Physical properties of carob bean (Ceratonia siliqua L.): An industrial gum yielding crop

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Industrial

Crops

and

Products

j o u r n al hom ep a ge :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

Physical

properties

of

carob

bean

(Ceratonia

siliqua

L.):

An

industrial

gum

yielding

crop

E. Karababa

a

_,

_Y.

_Cos¸

_kuner

b,∗

a_Department_of_Nutrition_and_Dietetics,_Mu˘gla_School_of_Health,_University_of_Mu˘gla,_Kötekli,_Mu˘gla_48000,_Turkey b_Department_of_Food_Engineering,_Faculty_of_Engineering,_University_of_{Karamano˘glu}_Mehmetbey,_Karaman_70200,_Turkey

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received24February2012 Receivedinrevisedform8May2012 Accepted8May2012

Keywords: Physicalproperties Carobbean Seedsizedistribution

a

b

s

t

r

a

c

t

Somephysicalpropertiesofcarobbean(CeratoniasiliquaL.) wereevaluatedand theapplicationof

thesepropertiesalsodiscussed.Thecarobbeanhasanaverageof13.8%(d.b.)moisturecontent.The

averageseedlength,width,thicknessandgeometricmeandiameterwere8.69mm,6.43mm,3.88mm,

and5.99mm,respectively.Theaverage1000seedweight,volumeandsurfaceareaofcarobbeanwere

158.56g,81.23mm3_and_96.22_mm2_,_while_the_sphericity_and_aspect_ratio_were_0.70_and_74.09%,

respec-tively.Theaveragebulkdensityofseedwas899kg/m3_while_the_true_density_was₁₃₆₄_kg/m3_,_and

thecorrespondingporositywas33.78%.Thegravimetricandvolumetricﬂowratesofcarobbeanswere

104g/sand115.37ml/s,respectively.Theaveragestaticanddynamicangleofreposevalueswerefound

31.20◦and23.80◦,respectively.Thestaticcoefﬁcientfrictionwasleastincaseofstainlesssteelsheet

whileitishighestforPVC.

1. Introduction

Thecarob(CeratoniasiliquaL.)isaperennialleguminous

ever-greentreenativetothecoastalregionsofMediterraneanbasinand

southwestAsia,andisconsideredtobeanimportantcomponent

ofvegetationforeconomicandenvironmentalreasons(Tunalıo˘glu

andÖzkaya,2003).Thescientiﬁcnameofthecarobtreederives

fromthe Greekkeras, “horn”, and Latinsiliqua, alluding tothe

hardnessand shapeofthepod.Common nameoriginatesfrom

Hebrewkharuvfromwhich arederivedkharoub(inArabic)and

mayincludealgarrobo(inSpanish),carob(inEnglish),keration(in

Greeek),kec¸iboynuzuorharnup(inTurkish),andisalsoknownSt.

John’sBread(BattleandTous,1997).Ithasbeencultivated

through-outtheMediterraneanregionforover4000years(Catarino,1993).

Carobseedinhistorywassealedwhenancientjewelersgotinto

thehabitofusingthemasweights.Onecarobseedwasthe

small-estweightforadiamond,andthecarobgaveitsnametothecarat.

Thecarobtreeisgrowingtoaheightof12–15m,withaproductive

lifespanofmorethanonehundredyears.

The annual production of carobpods is 374,800 to441,000

tonson200,000ha withvery variableyields dependingonthe

cultivar, region, and farming practices. Main carob bean

pro-ducerandexportercountriesareSpain,Italy,Portugal,Morocco,

Greece,CyprusandTurkey(Roukas,1994;Catarino,1993;Battle

andTous,1997;Raceetal.,1999;Tunalıo˘gluandÖzkaya,2003).

∗ Correspondingauthor.Tel.:+903382262000;fax:+903382262023. E-mailaddress:yalcincoskuner@kmu.edu.tr(Y.Cos¸kuner).

Currentworldproduction ofcarobseedaveragesapproximately

30,000ton/yearandmorethan95%ofthisproductionoriginates

intheMediterraneanRegion(CurtisandRace,1998).Total

Turk-ishproductionisabout15,000tons,whichiscollectedfromwild

treesastherearenocommercialcaroborchards.Theproduction

isconcentrated alongthecoastintheMediterranean(96%)and

theAegean(4%)regionscitiesthatnamedHatayto ˙Izmir.Themain

carobproducingprovincesareMersin(˙Ic¸el),Antalya,Mu˘gla,Adana,

BurdurandAydın(BattleandTous,1997;Tunalıo˘gluandÖzkaya,

2003).

Thetwomaincarobpodconstituentsarepulp(90%)andseeds

(10%)byweight.Carobpulpishigh(48–56%)intotalsugarcontent

thatincludemainlysucrose,glucose,fructoseandmaltose.In

addi-tionitcontainsabout18%celluloseandhemicellulose.Also,ripe

carobpodscontainalargeamountofcondensedtannins(16–20%,

d.b.). Onthe otherhand,carob seedconstituents areseed coat

(30–33%),endosperm(42–46%)andembryo(23–25%)byweight

(BattleandTous,1997).

Carob seeds are extremely hard and carobendosperm

con-tains30–40%byweightofgalactomannanthatisapolysaccharide

moleculecomposedmannoseandgalactosesugarunits.So,this

product is well knownas carob beangum and is mostly used

in the food industry (Catarino, 1993; Battle and Tous, 1997).

The compound is a valuable stabilizing and thickening

addi-tiveusedin thefoodprocessing,pharmaceutical,textile,paper,

andpetroleumindustries(BattleandTous,1997;Tunalıo˘gluand

Özkaya,2003).

Carob hasbeenneglected withrespecttoculturalpractices,

research and development.Apart from a few scientiﬁc studies

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Fig.1. Carob(CeratoniasiliquaL.)beans(a)andcharacteristicdimensions(b)(ZografakisandDasenakis,2002).

written by interested researchers references on this crop are

scarce.Traditionallyimportantmainproductsofcarobarepods,

seedgums and derived productslikecarobbean ﬂour,pekmez

(concentratedcarob syrup/molasses), health foods (as a

choco-latesubstitute),carobsyrup,andmedicinessuchaslaxativesand

diuretics(Eks¸iandArtık,1986;BattleandTous,1997;Yousifand

Alghzawi,2000;Tunalıo˘gluandÖzkaya,2003;Turhanetal.,2006; Dakiaet al.,2007;Bouzouitaetal.,2007; Bineretal., 2007).In

addition,they canbe used as a cheap carbohydrate sourcefor

ethanolproduction, yielding160gofethanol/kgofdrylegumes

(Roukas,1994).Inrecentyearinterestincarobshasbeenincreasing

becauseofa cheapsourceofvarious products.Some

investiga-tionsexploredcarobpodsasasubstrateforcitricacidproduction

(Roukas,1999)andasareadilyavailableandinexpensivematerial

fortheproductionofbioethanol(MakrisandKefalas,2004),while

carobextracthavebeenasubjectofstudiesfortheirinﬂuenceon

centralandperipheralbenzodiazepinereceptors(Avalloneetal.,

2002).

Incarobindustry,afterharvestingthepodsareusedafter

crush-ingtoseparateseedandpulp.Whencarobsarrivetotheplant,

moisturecontentis variable(10–20%)depending onharvesting

conditions.Toreducetomoisturecontenttoaround8–10%,pods

aredriedundershelterindryandventilatedplacestoavoidrotting.

Carobpodsarecrushedmechanicallyusingkibblerthentheyare

separatedfromtheseeds.Thecarobseedsaretransportedinbulkby

lorrytothegumfactories.Thekernelsaredifﬁculttoprocess,since

theseedcoatisveryhard.Kernelsarepeeledwithoutdamaging

theendospermandtheembryos(germs).Afterthepeelingprocess

theendospermcanbesplitfromthecotyledonsbecauseoftheir

differentfriability.Aftersplittingprocess,endospermisgroundon

rollermillstothedesiredparticlesizetoproducecarobbeangum

andthecarobgermmealisaby-productoftheseedprocessing

(BattleandTous,1997).

Physicalandengineering properties ofagriculturalcropsare

necessary for the designof equipment and the analysis of the

behavioroftheproductduringagriculturalandindustrialprocesses

such as handling, harvesting, transporting, threshing, cleaning,

crushing,sorting, dryingand storing.Tothebestof our

knowl-edge, there are no published data on physical properties of

carob seed (C. siliqua L.). The objective of this study was to

investigatethesomegeometric,gravimetricandengineering

prop-erties of thecarob seed with a view to obtaining information

required to ease the operations of seed extraction from the

pod.

2. Materialsandmethods

2.1. Samplepreparation

Bulkofsundriedcarobseeds(Fig.1)wereobtainedfroma

com-mercialsource(IncomA.S¸.,Mersin,Turkey).Theseedswerecleaned

manuallytoremoveallforeignmaterialandbrokenseeds.Moisture

contentofthebulkcarobseedswasdeterminedaccordingtoAOAC

approvedmethod(AOAC,1984).Allthephysicalpropertieswere

determinedatthenaturalmoisturecontentof13.8%(d.b.).Since

seedsizeplaysanimportantroleinhandling,processingand

stor-age,underapproximatelythesameoperatingconditions(Masoumi

andTabil,2003).

Thebulksamplewasclassiﬁedintothreecategories,namely,

small,mediumandlargebulkseedswerescreenedusing5–8mm

round-holesieves(Cos¸kuneretal.,2002).Materialretainedoneach

sievewascollectedseparatelytoyieldthreefractionsdifferentiated

byseedsizeandclassiﬁedintosmall(<6mm),medium(6–7mm)

andlarge(>7mm)categoriesbasedonthemajordiameterandtheir

frequencydistributionbynumberdeterminedandrecordedasfor

theirskewnessandkurtosis(Fig.2).

2.2. Physicalcharacteristics

Todeterminetheaveragesizeoftheseed,asampleofhundred

seedswasrandomlyselectedfromeach.Measurementsofthethree

majorperpendiculardimensionsoftheseedwerecarriedoutwith

adigitalcalipertoanaccuracyof0.01mm.Thegeometricmean

diameter(Dg)oftheseedswascalculatedbyusingthefollowing

relationship(Mohsenin,1980):

Dg=(LWT )1/3 (1)

whereListhelength,WisthewidthandTisthethicknessinmm.

Thesphericity,ofcarobbeanseedswascalculatedusingthe

followingformula(Mohsenin,1980):

= (LWT )

1/3

L (2)

Carob beanvolume and surface areavalues were calculated

accordingtoJainandBal(1997):

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0 5 10 15 20 25 30 35 40 L 6·42-6·88 6·88-7·34 7·34-7·79 7·79-8·25 8·25-8·71 8·71-9·16 9·16-9·62 W 4·93-5·11 5·11-5·30 5·30-5·48 5·48-5·67 5·67-5·85 5·85-6·04 6·04-6·22 T 3·15-3·45 3·45-3·76 3·76-4·06 4·06-4·36 4·36-4·67 4·67-4·97 4·97-5·27 5<D<6 Width Thickness F req u e n c y Di s tri bu ti on (% ) 0 5 10 15 20 25 30 35 40 45 50 L 7·85 - 8·25 8·25 - 8·66 8·66 - 9·07 9·07 - 9·48 9·48 - 9·89 9·89 - 10·30 10·30 - 10·70 W 5·68 - 5·90 5·90 - 6·12 6·12 - 6·34 6·34 - 6·55 6·55 - 6·77 6·77 - 6·99 6·99 - 7·21 T 3·04 - 3·30 3·30 - 3·57 3·57 - 3·83 3·83 - 4·10 4·10 - 4·36 4·36 - 4·63 4·63 - 4·89 6<D<7 Lenght Width Thickness F req ue nc y Di s tr ib u ti on (% ) 0 5 10 15 20 25 30 35 40 45 50 L 8·94 - 9·28 9·28 - 9·62 9·62 - 9·95 9·95 - 10·29 10·29 - 10·63 10·63 - 10·97 10·97 - 11·30 W 6·90 - 7·15 7·15 - 7·40 7·40 - 7·65 7·65 - 7·90 7·90 - 8·15 8·15 - 8·40 8·40 - 8·65 T 2·96 - 3·30 3·30 - 3·64 3·64 - 3·98 3·98 - 4·33 4·33 - 4·67 4·67 - 5·01 5·01 - 5·35 D<7 Lenght Width Thickness F req ue nc y D is tr ibut ion ( % )

Fig.2.Frequencydistributionfortheaxialdimensionsofthecarobseeds:L,W,T andDarelength,width,thicknessandsieveholediameter;respectively.

S= _2LBL₋2_B (4)

where

B=(WT )1/2 (5)

Theaspectratio,Rawascalculated(Altuntas¸etal.,2005)as

Ra=W_{L ×}100 (6)

The Sneedand Folktriangulardiagram methodwasusedto

obtainshapeindicesofcarobbeans(GrahamandMidgley,2000).

Particlesareenvisagedaslyinginthecontinuumbetweenblocks

(orspheres),slabs(discs,oblate)androds(prolate)whichmark

thecornersofthediagram(Fig.3).Thousandseedsweightwas

Fig.3. SneedandFolkdescriptiveparticleshapeclassesofungradedcarobbeans atmoisturecontentof13.81%(Cmeanscompact;P,platy;B,bladed;E,elongate;V, very).

determinedbycounting1000seedsandweighingtheminan

elec-tronicbalance.Thebulkdensityistheratioofthemasssampleof

theseedstoitstotalvolume.Itwasdeterminedbyﬁllinga1000ml

containerwithbeansfromaheightofabout15cm,strikingthe

toplevelandthenweighingthecontents(GuptaandDas,1997;

Dehspandeetal.,1993;Konaketal.,2002;PaksoyandAydin,2004).

Thetruedensitydeﬁnedastheratioofmassofthesampleto

itsseed volume,wasdeterminedusingthewater displacement

method.Fiftymilliliterofwaterwasplacedina100mlgraduated

measuringcylinderand5gseedswereimmersedinthatwater.

Owingtotheshortdurationoftheexperimentandthenatureof

theskinofthecarobseedwhichdidnotallowwatertobeabsorbed

easily,theseedswerenotcoatedtopreventmoistureadsorption.

Theamountofdisplacedwaterwasrecordedfromthegraduated

scaleofthecylinder.Theratioofweightofseedstothevolumeof

displacedwatergavethetruedensity(Olajideetal.,2000;Amin

etal.,2004).

Theporosity(ε)isthefractionofthespaceinthebulkgrain

whichisnotoccupiedbythegrain(ThompsonandIsaacs,1967).

Theporosityofbulkseedwascalculatedfromthevaluesoftrue

densityandbulkdensityusingtherelationshipgivenbyMohsenin

(1980)asfollows:

ε=

t−b

t

×100 (7)

wherebisthebulkdensityandtisthetruedensity.

FlowratesofsamplesweredoneaccordingtoSchüsseleand

Bauer-Brandl(2003).Afunnelwasﬁxedinaverticalposition.The

bottomopeningwasclosedimpermeably.Carobseedsampleswere

weighedandintroducedintothefunnel.Thefunnelwasopened

andthetimetheentirecarobseedsampleneededtoﬂowoutof

thefunnelmeasured.Gravimetricandvolumetricﬂowrateswere

expressedinsecondsper100gand100mlofsample(TheEuropean

Pharmacopoeia4,2002;SchüsseleandBauer-Brandl,2003).

To determine the dynamic angle of repose, a plywood box

measuring300mm×300mm×300mm,havingaremovablefront

panelwasused.Theboxwasﬁlledwiththeseedsatthedesired

moisturecontent,andthefrontpanelwasquicklyremoved,

allow-ingtheseedstoﬂowtotheirnaturalslope.Theangleofreposewas

calculatedfrommeasurementsofseedfreesurfacedepthsatthe

endoftheboxandmidwayalongtheslopedsurfaceand

horizon-taldistancefromtheendoftheboxtothismidpoint.Thismethod

hasbeenusedbyotherresearchers(Duttaetal.,1988;JainandBal,

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Thecoefﬁcientofstaticfrictionwasdeterminedwithrespectto

sixsurfaces:plywood,galvanizediron,aluminum,stainlesssteel,

kraft paper and polypropylene knitted bag. These are common

materialsusedfortransportation,storageandhandlingoperations

ofgrains,pulsesandseedsconstructionofstorageanddryingbins.

Ahollowmetalcylinder50mmdiameterand50mmhighandopen

atbothendswasﬁlledwiththeseedsatthedesiredmoisture

con-tentandplacedonanadjustabletiltingtablesuchthatthemetal

cylinderdoesnottouchthetablesurface.Thetiltingsurfacewas

raisedgraduallybymeansofascrewdeviceuntilthecylinderwith

seedsjuststartstoslidedown.Theangleofthesurfacewasread

fromascaleandthestaticcoefﬁcientoffrictionwastakenasthe

tangentof thisangle. Otherresearchershave usedthis method

forothergrainsandseeds(Duttaetal.,1988;Joshietal.,1993;

SinghandGoswami,1996;SutharandDas,1996).Thecoefﬁcient

offrictionwascalculatedfromthefollowingrelationship:

=tan ˛ (8)

whereisthecoefﬁcientoffrictionand˛istheangleoftiltin

degrees.

DatawereevaluatedusingtheStatisticaforWindowssoftware

packageandtheresultsofthetestperformedaregivenwiththe

meanvalue,minimumvalue,maximumvalueandstandard

devia-tion(SD)(StatSoft,2001).Also,theskewnessandkurtosisanalysis

wereusedtomeasurethedeviationofthedistributionfrom

sym-metryandtomeasurethepeakednessorﬂatnessofadistribution

comparedtothenormaldistribution,respectively.

3. Resultsanddiscussion

3.1. Geometricpropertiesofcarobseedanddimensional

relationships

Table1givesthemeanvaluesoftheparameterforcarobseed

classiﬁedunder three fractions. Around 45% of theseeds were

medium(widthbetween6.0and7.0mm),whileabout5%ofthe

seedsweresmaller(widthbetween5.0and6.0mm)and50%larger

(widthgreaterthan7.0mm).AscanbeseenfromTable1,

thick-nessesoftheseedswerenotchangedinallfractionsofthecarob

seeds.Thecarobseedlengthvaluesof100measurementsat13.81%

moisturecontentforsmall,mediumandlargefractionwerefound

tobe8.10,9.09and10.21mm,respectively.

Thelengthofcarobseedwashigherthanthosereportedfor

safﬂower(Baümleretal.,2006),ﬂaxseed(Cos¸kunerandKarababa,

2007)andwasfoundclosetosunﬂower(Guptaand Das,1997),

gunaseed(Aviaraetal.,1999),Africanaseed(AkaaimoandRaji,

2006).Howeverit was lower than those reportedfor karingda

(SutharandDas,1996),locustbeanseed(Ogunjimietal.,2002),

ediblesquash(PaksoyandAydin,2004).

Thewidthofcarobseedwashigherthanthosereportedfor

saf-ﬂower(Baümleretal.,2006),sunﬂower(GuptaandDas,1997),

gunaseed(Aviaraetal.,1999),ﬂaxseed(Cos¸kunerandKarababa,

2007)andlowerthanthosereportedforlocustbeanseed(Ogunjimi

etal.,2002),ediblesquash(PaksoyandAydin,2004).

Thethicknessofcarobseedwashigherthanthoseofsafﬂower

(Baümler et al.,2006),karingda (Sutharand Das,1996),edible

squash(PaksoyandAydin,2004).sunﬂower(GuptaandDas,1997),

gunaseed(Aviaraetal.,1999),ﬂaxseed(Cos¸kunerandKarababa,

2007)andlowerthantheseoflocustbeanseed(Ogunjimietal.,

2002),Africanaseed(AkaaimoandRaji,2006).

Theskewnessandkurtosisanalysisforthefrequency

distribu-tioncurveforthe100measurementstakenforeach dimension

arepresentedinTable1andshowninFig.2.Skewnessmeasures

thedeviationofthedistributionfromsymmetry.Iftheskewness

isclearlydifferentfrom0,thenthatdistributionisasymmetrical, Table

1 Size distribution of carob beans at moisture content of 13.8% (d.b.). Particulars Size categories Small seeds Medium seeds Large seeds Mean ± Std. dev. (min.–max.) Skewness Kurtosis Mean ± Std. dev. (min.–max.) Skewness Kurtosis Mean ± Std. dev. (min.–max.) Skewness Kurtosis Length (mm) 7.74 ± 0.55 (6.95–9.27) 0.705 0.468 8.84 ± 0.60 (8.05–10.37) 0.934 0.199 9.49 ± 0.45 (8.83–10.27) 0.329 − 1.249 Width (mm) 5.49 ± 0.24 (5.03–5.88) − 0.204 − 0.916 6.47 ± 0.21 (5.99–6.87) − 0.545 − 0.255 7.34 ± 0.26 (6.91–8.20) 1.080 2.675 Thickness (mm) 3.70 ± 0.44 (2.58–4.42) − 0.407 − 0.020 3.90 ± 0.35 (3.33–4.76) 0.516 − 0.140 4.05 ± 0.49 (3.26–5.15) 0.454 − 0.447 Geometric Mean Diameter (mm) 5.38 ± 0.24 (4.92–5.85) − 0.367 − 0.323 6.05 ± 0.19 (5.55–6.42) − 0.498 0.257 6.54 ± 0.28 (6.13–7.10) 0.598 − 0.714 Sphericity 0.70 ± 0.05 (0.54–0.80) − 0.686 1.583 0.69 ± 0.04 (0.60–0.77) − 0.335 − 0.017 0.69 ± 0.04 (0.61–0.77) − 0.032 − 0.023 Volume (mm 3) 58.36 ± 9.14 (39.79–75.70) − 0.212 − 0.530 81.64 ± 8.77 (62.28–98.34) 0.181 − 0.162 103.7 ± 15.93 (83.7–141.0) 0.770 − 0.251 Surface area (mm 2) 77.36 ± 7.10 (63.99–91.29) − 0.251 − 0.494 97.40 ± 6.37 (81.62–109.50) − 0.310 0.019 113.9 ± 10.25 (99.5–136.1) 0.693 − 0.526 Aspect ratio (%) 71.31 ± 6.00 (55.12–84.60) − 0.129 1.141 73.45 ± 4.54 (62.87–81.26) − 0.542 − 0.396 77.5 ± 3.73 (69.8–83.7) − 0.289 − 0.478

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content.

Particulars Mean±St.dev. Min.-max. r

Small L/W 1.41±0.12 1.18–1.81 −0.078 L/T 2.13±0.39 1.64–3.59 −0.442** L/M 66.64±10.74 53.61–98.20 0.019 W/M 47.14±5.78 37.41–61.65 0.506** T/M 31.44±2.59 26.82–36.27 0.807** Medium L/W 1.37±0.09 1.23–1.59 0.342 L/T 2.29±0.31 1.70–2.96 −0.459** L/M 53.58±5.04 45.23–63.82 0.235 W/M 39.21±2.86 33.45–44.97 0.496** T/M 23.59±1.94 18.35–27.30 0.531** Large L/W 1.29±0.06 1.19–1.43 0.347 L/T 2.38±0.34 1.80–3.15 −0.237 L/M 46.79±4.72 38.27–54.77 0.317 W/M 36.19±3.37 30.17–42.39 0.490** T/M 19.82±1.84 16.46–24.09 0.689** **_Signiﬁcant_at_1%_level.

whilenormaldistributionsareperfectlysymmetrical.Asimplied

bytheterm,theskewnessisameasureoftheextenttowhichthe

distributionoftherespectivevariableisskewedtotheleft

(nega-tivevalue)orright(positivevalue),relativetothestandardnormal

distribution(forwhichtheskewnessis0).Kurtosismeasuresthe

“peakedness”ofadistribution.Ifthekurtosisisclearlydifferent

than0,thenthedistributioniseitherﬂatterormorepeakedthan

normal;thekurtosisofthenormaldistributionis0.Thekurtosisis

ameasureofhow“wide”or“skinny”(“ﬂat”or“peaked”)the

distri-butionisfortherespectivevariable,relativetothestandardnormal

distribution(forwhichthekurtosisisequalto0).Thecoefﬁcients

ofcorrelationobtainedforbetweenthemaindimensionsandmass

(Table2)showedthat themassofcarobseedmostlyrelatedto

thicknessand widththanlength.Width,thicknessand

geomet-ricmeandiameterwaspositivelyandsigniﬁcantlycorrelatedwith

massforalldimensionalfractions.However,lengthofthecarob

seedwasnotsigniﬁcantlycorrelatedwithmass.

Thegeometricmeandiameteroftheallfractionresultedin

high-estcorrelationswithmass.Thesecorrelationsillustratedthatthe

geometricmeandiameterwasfoundthebestdimensional

param-eterforestimationofseedmass.Thefollowinggeneralexpressions

canbeusedtodescribe therelationshipsamonglength,width,

thicknessandunitmassvaluesofgradedcarobbean:

Ls=1.4.1 Ws=2.13 Ts=66.64Ms

forsmallcategorizedcarobbeans (9)

formediumcategorizedcarobbeans (10)

Ll=1.29 Wl=2.38 Tl=46.79 Ml

forlargecategorizedcarobbeans (11)

Individual measured values were projected onto triangular

diagramsby usingthetri-plot spread sheetmethodof Graham

andMidgley(2000).AscanbeseenfromFig.3,shapeindicesof

ungradedcarobbeansdependsontheirperpendiculardimensions

wereclassiﬁedinbladed(72%)andcompact-bladed(20%).These

resultsingood agreementwithsphericity (0.70)value ofcarob

beans.

3.2. Gravimetricandfrictionalproperties

Asummaryoftheresultsforallthemeasuredparametersthat

relatedwithgravimetricandfrictionalpropertiesofcarobseedsat

13.8%moisturecontentisgiveninTable3.Themeanone-thousand

seedweightwas115.34,165.88and194.45gforsmall,medium

andlargeseedsofcarob,respectively.One-thousandseedweight

ofcarobwashigherthanthoseofkaringda(SutharandDas,1996),

sunﬂower(GuptaandDas,1997),gunaseed(Aviaraetal.,1999),

2007),andlowerthanthoseoflocustbeanseed(Ogunjimietal.,

2002),ediblesquash(PaksoyandAydin,2004),andAfricanaseed

(AkaaimoandRaji,2006).

Thebulkdensitiesofsmall,mediumandlargecarobseedsare

decreasedlinearlyfromanaveragevalueof908–891kg/m3_._The

decreasein bulkdensityof carobseeddependsondimensional

change(small,mediumandlargeseeds)indicatesthattheincrease

ofvolumeintheseedsisgreaterthanweightatsamemoisture

content.Thebulkdensityofcarobseedwasfoundtobehigher

thanthat ofkaringda(SutharandDas,1996),sunﬂower(Gupta

andDas,1997),gunaseed(Aviaraetal.,1999),locustbeanseed (Ogunjimietal.,2002),ediblesquash(PaksoyandAydin,2004),

2007),ontheotherhandafricanaseeds(AkaaimoandRaji,2006)

showedthatsimilarbulkdensitytothoseofcarobseeds.

Allthedimensionalgroupsofcarobseedhavetruedensities

greaterthan 1000kg/m3 _(1248, ₁₃₇₂_and ₁₄₃₀_kg/m3 _for _small,

mediumandlargeseeds,respectively)whichimpliesthattheseeds

heavierthanwaterandthischaracteristiccanbeusedtodesigna

separationandcleaningequipmentfortheseedssincethelighter

Table3

Gravimetricandfrictionalpropertiesofcarobbeansatmoisturecontentof13.8%(d.b.).

Properties Smallseeds(D<6) Mediumseeds(6<D<7) Largeseeds(D>7)

One-thousandseedweight(g) 115.34 165.88 194.45

Bulkdensity(kg/m3₎ ₉₀₈ ₈₉₉ ₈₉₁

Truedensity(kg/m3₎ ₁₂₄₈ ₁₃₇₂ ₁₄₃₀

Porosity(%) 27.24 34.47 37.69

Flowrate

Volumetricﬂowrate(ml/s) 120.09 115.96 110.05

Gravimetricﬂowrate(g/s) 108.74 105.78 99.57

Angleofrepose(degree)

Filling 33.29 32.47 27.85 Emptying 27.75 23.96 22.41 Coefﬁcientoffriction Stainlesssteel 0.344 0.364 0.384 Galvanizediron 0.389 0.450 0.482 Knittedbag 0.504 0.488 0.488 Aluminum 0.349 0.399 0.409 PVC 0.532 0.499 0.472

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fractionswillﬂoat.Thetruedensitiesofcarobseedsatdifferentsize fractionwerehigherthanthoseofkaringda(SutharandDas,1996),

sunﬂower(GuptaandDas,1997),gunaseed(Aviaraetal.,1999),

locustbeanseed(Ogunjimietal.,2002),ediblesquash(Paksoyand

Aydin,2004),safﬂower(Baümleretal.,2006),ﬂaxseed(Cos¸kuner andKarababa,2007),andsimilartothatofafricanaseeds(Akaaimo andRaji,2006).

Porosityisthepropertyofseedthatdependsonitsbulkand

truedensityandthemagnitudeofvariationinporositydepends

onthesefactorsonly.AscanbeseenTable3,porosityvaluesof

carobseedsincreasedlinearlywithincreasingseeddimension.The

porosityvaluesofcarobseedswere27.24,34.47,and37.68atthe

small,medium,andlargefraction,respectively.Theseporosity

val-ueswerelowerthan thoseof karingda (Sutharand Das,1996),

safﬂower(Baümler etal.,2006),gunaseed(Aviaraetal.,1999),

locustbeanseed(Ogunjimietal.,2002)andmoreorlesssimilar

tothoseofediblesquash(PaksoyandAydin,2004),africanaseeds

(Akaaimo andRaji,2006),andsunﬂowerseeds(Guptaand Das, 1997).

Asimpledeﬁnitionofseedﬂowabilityistheabilityofaseed

toflow.Bythisdefinition,flowabilityissometimesthoughtofasa

onedimensionalcharacteristicofagrain,wherebymaterialscanbe

rankedonaslidingscalefromfreeﬂowingandnon-ﬂowing.

Unfor-tunately,thissimplisticviewlacksthescienceandunderstanding

sufﬁcientaddresstocommonproblemsencounteredbythe

equip-mentdesigner.Onlyﬂuidscanﬂow;bulksolidsundergravityforces

canfall,slideorroll,butagainstgravity.Therateofﬂowofgranular

solidsbygravitythroughacircularopeninginthebottomofabinis

dependentonthediameteroftheopeningaswellasonthe

proper-tiesofthesolidandisindependent,withinwidelimits,onthehead

orheightofthesolids.Fromastandpointofﬂowpatterns,thereare

basicallythreetypesofﬂowinsymmetricalgeometry:mass-ﬂow,

funnel-ﬂowandexpandedﬂow.Pertainingfoodsystems,

funnel-ﬂowbinsmaybeusedforgrains,pulses,oilseeds,andsoon,mainly

fortheapplicationoffeedingdirectlysuchmaterialstoprocessing,

suchasincerealsextrusionorcerealmilling(Ortega-Rivas,2005).

Inrecentyears,mostofgrainsarestoredconicalbottomsilosto

useinfuture.Toobtainandrecordofemptyingtimeofsilosunder

gravityforcesisveryimportant.Forthispurpose,weobtained

vol-umetricandgravimetricﬂowratevaluesofcarobseedfrommodel

silos.

Volumetricﬂowratevaluesofcarobseedswerefoundhigher

thangravimetricﬂowratevaluesatallfraction.Bothvolumetric

andgravimetricﬂowratedecreased,asseedsizeincreased.The

volumetricﬂowratesofcarobseedwerefound120.09,115.96,and

110.05ml/sandgravimetricﬂowrateswerefound108.74,105.78,

and99.57g/satthesmall,medium,andlargeseedsizefractions,

respectively.

Theﬁllingangleofrepose valueswereobtainedhigherthan

emptyingangleofreposevaluesinallcarobseedfraction.Asseed

sizeincreased,bothvaluesofﬁllingandemptyingangleofrepose

decreased.Thevaluesofemptyingangleofreposeofcarobseed

were27.75,23.96,and 22.41,and thevalues of ﬁlling angleof

reposewere33.29,32.47,and27.85at thesmall,medium,and

largefraction,respectively.Ogunjimietal.(2002)forlocustbean

seedAkaaimoand Raji(2006)forafricanaseed,and Paksoyand Aydin(2004)forediblesquash,andCos¸kunerandKarababa(2007)

forﬂaxseedreportedsimilarangleofreposevalues.Theseresults

werelowerthanthoseofkaringda(SutharandDas,1996),

sun-ﬂowerseed(GuptaandDas,1997),andgunaseed(Aviaraetal.,

1999).

Thestaticcoefﬁcientoffrictionofcarobseedwasevaluatedover

ﬁvedifferentsurfaces:stainlesssteel,galvanizediron,

polypropy-leneknittedbag,aluminumandPVC.Whileincreasingtrends(for

staticcoefﬁcientoffrictionvalues)obtainedforcarobseeddepends

onincreasingdimensiononthemetallicsurfaces(stainlesssteel,

galvanizedironandaluminum)anddecreasingstaticcoefﬁcient

of friction values obtainedon PVCand knitted bag. It is found

that thestatic coefﬁcient of friction is lowest against stainless

steel atallfractions. Thismayowingtothesmootherand

pol-ishedsurfaceofthestainlesssteelcompared othersheetsused.

Sameresultswerefoundpreviousstudy(Cos¸kunerandKarababa,

2007).PVCsurfacehadthehighestcoefﬁcientoffriction(0.532)

atthesmallfractionfollowedbyknittedbag(0.504),galvanized

iron(0.389),aluminum(0.349),andstainlesssteel(0.344).Onthe

otherhand,atthelargefraction,galvanizediron(0.482)hadthe

highestcoefﬁcientoffrictionfollowedby,PVC(0.472),knittedbag

(0.466),aluminum(0.409),andstainlesssteel(0384),respectively.

Thecoefﬁcientoffrictionforcarobseedwashigherthanthatof

kar-ingdaseed(SutharandDas,1996),quinoaseeds(Vilcheetal.,2003),

andediblesquash(PaksoyandAydin,2004)againstgalvanizediron

sheet.Ontheotherhand,carobseedsshowedthatlowerstatic

coef-ﬁcientoffrictiontothatofsunﬂowerseeds(GuptaandDas,1997),

sesameseed(Tunde-AkintundeandAkintunde,2004),andﬂaxseed

(Cos¸kunerandKarababa,2007)againstbothgalvanizedironand

stainlesssteelsheet,andﬂaxseed(Cos¸kunerandKarababa,2007)

againstaluminumsheetandpolypropyleneknittedbag.

4. Conclusion

Thefollowingconclusionsarerevealedfromtheinvestigationof

somephysicalpropertiesofcarobbean(C.siliquaL.)ataverageof

13.8%(d.b.)moisturecontent.Thefrequencydistributioncurvesof

theaxialdimensionstendanearlynormaldistribution.The

aver-ageseedlength,width,thicknessand geometricmeandiameter

were8.69mm,6.43mm,3.88mm,and5.99mm,respectively.The

average1000seedweight,volumeandsurfaceareaofcarobbean

were158.56g,81.23mm3_and_96.22_mm2_,_while_the_sphericity_and

aspectratiowere0.70and74.09%,respectively.Shapeindicesof

ungradedcarobbeansdependsontheirperpendiculardimensions

were classiﬁedin bladed(72%) and compact-bladed(20%). The

averagebulkdensityofseedwas0899kg/m3_while_the_true

den-sitywas1364kg/m3_,_and_the_{corresponding}_porosity_was_33.78%.

Theaveragegravimetricandvolumetricﬂowratesofcarobbeans

were104g/sand115.37ml/s,respectively.Theaverageﬁllingand

emptyingangleof reposevalueswerefound31.20◦ and23.80◦,

respectively.Thestaticcoefﬁcientoffrictiononﬁvedifferent

mate-rialshasbeenfoundoutand theresultsshowedthatthemean

valueofstaticcoefﬁcientfrictionwasleastincaseofstainlesssteel

sheet whileit is highestfor PVC.In summary, this paperdeals

withthephysicalpropertiesofindustrialgumproducingcropof

carobbeans,providingusefuldataforitspostharvesthandlingand

industrialprocessing.

Acknowledgement

AuthorsthanktoIncomA.S¸.(Mersin,Turkey)forthesupplying

ofrawcarobbeans.

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