ContentslistsavailableatScienceDirect
Industrial
Crops
and
Products
j ourna l h o m e pa 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
Storage
stability
of
Jatropha
curcas
L.
oil
naturally
rich
in
gamma-tocopherol
Joana
Rodrigues
a,
Isabel
Miranda
b,
Leonnardo
Furquim
a,
Jorge
Gominho
b,
Manuel
Vasconcelos
c,
Gonc¸
alo
Barradas
c,
Helena
Pereira
b,
Fernando
Bianchi-de-Aguiar
c,
Suzana
Ferreira-Dias
a,∗aInstitutoSuperiordeAgronomia,CEER,BiosystemsEngineering,UniversityofLisbon,TapadadaAjuda,1349-017Lisbon,Portugal bInstitutoSuperiordeAgronomia,CEF,CentrodeEstudosFlorestais,UniversityofLisbon,TapadadaAjuda,1349-017Lisbon,Portugal cGALPEnergia,UnidadedeBiocombustíveis,RuaTomásdaFonseca–EdifícioGALP–TorreC,1600-209Lisbon,Portugal
a
r
t
i
c
l
e
i
n
f
o
Articlehistory: Received1August2014
Receivedinrevisedform17October2014 Accepted24October2014
Availableonline14November2014
Keywords: Gamma-tocopherol JatrophacurcasL. Oil Seeds Stability
a
b
s
t
r
a
c
t
JatrophacurcasL.isaninterestingtropicaloilcropforbiodieselproduction.However,seedconservation untiloilextractionmaybeaproblemunderhightemperatureandhumidity.Inthisstudy,Jatrophacurcas L.seedsgrowninMozambiqueandpresenting160mg/kgofgamma-tocopherolintheiroilwerestored for42days,indark,at35◦Cand75%or92%relativehumidity(RH).Alongstorage,theoilwasextracted andanalysedintermsoffattyacidcomposition,tocopherolcontent,acidity,initialandfinaloxidation products(monitoredbyK232andK270values,respectively).
Jatrophaseedspresentedaninitialwatercontentof8.4%andanoilcontentof45.7%(drybasis).The oilwasrichinoleic(41.2%)andlinoleic(38.8%)acids.
Along42daysofstorage,theacidityincreasedfrom0.8%to7.4%and25.3%andK270increasedfrom 0.07to0.25and0.46inoilsfromseedsstoredat75%and92%RH,respectively.Simultaneously,adecrease ingamma-tocopherolcontentwasobserved,whichwasmorepronouncedat92%RHthanat75%RH(96% decreaseversus57%decrease).Gamma-tocopherolshowedtoprotecttheoilagainstoxidationprincipally duringthesecondstageofoxidation.Duringthestorageat35◦C,thefattyacidcompositionoftheoils fromseedskepteitherat75%or92%ofhumidity,didnotsignificantlyvarythroughoutthetest.
©2014ElsevierB.V.Allrightsreserved.
1. Introduction
Biofuelsareanalternativetofossilfuelssincetheyoffer numer-ousadvantagesfortheenvironmentnamelyreducedemissionsof greenhousegasesandparticles,aswellasforeconomyand devel-opmentviaenergysecurityandstimulationofruraldevelopment (Smeetsetal.,2007;AETSConsortium,2013).
Asotherdevelopingcountries,Mozambiquehasbeen explor-ingthepotentialforrenewableenergytofulfilitsenergydemands (FAO, 2008). A considerable percentage of Mozambican GDP is spent on fuel and energy, which explains the government’s concern in investigating alternative energy sources, including biofuels (World Bank, 2008; Schut et al., 2010). During the lastdecade,theMozambicangovernmentstimulatedfarmersto growJatropha curcas L. on fallow and marginal soils with the
∗ Correspondingauthor.Tel.:+351213653540;fax:+351213653200. E-mailaddress:suzanafdias@mail.telepac.pt(S.Ferreira-Dias).
aim that Mozambique could become an oil exporting country (Schut et al.,2010).Ever since,investment intheagrofuel sec-torincreasedandexpanded,withseveralmultinationalcompanies demonstrating interest in agro-industrial business centred on Jatropha.
J.curcas L.is a drought-resistant shrubor treebelongingto thegenusEuphorbiaceae,whichiscultivatedinCentralandSouth America, South-EastAsia,Indiaand Africa(Giibitzet al.,1999). It grows in semi-arid marginal sites and can be used for ero-sioncontrol(Heller,1996).TheseedkernelofJ.curcasL.contains 43–59%oilwhich in themajorityof genotypescannot beused forediblepurposeswithoutdetoxification,makingitattractivefor biodieselproduction (MtinchandKiefer,1986; Liberalinoetal., 1988;Sharmaetal.,1997;Winketal.,1997;KumarandSharma, 2008;Rodriguesetal.,2013).Infact,someediblevarietiesofJ. cur-cashavebeencultivatedforhumanfoodfromancienttimesinthe mountainsoftheTotonacapan (Mexico),butduetothe“biofuel program”,thesenon-toxicgenotypesareinseriousriskofbeing lost(Kingetal.,2009;Vera-Castilloetal.,2014).
http://dx.doi.org/10.1016/j.indcrop.2014.10.048
Thestorage of largevolumesof Jatrophaseedsor oilunder tropicalclimateconditionswithoutlossofqualityisnotaneasy task. Inorder tomaintainstability of Jatrophaoil, a good stor-age method needs to be developed. The degradative reactions takingplace in vegetableoils are mainlyhydrolysis and oxida-tion. Oil oxidation occurs in the presence of catalysts such as light, heat, enzymes, metals and metalloproteins. Autoxidation isthemost commonprocesspromotingoxidative deterioration andisdefinedasthereactionofatmosphericoxygenwithlipids, whichis fasterathigher temperatures.It occursviaa free rad-ical chain reaction. Lipid hydroperoxides have been identified asprimaryproductsofautoxidation(ShahidiandZhong,2005). In thepresence of metals or at hightemperatures, these com-pounds are splitin alkoxyradicals to formaldehydes, ketones, acids,esters,alcohols,andshort-chainhydrocarbons,which origi-nateunpleasantodours,characteristicofrancidfats(ChoeandMin, 2006).
Thepresenceofnaturalantioxidantsinvegetableoils,suchas tocopherols,maydelaythebeginningormayslowtherateoflipid oxidationreaction,eitherbyquenchingfreeradicalreactionsor byscavengingoxygen.Tocopherolsareprimaryor chain break-ingantioxidants,which inhibitorslowdownlipidoxidationby interfering either with chain propagationor withinitiation by donatinghydrogenatoms tolipid peroxylradicals.Tocopherols havetwo principaloxidation mechanisms:(i)theymaybe oxi-disedin aoneelectron-transferreactiontoatocopheryl-radical or(ii)theymayreactwithsingletoxygentoforma hydroperox-ide(Neelyetal.,1988;Krieger-LiszkayandTrebst,2006).These reactionscanbereversed,sinceboththetocopheryl-radicaland thehydroperoxidecanbere-reducedtotocopherolbyascorbate. However,undermildacidicconditions,thehydroperoxideissplit totocopherylquinonewhichis anirreversiblereaction( Krieger-LiszkayandTrebst,2006).Tocopherolsarepowerfulantioxidants sincetheyproducestableantioxidantradicalsandhavethe capac-itytocompetewiththelipidsubstrateforoxygen(VanAardtetal., 2004).
Severalexperimentalworkshavedemonstratedthatoil resis-tance towardsoxidation is a functionof its tocopherolcontent (Emanuel and Lyaskovskaya, 1967; Reintonand Rogstad, 1981; JungandMin,1990;Fusteretal.,1998;Kamal-Eldin,2006).Ina previousstudyperformedbyourgroup(Rodriguesetal.,2013), J.curcasL.oilsamplesfrom12accessionsandgrownunderthe sameedaphoclimatic conditions in Mozambiquewere analysed withrespecttotheiroilcontent,fatty-acidcompositionandsterol andtocopherol composition.Inallthesesamples,only gamma-tocopherol,whichisapowerfulnaturalantioxidant(Kamal-Eldin and Appelqvist, 1996), was detected in contents ranging from 68.3mg/kgto181.8mg/kg.
Storagestabilitytestswerealsoperformedwithseedsfromthe accessionpresentinmostoftheplantationarea,withanaverage contentof89mgofgamma-tocopherolperkgofoil.Thesestudies werecarriedoutundertropicalclimateconditions(28◦Cand35◦C, atrelativehumiditiesof75%and92%)for45days.Theoxidation rateoftheoilintheseedsincreasedwithhighrelativehumidity andtemperature(Rodriguesetal.,2013).Ahigherresistanceto oxidationwouldbeexpectedinoilswithhighergamma-tocopherol content.
The aim of this study was to investigate if Jatropha seed oil, from the accession containing the highest amounts of gamma-tocopherol, presents a higher oxidative resistance dur-ing storage, under tropical conditions, than the oilwith lower content of gamma-tocopherol (89.1mg/kg) used in the previ-ousstudies(Rodrigueset al.,2013).Thus, along 42daystorage of seeds, the oilwas extracted and analysed in terms of fatty acidcomposition,tocopherolcomposition,acidityandoxidation products.
2. Materialsandmethods 2.1. Seedmaterial
J. curcas L. plants were planted in December 2010, in Búzi (19◦56S;34◦24E),Sofalaprovince,incentralMozambique, char-acterisedbya“Tropicalrainyclimate–Aw”(KöppenandGeiger, 1939).Theseedsusedin this studywerecollectedfromplants includedinan internationalbreedingand cultivardevelopment programme carried out by N.V. Quinvita (Ghent,Belgium).The seedswerecollectedmanuallyfromhealthyandripenedfruitsthat wereharvestedfromJanuarytoJuly2013(Rodriguesetal.,2013). Afterharvesting,theseedsweremanuallydehulled,airdrieduntil aseedwatercontentbelow10%,andstoredinperforatedplastic bags,accordingtoQuinvita’sprocedureguide.
2.2. Seedstoragestabilitytests
Storagestudieswerecarriedoutunderthehighestaverage tem-peratureobservedattheplantationfieldinBúzi(Rodriguesetal., 2013).Thus,intactseedswerestoredat35◦C,at75%or92% rela-tivehumidity(RH)values,inthedark.Thesemoisturevalueswere achievedbycontactingtheseeds,suspendedinaplasticnet,with thevapourphase ofsaturatedsalt solutionsof sodiumchloride (NaCl;RH=75.1%,T=35◦C)orpotassiumnitrate(KNO3;RH=92.3%,
T=35◦C)inclosedglassvessels(Greenspan,1977).Onealiquotof seeds(ca.65g)storedateachtemperatureandhumiditywas col-lectedevery7days,along42daysandtheoilwasextractedand analysed(cf.Sections2.3and2.4).
2.3. Seedoilextraction
Theseedsamplescollectedalongthestorageexperimentswere crushedwithahammer.Theoilcontainedinthefractionwith par-ticleslowerthan 2mmwasextractedinaSoxtecapparatusfor 4h,usingpetroleumetherp.a.(boilingpoint40–60◦C)as extrac-tionsolvent,aspreviouslydescribed(Rodriguesetal.,2013).The extractedseedoilwasstoredinamberglassflasks,at−18◦C,for
subsequentanalysis.
2.4. Chemicalanalysisofseedoil 2.4.1. Acidity
Theacidity(%offreefattyacids,FFA)ofseedoilwasdetermined accordingtoISOstandard660:2009.TheFFAcontentwasassayed bytitrationwitha0.1Nsodiumhydroxideaqueoussolutionusing phenolphthaleinasindicator.Themasspercentagewascalculated onthebasisofthemolecularweightofoleicacid(282.5).Foreach oilsample,theanalysiswascarriedoutatleastintriplicate. 2.4.2. Oxidationcompounds
OilthermoxidationwasindirectlyevaluatedbyUVabsorbance at232nm(K232)andat270nm(K270)of1%(w/v)oilsolutionin isooctane.
2.4.3. Fattyacidcomposition
The analyses of fatty acid profile of Jatropha seed oil were performedaccordingtotheofficialmethodoftheEuropean Com-munity Regulation (1991), as fatty acid methyl esters (FAME) usinga PerkinElmerAutosystem9000gaschromatograph(GC), equippedwithaFIDandafusedsilicacapillarycolumnSPTM-2380 (60m×0.25mm×0.2mfilmthickness),aspreviouslydescribed (Rodriguesetal.,2013).Theresultswereexpressedasarea per-centageofeachpeakrelativetothetotalarea.
Fig.1.Variationoffreefattyacidcontent(%)ofJatrophacurcasL.oilfromseeds storedat35◦Cunderdifferentrelativehumidity(RH=92%andRH=75%)during42 days.
2.4.4. Gamma-tocopheroloilcontent
Tocopherol composition was performed according to ISO 9936:2006,usinga PerkinElmerHPLCsystemequippedwitha PerkinElmerUV/VISLC295 detector,a PerkinElmerSeries200 PumpandaPeltierColumnOvenPerkinElmerSeries200.The col-umnusedwasaLiChroCART®250-4,LiChrospher®,Si60(5m),as
previouslydescribed(Rodriguesetal.,2013). 2.5. Statisticalanalysis
Foreachdataset,one-wayanalysisofvariance(ANOVA)was performed using the programme Statistica, version 6, Statsoft, Tulsa,OK,USA.PosthoccomparisonswerecarriedoutusingFisher LSDtestatapvalueof0.05.
3. Resultsanddiscussion 3.1. Oilacidity
Jatrophaseedsusedinthisstudypresentedaninitialwater con-tentof8.4%andanoilcontentof45.7%(drybasis).Theoilwasrich inoleic(41.2%)andlinoleic(38.8%)acids(Tables1and2),contained 160mg/kgofgamma-tocopherol,andhadanacidityof0.8%,aK232 of1.1andaK270of0.07.
Alongtheexperiments,thequalityofJatrophaoilswas evalu-atedintermsoftheiracidityandcontentofoxidationproducts. Whentheoilistobeusedforbiodieselproduction,itisimportant thatitdoesnothaveahighcontentofoxidationproductsandfree fattyacids,whichinhibitthechemicalalkalinecatalysts.
Fig.1showstheevolutionofacidityinoilsextractedfromseeds storedat35◦Cand75%or92%RH,along42days.Alinearincrease ofacidityoftheoils(by0.17%FFA/day)extractedfromseedsstored at75%RHwasobservedalongthestorage.Fortheoilsfromseeds storedat92%RH,theacidityalsoincreasedlinearlyduringthefirst 28daysofstorage,atarateof0.23%FFA/dayandfrom28to42days ofstorage,aboutasix-foldincreaseinthehydrolysisrate(1.32% FFA/day)wasobserved.Thismaybeduetothepresenceofhigher amountsofwateravailableforthehydrolysisreactionat92%RH. Inpresenceofhighhumidity,after28daysofstorage,growthof storagefungiwereobservedthatweremicroscopicallyidentified asbelongingtoPenicilliumsp.andAspergillussp.(Rodriguesetal., 2013).Thesefungiproduceenzymes,suchaslipases(EC3.1.1.3., triacylglycerolacylhydrolases)thatcatalyseoilhydrolysis.
Attheendoftheexperiment,theoilfromseedskeptunder92% RHreachedabout25%FFAwhiletheoilfromseedsstoredat75% humiditypresentedamuchloweracidityofabout8%.However, inourpreviousworkperformedwithJ.curcasseedscontaining
0.0 0.5 1.0 1.5 2.0 2.5 0 7 14 21 28 35 42 K2 32 Time (day) R.H.= 75% R.H.= 92% 0.0 0.1 0.2 0.3 0.4 0.5 0 7 14 21 28 35 42 K 27 0 Time (day) R.H.= 75 % R.H. = 92 %
Fig.2.Absorbancesat232nm(K232)andat270nm(K270)intheoilextractedfrom JatrophacurcasL.seedsstoredfor42daysat35◦Cunderdifferentrelativehumidity
values(RH=92%,RH=75%).
loweramounts ofgamma-tocopherol,lowerfinal acidityvalues werefound:17%FFAand1.2%after45daysofseedstorageat35◦C, at92%or75%RH,respectively(Rodriguesetal.,2013).Thehigher acidityintheoilwithhighergamma-tocopherolcontentmaybe explainedbyhigherlevelsoflipasesinseeds,eitherfrominternal orexternalorigin.
AnincreaseinFFAcontentofJatrophaseedoilduringstorageis alsoreportedbyotherauthors.Tadakittisarnetal.(2011)observed anincreaseinFFAinoilfromthreeJatrophaaccessionsfrom dif-ferentregionsofThailand,alongseedstorage.Alinearincreasein acidityfrom7.8to32.1%wasalsoobservedintheoilextractedfrom Jatrophaseedsstoredfor3months,at35◦CandunderaRHvarying from71to75%(Akowuahetal.,2012).AnincreaseofFFAcontent ofJatrophaoil,along72daysstorageofseeds,wasalsoreported (GuptaandRao,2008).
InastudybyWorangetal.(2008),FFAcontentincreasedwith thestoragedurationofJatrophaseedspackedinplasticmaterial. Theincrease inoilaciditywasalsoreportedbySushma(2014) whenJatrophaseedswerecollectedandstoredatroom temper-ature(openaircondition)for15months.
3.2. Oxidationproductsandgamma-tocopherolcontentinoil The evolution of oil oxidation in seeds along the 42 days experimentsat35◦C,underdifferentrelativehumidityvalues,is presentedinFig.2.
A linear increase in K232, related withthe presence of ini-tial products of oxidation, i.e. conjugated hydroperoxides, was observedalongtheexperiment,fortheoilinseedsstoredat75%RH (increaseof0.029absorbanceunits/day).TheK232valueincreased fasterintheoilextractedfromseedskeptat92%ofhumiditythan intheoilfromseedsstoredatlowerRH(75%),duringthefirsttwo weeksofstorage(increaseof0.059absorbanceunits/day).After14
Table1
Variationinfattyacidcomposition(%)oftheoilextractedfromtheseedsofJatrophastoredat35◦Cand75%RHover42days.C14:0(myristicacid),C16:0(palmiticacid),C16:1
(palmitoleicacid),C17:0(margaricacid),C17:1(heptadecanoicacid),C18:0(stearicacid),C18:1(oleicacid),C18:2(linoleicacid),C20:0(arachidicacid),C18:3(linolenic acid),C20:1(gadoleicacid),C22:0(behenic)andC24:0(lignocericacid).Standarddeviationslowerthan0.01arenotpresented.
Fattyacids Time(day)
0 7 14 21 28 35 42 C14:0 0.20 0.20 0.20 0.20 0.20 0.20 0.20 C15:0 0.10 0.10 0.10 0.20 0.10 0.10 0.10 C16:0 11.60 11.75±0.07 11.35±0.07 11.75±0.07 11.70 11.65 11.80 C16:1 0.60 0.60 0.60 0.60 0.60 0.60 0.60 C17:0 0.10 0.10 0.10 0.10 0.10 0.10 0.10 C17:1 0.10 0.10 0.10 0.10 0.10 0.10 0.10 C18:0 6.60 6.40 6.65±0.07 6.65±0.07 6.70 6.80 6.70 C18:1 41.2 40.5 41.25±0.07 41.65±0.21 41.2 41.8 41.3 C18:2 38.80 39.55±0.07 38.90 38.10±0.28 38.60 37.95±0.07 38.40 C18:3 0.20 0.20 0.20 0.20 0.20 0.20 0.20 C20:0 0.20 0.20 0.20 0.20 0.20 0.20 0.20 C20:1 0.10 0.10 0.10 0.10 0.10 0.10 0.10 C22:0 0.10 0.1 0.10 0.10 0.10 0.10 0.10 C24:0 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Table2
Variationinfattyacidcomposition(%)oftheoilextractedfromtheseedsofJatrophastoredat35◦Cand92%RHover42days.C14:0(myristicacid),C16:0(palmiticacid),C16:1 (palmitoleicacid),C17:0(margaricacid),C17:1(heptadecenoicacid),C18:0(stearicacid),C18:1(oleicacid),C18:2(linoleicacid),C20:0(arachidicacid),C18:3(linolenic acid),C20:1(gadoleicacid),C22:0(behenic)andC24:0(lignocericacid).Standarddeviationslowerthan0.01arenotpresented.
Fattyacids Time(days)
0 7 14 21 28 35 42 C14:0 0.20 0.20 0.20 0.20 0.20 0.20 0.20 C15:0 0.10 0.10 0.10 0.10 0.10 0.10 0.10 C16:0 11.60 11.55±0.07 10.95±0.07 11.60 11.80 11.50 11.80 C16:1 0.60 0.60 0.60 0.60 0.60 0.60 0.60 C17:0 0.10 0.10 0.10 0.10 0.10 0.10 0.10 C17:1 0.10 0.10 0.10 0.10 0.10 0.10 0.10 C18:0 6.60 6.65±0.07 6.60 6.70 6.60 6.60 6.70 C18:1 41.20 41.25±0.07 41.30 40.85±0.07 40.60 41.40 41.25±0.07 C18:2 38.80 38.75±0.07 39.35±0.07 39.05±0.07 39.20 38.70 38.45±0.07 C18:3 0.20 0.20 0.20 0.20 0.20 0.20 0.20 C20:0 0.20 0.20 0.20 0.20 0.20 0.20 0.20 C20:1 0.10 0.10 0.10 0.10 0.10 0.10 0.10 C22:0 0.10 0.10 0.10 0.10 0.10 0.10 0.10 C24:0 0.10 0.10 0.10 0.10 0.10 0.10 0.10
daysstorageanduntiltheendofexperiments,aslowerincreasein
K232wasobservedfortheoilfromseedsat92%RH.Thisis
prob-ablyduetothedecompositionofthehydroperoxidesinsmaller
molecules(finaloxidationproducts).Attheendoftheexperiments,
K232valuesweresimilarforbothoils.
TheK270values,relatedwiththepresenceoffinaloxidation
products(i.e.FFA,aldehydesandketones),increasedfrom0.07to
0.22inoilsfromseedsstoredatbothRH,duringthefirst21days
ofstorage.Fortheoilinseedsstoredat75%R.H.,K270remained
approximatelyconstantthereafter.However,inseedsstoredat92%
RH,alinearincreaseinK270wasobservedsubsequently,reaching
anabsorbancevalueofaround0.46after42daysofstorage.
Similar K232 and K270 values were obtained for the oil
fromseedsstoredat 75%humidity whencompared withthose
previouslyobtainedforJatrophaoilwithloweramountsof
gamma-tocopherol(89mg/kg)(Rodriguesetal.,2013).
Withrespecttotheoilsfromseedsstoredat92%RH,K232and K270valuesoftheoilwithhighercontentofgamma-tocopherol were1.5or2.8timeslowerthanthevaluesobservedfortheoil extractedfromseedsofthepreviousstudy,respectively(Rodrigues et al., 2013). It seems that gamma-tocopherol protects the oil againstoxidationprincipallyduringthesecondstageofoxidation wherehydroperoxidesarebrokendownintosecondaryproducts. Also,thisprotectiveeffectseemstobeparticularlyimportantifthe seedsarestoredunderhighhumidityenvironments.
Theevolutionoftheaveragegamma-tocopherolcontentinthe oil extracted from the seeds along the storage experiments is
Fig.3. Averagegamma-tocopherolcontentoftheoilextractedfromJatrophaseeds storedat35◦Cand75%or92%RHalong42days.Differentlettersindicatesignificant
differencesbasedonFisherLSDtest(p<0.05).
showninFig.3.Asignificantdecreaseingamma-tocopherol con-tent(p<0.05)wasobservedduringthecourseoftheexperimentfor bothrelativehumidities.Thisdecreasemayexplaintheincreasein oxidationproducts(relatedwithK232andK270values)intheoils, observedalong Jatrophaseedstorage.However,thedecreasein gamma-tocopherolcontentwasmorepronouncedat92%RHthan at75%RH(96%decreaseversus57%decreaseongamma-tocopherol content,after42daysofstorage).Probably,thismaybeascribedto thepresenceofhigheramountsofwaterwhichwillpromotethe
growthoffungithatwillproduceoxidativeenzymesresponsible forlipidoxidation.
Theantioxidantactivityoftocopherolsisnotonlyduetotheir abilitytodonatetheirphenolichydrogenstolipidfree-radicals,but canalsobeexplainedbytheirparticipationincertainside-reactions (Kulåsetal.,2002).
Thefollowingorderforrelativeantioxidantactivityofthe toco-pherolsinvivoisgenerallyaccepted:alpha>beta>gamma>sigma. However, when relative antioxidant activities were compared in vitro, in fats, oils, and lipoproteins, a reversed order was obtained (sigma>gamma∼beta>alpha) (Kamal-Eldin and Appelqvist,1996).Thereasonsbehindthisreversedorderarenot yetclearlyunderstoodbut the“absolute”and “relative”invitro activitiesofthetocopherolsdepend ontheirabsolutechemical reactivitiestowardshydroperoxyandotherfreeradicals,andalso onmanyotherpossiblesidereactions.Thesesidereactionsmay behighlypropagativeandtheirextentgreatlydependson tocoph-erolconcentrations,temperatureandlight,typeofsubstrateand solvent,andonotherchemicalspeciesactingasprooxidantsand synergistsinthesystem(Kamal-EldinandAppelqvist,1996).
Inourstudy,theeffectofgamma-tocopheroloccursinsidethe seed,along storage,andnotintheextractedoil. Thus,asimilar behaviourtothatobservedinvivosystemsistobeexpected.The effectoftocopherolsontheoxidativestabilityofvegetableoils dur-ingstoragehasbeenextensivelyevaluated.However,according toourknowledge,few works have reportedtheeffectof toco-pherolsontheoxidativestabilityofJatrophaoilduringseedstorage (Rodriguesetal.,2013).
Diwanietal.(2009)observedthattheadditionofnatural antiox-idants obtainedfromEgyptian Jatrophacrude rootextracts,on Jatrophaoilanditsbiodieselpromotedhigheroxidationstability thanthatobservedwiththeadditionofalpha-tocopherol.
Antioxidantsmayhavedifferenteffectsontheformationand decompositionofhydroperoxides.Inastudyonfishoilstability alongstorage,thetocopheroltype andconcentrationshowedto affectnotonlytheoverallformationofvolatilesecondary oxida-tionproducts,butalsothecompositionofthisgroupofoxidation products(Kulåsetal.,2002).Theeffectsofindividualtocopherols andtocopherolmixturesontheoxidativestabilityofcornoilwere evaluatedbyHuangetal.(1995).Inthisstudy,gamma-tocopherol showedtopromotetheformationofhydroperoxidesbut,whenin veryhighconcentrations(5g/kgoil),itstronglyinhibited hydroper-oxidedecomposition.Conversely,inthepresenceoftocopherols, therateofhydroperoxidesbreakdownandinductionoffurther oxi-dationwasmarkedlyinhibitedinrapeseedoilstoredat40◦Cinthe dark.Aconcentrationaslowas11mgofgamma-tocopherolper kgofrapeseedoilwasenoughtomarkedlyinhibithydroperoxide andsecondaryproductformation(Lampietal.,1997).The antioxi-dantpropertiesofalpha-andgamma-tocopherolsintheoxidation ofrapeseedoilat40◦C,inthedark,for16dayswasalso evalu-ated(Lampietal.,1999).Invitro,atconcentrationshigherthan 100mg/kg, gamma-tocopherolisbetterantioxidant than alpha-tocopherol.
3.3. Fattyacidcompositionofoils
ThefattyacidcompositionofJatrophaoilextractedfromthe seedsstoredat35◦Cunder75%or92%humidity,wasevaluated alongthe42daysstorageexperiments(Tables1and2).As previ-ouslyreported(Rodriguesetal.,2013),thisisahighlyunsaturated oil,richinoleic(c.a.41%)andlinoleic(c.a.38.8%)acidsanditalso contains11.6%ofpalmiticacidand6.6%ofstearicacid.Duringthe storageat35◦C,thefattyacidcompositionoftheoilfromseeds kepteitherat75%or92%ofhumidity,didnotsignificantlyvary throughoutthetest(Tables1and2).Fattyacidcompositionand theproportionsofdifferentfattyacidsofoilseedsduringstorageare
dependentonthedegradationrateofdifferentfattyacids(Khanand Shahidi,2000).InastudybyBaleˇsevi ´c-Tubi ´cetal.(2007),sunflower seedswerestoredunderuncontrolledconditionsfor12months. Duringthat periodoftime,theautooxidationoflipidsoccurred andledtomodificationsin fattyacidcomposition oftheseeds. Althougholeicacidcontentdidnotsignificantlyvary,linoleicacid contentwasdrasticallyreducedfrom23%,infreshsunflowerseeds, to5.49%attheendoftheexperiment.
4. Conclusions
ThestorageofJ.curcasL.seedsundertropicalclimateconditions of high temperature and humidity is difficult without affect-ingoilquality.However,thehighcontentofgamma-tocopherol (160mg/kgofoil)inJatrophaoilshowedtopromoteahigh resis-tancetooxidationduringseedstorage.
Alongstorage,adecreaseingamma-tocopherolcontentinthe oilwasobserved,whichmayexplaintheincreaseinoxidation prod-ucts.High humidityconditionspromotedthegrowthofstorage fungisuchasPenicilliumsp.andAspergillussp.,whichwerealso responsibleforoildegradation,viahydrolysisandenzymatic oxi-dation.
IfJ.curcasoilextractionfromtheseedsisnotpossible imme-diatelyafterharvest,J.curcasgenotypesrichingamma-tocopherol mustbechosen,inordertoavoidahighextentofoiloxidation.
Thecontrolofstorageconditionsoftheseeds(temperatureand humidity)isextremelyimportantinordertopreservethequality andtheyieldofJatrophaoil,witheconomicbenefits.
Acknowledgements
This work was supported by the Project “Development of advancedbiofuels”fundedbyFAIand Petrogal,Portugal,bythe StrategicProjectPEst-OE/AGR/UI0239/2014ofCEF,ForestResearch Centre, and the Strategic Project PEst-OE/AGR/UI0245/2014 of CEER,BiosystemsEngineering,tworesearchunitssupportedbythe nationalfundingofFCT—Fundac¸ãoparaaCiênciaeaTecnologia, Portugal.
References
AETSConsortium,February2013.Assessingtheimpactofbiofuelsproductionon developingcountriesfromthepointofviewofPolicyCoherencefor Develop-ment–Finalreport.
Akowuah,J.O.,Addo,A.,Kemausuor,F.,2012.Influenceofstoragedurationof Jat-rophacurcasseedonoilyieldandfreefattyacidcontent.J.Agric.Biol.Sci.7(1), 41–45.
Baleˇsevi ´c-Tubi ´c,S.,Tati ´c,M.,Miladinovi ´c,J.,Pucarevi ´c,M.,2007.Changesoffatty acidsandvigorofsunflowerseedduringnaturalaging.Helia30(47),61–68.
Choe,E.,Min,D.B.,2006.Mechanismsandfactorsforedibleoiloxidation.Compr. Rev.FoodSci.FoodSaf.5,169–186(InstituteofFoodTechnologists).
Diwani,G.E.,Rafie,S.E.,Hawash,S.,2009.Protectionofbiodieselandoilfrom degra-dationbynaturalantioxidantsofEgyptianJatropha.Int.J.Environ.Sci.Technol. 6(3),369–378.
Emanuel,N.M.,Lyaskovskaya,Y.N.,1967.TheInhibitionofFatOxidationProcesses. PergamonPressLtd.,HeadingtonHillHall,Oxford4&5FitzroySquare,London.
FAO,2008.Soaringfoodprices:facts,perspectives,impactsandactionsrequired. In:ProceedingsoftheHigh-LevelConferenceonWorldFoodSecurity:The Chal-lengesofClimateChangeandBioenergy,Rome,Italy.
Fuster,M.D.,Lampi,A.M.,Hopia, A.,Kamal-Eldin,A.,1998.Effectsofalfa-and gamma-tocopherolontheautoxidationofpurifiedsunflowertriacylglycerols. Lipids33,715–722.
Giibitz,G.M.,Mittelbach,M.,Trabi,M.,1999.Exploitationofthetropicaloilseed plant,JatrophacurcasL.Bioresour.Technol.67,73–82.
Greenspan,L.,1977.Humidityfixedpointsofbinarysaturatedaqueoussolutions.J. Res.Natl.Bur.Stand.Sect.A81,89–96.
Gupta,R.M.,Rao,D.G.,2008.Effectofstoragetimeonyieldandfreefattyacid(FFA) contentofrawJatrophaoil.In:32ndNationalSystemsConference(NSC2008), Roorkee,India,December17–19,pp.440–443.
Heller,J.,1996.Physicnut.JatrophacurcasL.Promotingtheconservationanduseof underutilizedandneglectedcrops.1.InstituteofPlantGeneticsandCropPlant Research,Gatersleben/InternationalPlantGeneticResourcesInstitute,Rome.
Huang,S.,Frankel,E.N.,German,J.B.,1995.Effectsofindividualtocopherolsand tocopherolmixturesontheoxidativestabilityofcornoiltriglycerides.J.Agric. FoodChem.43(9),2345–2350.
Jung,M.Y.,Min,D.B.,1990.Effectsof␣-,␥-,and␦-tocopherolsonoxidativestability ofsoybeanoil.J.FoodSci.55,1464–1465.
Kamal-Eldin,A.,2006.Effectoffattyacidsandtocopherolsontheoxidativestability ofvegetableoils.Eur.J.LipidSci.Technol.58,1051–1061.
Kamal-Eldin,A.,Appelqvist,L.Å.,1996.Thechemistryandantioxidantpropertiesof tocopherolsandtocotrienols.Lipids31,671–701.
Khan,M.A.,Shahidi,F.,2000.Oxidativestabilityofstrippedandnonstrippedborage andeveningprimroseoilsandtheiremulsionsinwater.J.Am.OilChem.Soc.77 (9),963–969.
King,A.J.,He,W.,Cuevas,J.A.,Freudenberger,M.,Ramiaramanana,D.,Graham,I.A., 2009.PotentialofJatrophacurcasasasourceofrenewableoilandanimalfeed. J.Exp.Bot.60(10),2897–2905.
Köppen,W.,Geiger,R.,1939.HandbuchderKlimatologie.Borntraeger,Berlin.
Krieger-Liszkay,A.,Trebst,A.,2006.Tocopherolisthescavengerofsingletoxygen producedbythetripletstatesofchlorophyllinthePSIIreactioncentre.J.Exp. Bot.57(8),1677–1684.
Kulås,E.,Olsen,E.,Ackman,R.G.,2002.Effectof␣-,␥-,and␦-tocopherolonthe distributionofvolatilesecondaryoxidationproductsinfishoil.Eur.J.LipidSci. Technol.104,520–529.
Kumar,A.,Sharma,S.,2008.Anevaluationofmultipurposeoilseedcropfor indus-trialuses(JatrophacurcasL.).Areview.Ind.Crop.Prod.28,1–10.
Lampi,A.M.,Hopia,A.,Piironen,V.,1997.Antioxidantactivityofminoramounts of ␥-tocopherol in natural triacylglycerols. J. Am. Oil Chem. Soc. 74, 549–555.
Lampi,A.M.,Kataja,L.,Kamal-Eldin,A.,Vieno,P.,1999.Antioxidantactivitiesof ␣-and␥-tocopherolsintheoxidationofrapeseedoiltriacylglycerols.JAOCS76(6), 749–755.
Liberalino,A.A.,Bambirra,E.A.,Moraes-Santos,T.,Vieira,E.C.,1988.Jatrophacurcas L.seeds:chemicalanalysisandtoxicity.Arq.Biol.Technol.31,539–550.
Mtinch,E.,Kiefer,J.,1986.DiePurgiernuB(JatrophacurcasL.–Botanik,Okologie, Anbau,Ernteprodukt,Verwendungsalternativen,wirtschaftlicheUberlegungen, Diplomarbeit.UniversitiitHohenheim.
Neely,W.C.,Martin,M.,Barker,S.A.,1988.Productsandrelativereactionratesofthe oxidationoftocopherolswithsingletmolecularoxygen.Photochem.Photobiol. 48,423–428.
Reinton,R.,Rogstad,A.,1981.Antioxidantactivityoftocopherolsandascorbicacid. J.FoodSci.46,970–971.
Rodrigues,J.,Miranda,I.,Gominho,J.,Vasconcelos,M.,Barradas,G.,Pereira,H., Bianchi-de-Aguiar,F.,Ferreira-Dias,S.,2013.Variabilityinoilcontentand compositionandstoragestabilityofseedsfromJatrophacurcasL.grownin Mozambique.Ind.CropsProd.50,828–837.
Schut,M.,Slingerland,M.,Locke,A.,2010.BiofueldevelopmentsinMozambique. Updateandanalysisofpolicy,potentialandreality.EnergyPolicy38,5151–5165.
Shahidi,F.,Zhong,Y.,2005.Lipidoxidation:measurementmethods.In:Fereidoon Shahidi(Ed.),Bailey’sIndustrialOilandFatProducts,vol.6,Sixthed.JohnWiley &SonsInc.
Sharma,G.D.,Gupta,S.N.,Khabiruddin,M.,1997.CultivationofJatrophacurcasas afuturesourceofhydrocarbonandotherindustrialproducts.In:Gubitz,G.M., Mittelbach,M.,Trabi,M.(Eds.),BiofuelsandIndustrialProductsfromJatropha curcas.DBVGraz,pp.19–21.
Smeets,E.M.W.,Faaij,A.P.C.,Lewandowski,I.M.,Turkenburg,W.C.,2007.A bottom-upassessmentandreviewofglobalbioenergypotentialsto2050.Prog.Energy Combust.Sci.33,56–106.
Sushma,2014.AnalysisofoilcontentofJatrophacurcasseedsunderstorage condi-tion.J.Environ.Biol.35,571–575.
Tadakittisarn,S.,Janchai,P.,Vaithanomsat,P.,Apiwatanapiwat,W.,2011.Effectof ripeningstageandtemperatureonfreefattyacidcontentofJatrophacurcasoil duringstorage.Nat.Sci.45,275–283.
VanAardt,M.,Duncan,S.E.,Long,T.E.,O’Keefe,S.F.,Marcy,J.E.,Sims,S.R.,2004.Effect ofantioxidantsonoxidativestabilityofediblefatsandoils:thermogravimetric analysis.J.Agric.FoodChem.52,587–591.
Vera-Castillo, Y.B., Cuevas,J.A.,Valenzuela-Zapata, A.G.,Urbano, B., González-Andrés,F.,2014.Biodiversityandindigenousmanagementoftheendangered non-toxicgermplasmofJatrophacurcasL.intheTotonacapan(Mexico),andthe implicationsforitsconservation.Genet.Resour.CropEvol.61,1263–1278.
Wink,M.,Koschmieder,C.,Sauerwein,M.,Sporer,F.,1997.PhorbolestersofJ. curcas—biologicalactivitiesandpotentialapplications.In:Gubitz,G.M., Mittel-bach,M.,Trabi,M.(Eds.),BiofuelsandIndustrialProductsfromJatrophacurcas. DBVGraz,pp.160–166.
Worang,R.L.,Dharmaputra,O.S.,Syarief,R.,Miftahudin,2008.Thequalityofphysic nut(JatrophacurcasL.)seedspackedinplasticmaterialduringstorage.Biotropia 15,25–36.
