindus- trialusesJatrophacurcasL.:areview.Ind.CropsProd.28,1–10.

Lickfett,T.,Matthaus,B.,Velasco,L.,Millers,C.,1999.Seedyield,oilandphytate concentrationintheseedsoftwooilseedrapecultivarsasaffectedbydifferent phosphorussupply.Eur.J.Agron.11,293–299.

Makkar,H.P.S.,Becker,K.,2009.Jatrophacurcas,apromisingcropforthegeneration ofbiodieselandvalue-addedcoproducts.Eur.J.LipidSci.Technol.111,773–787.

Manurung,R.,Wever,D.A.Z.,Wildschut,J.,Heeres,H.J.,2009.ValorisationofJatropha curcasL.plantparts:nutshell.FoodBioprod.Process.87,187–196.

Mpagalile,J.J.,Clarke,B.,2005.Effectofprocessingparametersoncoconutoilexpres- sionefﬁciencies.Int.J.FoodSci.Nutr.56,125–132.

Murthy,U.M.N.,Kumar,P.P.,Sun,W.Q.,2003.Mechanismsofseedageingunderdif- ferentstorageconditionsforVignaradiata(L.)Wilczek:lipidperoxidation,sugar hydrolysis,Maillardreactionsandtheirrelationshiptoglassstatetransition.J.

Exp.Bot.54,1057–1067.

Nawar,W.W.,1996.Lipids.In:Fennema,O.R.(Ed.),FoodChemistry.MarcelDekker Inc.,NewYork,pp.255–287.

Pinzi,S.,Garcia,I.L.,Lopez-Gimenez,F.J.,LuquedeCastro,M.D.,Dorado,G.,Dorado, M.P.,2009.Theidealvegetableoil-basedbiodieselcomposition:areviewof social,economicalandtechnicalimplications.EnergyFuels23,2325–2341.

Prior,E.M.,Vadke,V.S.,Sosulski,F.W.,1991a.Effectofheattreatmentsoncanola pressoils.I.Non-triglyceridecomponents.J.Am.OilChem.Soc.68,401–406.

Prior,E.M.,Vadke,V.S.,Sosulski,F.W.,1991b.Effectofheattreatmentsoncanola pressoils.II.Oxidativestability.J.Am.OilChem.Soc.68,407–411.

Sayyar,S.,Abidin,Z.Z.,Yunus,R.,Muhammad,A.,2009.ExtractionofoilfromJat- rophaseeds-optimizationandkinetics.Am.J.Appl.Sci.6,1390–1395.

Tambunan,A.H.,Situmorang,J.P.,Silip,J.J.,Joelianingsih,A.,Araki,T.,2012.Yieldand physicochemicalpropertiesofmechanicallyextractedcrudeJatrophacurcasL.

oil.BiomassBioenergy43,12–17.

Vyas,D.K.,Singh,R.N.,2007.FeasibilitystudyofJatrophaseedhuskasanopencore gasiﬁerfeedstock.Renew.Energy32,512–517.

Wagner,K.H.,Isnardy,B.,Elmadfa,I.,2003.Effectsofseeddamageontheoxidative stabilityofpoppyseedoil.Eur.J.LipidSci.Technol.105,219–224.

Wever,D.A.Z.,Heeres,H.J.,Broekhuis,A.A.,2012.CharacterizationofPhysicnut (JatrophacurcasL.)shells.BiomassBioenergy37,177–187.

Winkler,E.,Foidl,N.,Gubitz,G.M.,Staubmann,R.,Steiner,W.,1997. Enzyme- supportedoilextractionfromJatrophacurcasseeds.Appl.Biochem.Biotechnol.

63–65,449–456.

Willems,P.,Kuipers,N.J.M.,deHaan,A.B.,2008.Hydraulicpressingofoilseeds:

experimentaldeterminationandmodelingofyieldandpressingrates.J.Food Eng.89,8–16.

Worang,R.L.,Dharmaputra,O.S.,Syarief,R.,2008.Thequalityofphysicnut(Jatropha curcasL.)seedspackedinplasticmaterialduringstorage.Biotropia15,25–36.