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Industrial Crops and Products 42 (2013) 440–446

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Industrial Crops and Products

journa l homepage: www.elsevier .com/ locate / indcrop

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

E. Karababaa, Y. Cos kunerb,∗

a Department of NutritionandDietetics, Mu˘ gla School of Health, University of Mu˘ gla, Kötekli, Mu˘ gla 48000, Turkeyb Department of FoodEngineering, Faculty of Engineering, University of Karamano˘ glu Mehmetbey, Karaman 70200, Turkey

a r t i c l e i n f o

Article history:

Received 24 February 2012Received in revised form 8 May 2012Accepted 8 May 2012

Keywords:

Physical propertiesCarob beanSeed size distribution

a b s t r a c t

Some physical properties of carob bean (Ceratonia siliqua L.) were evaluated and the application of these properties also discussed. The carob bean has an average of 13.8% (d.b.) moisture content. Theaverage seed length, width, thickness and geometric mean diameter were 8.69 mm, 6.43 mm, 3.88 mm,and 5.99mm, respectively. The average 1000 seed weight, volume and surface area of carob bean were158.56 g, 81.23 mm3 and 96.22 mm2, while the sphericity and aspect ratio were 0.70 and 74.09%, respec-tively. The average bulk density of seed was 899 kg/m3 while the true density was 1364kg/m3 , andthe corresponding porosity was 33.78%. The gravimetric and volumetric flow rates of carob beans were104 g/s and 115.37 ml/s, respectively. The average static and dynamic angle of repose values were found31.20◦ and 23.80◦, respectively. The static coefficient friction was least in case of stainless steel sheetwhile it is highest for PVC.

© 2012 Elsevier B.V. All rights reserved.

1. Introduction

The carob (Ceratonia siliqua L.) is a perennial leguminous ever-

green tree native to the coastal regions of Mediterranean basin andsouthwest Asia, and is considered to be an important componentof vegetation for economic and environmental reasons (Tunalıogluand Özkaya, 2003). The scientific name of the carob tree derivesfrom the Greek keras, “horn”, and Latin siliqua, alluding to thehardness and shape of the pod. Common name originates fromHebrew kharuv from which are derived kharoub (in Arabic) andmay include algarrobo (in Spanish), carob (in English), keration (inGreeek), kec iboynuzu or harnup (in Turkish), and is also known St. John’s Bread (Battle and Tous, 1997). It has been cultivated through-out the Mediterranean region for over 4000 years (Catarino, 1993).Carob seed in history was sealed when ancient jewelers got intothe habit of using them as weights. One carob seed was the small-est weight for a diamond, and the carob gave its name to the carat.

The carob tree is growing to a height of 12–15m, with a productivelife span of more than one hundred years.

The annual production of carob pods is 374,800 to 441,000tons on 200,000ha with very variable yields depending on thecultivar, region, and farming practices. Main carob bean pro-ducer and exporter countries are Spain, Italy, Portugal, Morocco,Greece, Cyprus and Turkey (Roukas, 1994; Catarino, 1993; Battleand Tous, 1997; Race et al., 1999; Tunalıoglu and Özkaya, 2003).

∗ Corresponding author. Tel.: +90 338 226 2000; fax: +90 338 2262023.E-mail address: [email protected](Y. Cos kuner).

Current world production of carob seed averages approximately30,000ton/year and more than 95% of this production originates

in the Mediterranean Region (Curtis and Race, 1998). Total Turk-ish production is about 15,000tons, which is collected from wildtrees as there are no commercial carob orchards. The productionis concentrated along the coast in the Mediterranean (96%) andtheAegean (4%) regions cities that named Hatay to Izmir. The maincarob producingprovinces areMersin (Icel), Antalya, Mugla,Adana,Burdur and Aydın (Battle and Tous, 1997; Tunalıoglu and Özkaya,2003).

The two main carob pod constituents are pulp (90%) and seeds(10%) by weight. Carob pulp is high (48–56%)in total sugar contentthat include mainly sucrose, glucose, fructose and maltose. In addi-tion it contains about 18% cellulose and hemicellulose. Also, ripecarob pods contain a large amount of condensed tannins (16–20%,d.b.). On the other hand, carob seed constituents are seed coat(30–33%), endosperm (42–46%) and embryo (23–25%) by weight(Battle and Tous, 1997).

Carob seeds are extremely hard and carob endosperm con-tains 30–40% by weight of galactomannan that is a polysaccharidemolecule composed mannose and galactose sugar units. So, thisproduct is well known as carob bean gum and is mostly usedin the food industry (Catarino, 1993; Battle and Tous, 1997).The compound is a valuable stabilizing and thickening addi-tive used in the food processing, pharmaceutical, textile, paper,and petroleum industries (Battle and Tous, 1997; Tunalıoglu andÖzkaya, 2003).

Carob has been neglected with respect to cultural practices,research and development. Apart from a few scientific studies

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E. Karababa, Y. Coskuner / Industrial Crops andProducts 42 (2013) 440–446 441

Fig. 1. Carob (Ceratonia siliqua L.) beans (a)and characteristic dimensions (b)(Zografakis and Dasenakis, 2002).

written by interested researchers references on this crop are

scarce. Traditionally important main products of carob are pods,seed gums and derived products like carob bean flour, pekmez(concentrated carob syrup/molasses), health foods (as a choco-late substitute), carob syrup, and medicines such as laxatives anddiuretics (Eksi and Artık, 1986; Battle and Tous, 1997; Yousif andAlghzawi, 2000; Tunalıoglu and Özkaya, 2003; Turhan et al., 2006;Dakia et al., 2007; Bouzouita et al., 2007; Biner et al., 2007). Inaddition, they can be used as a cheap carbohydrate source forethanol production, yielding 160 g of ethanol/kg of dry legumes(Roukas, 1994). In recentyear interest in carobshas beenincreasingbecause of a cheap source of various products. Some investiga-tions explored carob pods as a substrate for citric acid production(Roukas, 1999) and as a readily available and inexpensive materialfor the production of bioethanol (Makris and Kefalas, 2004), while

carob extract have been a subject of studies for their influence oncentral and peripheral benzodiazepine receptors (Avallone et al.,2002).

In carob industry, after harvesting the pods areused after crush-ing to separate seed and pulp. When carobs arrive to the plant,moisture content is variable (10–20%) depending on harvestingconditions. To reduce to moisture content to around 8–10%, podsaredried under shelter in dryand ventilated placesto avoid rotting.Carob pods are crushed mechanically using kibbler then they areseparatedfromtheseeds.Thecarobseedsaretransportedinbulkbylorry to the gum factories. The kernels are difficult to process, sincethe seed coat is very hard. Kernels are peeled without damagingthe endosperm and the embryos (germs). After the peeling processthe endosperm can be split from the cotyledons because of their

different friability. After splitting process, endosperm is ground onroller mills to the desired particle size to produce carob bean gumand the carob germ meal is a by-product of the seed processing(Battle and Tous, 1997).

Physical and engineering properties of agricultural crops arenecessary for the design of equipment and the analysis of thebehavior of the product duringagricultural and industrial processessuch as handling, harvesting, transporting, threshing, cleaning,crushing, sorting, drying and storing. To the best of our knowl-edge, there are no published data on physical properties of carob seed (C. siliqua L.). The objective of this study was toinvestigate the some geometric, gravimetric and engineeringprop-erties of the carob seed with a view to obtaining informationrequired to ease the operations of seed extraction from thepod.

2. Materials and methods

2.1. Sample preparation

Bulkof sun dried carob seeds (Fig. 1) were obtained from a com-mercial source (Incom A.S .,Mersin,Turkey).The seeds were cleanedmanuallyto removeall foreign materialand brokenseeds. Moisturecontentof the bulk carob seeds was determined according to AOACapproved method (AOAC, 1984). All the physical properties weredetermined at the natural moisture content of 13.8% (d.b.). Sinceseed size plays an important role in handling, processing and stor-age, under approximately the same operating conditions (Masoumiand Tabil, 2003).

The bulk sample was classified into three categories, namely,small, medium and large bulk seeds were screened using 5–8mm

round-hole sieves(Cos kuner et al., 2002). Material retained on eachsievewas collected separatelyto yieldthree fractions differentiatedby seed size and classified into small (<6 mm), medium (6–7mm)andlarge(>7mm) categories based onthe majordiameter andtheirfrequency distribution by number determined and recorded as fortheir skewness and kurtosis (Fig. 2).

2.2. Physical characteristics

To determine the average size of the seed, a sample of hundredseeds wasrandomlyselectedfrom each. Measurements of thethreemajor perpendicular dimensions of the seed were carried out witha digital caliper to an accuracy of 0.01mm. The geometric meandiameter (D g ) of the seeds was calculated by using the following

relationship (Mohsenin, 1980):

D g = (LWT )1/3 (1)

where L is the length,W is the width and T is the thickness in mm.The sphericity, of carob bean seeds was calculated using the

following formula (Mohsenin, 1980):

=(LWT )1/3

L (2)

Carob bean volume and surface area values were calculatedaccording to Jain and Bal (1997):

V =B2L2

6(2L−

B)

(3)



442 E. Karababa, Y. Coskuner / Industrial Crops andProducts 42 (2013) 440–446

0

5

10

15

20

25

30

35

40

45

50

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

Lenght

Width

Thickness

F r e q u e n c y D i s t r i b u t i o n ( % )

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 r e q u e n c y

D i s t r i b u t i o n ( % )

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 r e q u e n c y D i s t r i b u t i o n

( % )

Fig. 2. Frequency distribution for the axial dimensions of the carob seeds: L, W , T and D are length, width, thickness and sieve hole diameter; respectively.

S =BL2

2L− B (4)

where

B = (WT )1/2 (5)

The aspect ratio, Ra was calculated (Altuntas et al., 2005) as

Ra =W

L × 100 (6)

The Sneed and Folk triangular diagram method was used toobtain shape indices of carob beans (Graham and Midgley, 2000).Particles are envisaged as lying in the continuum between blocks(or spheres), slabs (discs, oblate) and rods (prolate) which mark

the corners of the diagram (Fig. 3). Thousand seeds weight was

Fig. 3. Sneed and Folk descriptive particle shape classes of ungraded carob beansat moisture content of 13.81% (C means compact; P, platy;B, bladed; E, elongate;V,very).

determined by counting 1000 seeds and weighing them in an elec-

tronic balance. The bulk density is the ratio of the mass sample of theseeds to its total volume. It was determined by filling a 1000 mlcontainer with beans from a height of about 15cm, striking thetop level and then weighing the contents (Gupta and Das, 1997;Dehspande et al., 1993; Konak et al., 2002; Paksoyand Aydin,2004).

The true density defined as the ratio of mass of the sample toits seed volume, was determined using the water displacementmethod. Fifty milliliter of water was placed in a 100 ml graduatedmeasuring cylinder and 5g seeds were immersed in that water.Owing to the short duration of the experiment and the nature of theskinof the carob seed which did not allow waterto be absorbedeasily, the seeds were not coated to prevent moisture adsorption.The amount of displaced water was recorded from the graduatedscale of the cylinder. The ratio of weight of seeds to the volume of

displaced water gave the true density (Olajide et al., 2000; Aminet al., 2004).The porosity (ε) is the fraction of the space in the bulk grain

which is not occupied by the grain (Thompson and Isaacs, 1967).The porosity of bulk seed was calculated from the values of truedensity and bulk density using the relationship given by Mohsenin(1980) as follows:

ε =

t − bt

× 100 (7)

where b is the bulk density and t is the true density.Flow rates of samples were done according to Schüssele and

Bauer-Brandl (2003). A funnel was fixed in a vertical position. Thebottomopening was closed impermeably. Carob seed samples were

weighed and introduced into the funnel. The funnel was openedand the time the entire carob seed sample needed to flow out of the funnel measured. Gravimetric and volumetric flow rates wereexpressedinsecondsper100gand100mlofsample(The EuropeanPharmacopoeia 4, 2002; Schüssele and Bauer-Brandl, 2003).

To determine the dynamic angle of repose, a plywood boxmeasuring 300mm×300mm×300mm, having a removable frontpanel was used. The box was filled with the seeds at the desiredmoisture content, and the front panel was quickly removed, allow-ing the seedsto flow to their natural slope. The angle of repose wascalculated from measurements of seed free surface depths at theend of the box and midway along the sloped surface and horizon-tal distance from the end of the box to this midpoint. This methodhas been used by other researchers (Duttaet al., 1988; Jain and Bal,

1997; Shepherd and Bhardwaj, 1986; Singh and Goswami, 1996).




The coefficient of static friction was determined with respect tosix surfaces: plywood, galvanized iron, aluminum, stainless steel,kraft paper and polypropylene knitted bag. These are commonmaterials used for transportation, storage and handling operationsof grains, pulses and seeds construction of storage and drying bins.A hollowmetal cylinder 50mm diameterand 50mm highand openat both ends was filled with the seeds at the desired moisture con-tent and placed on an adjustable tilting table such that the metalcylinder does not touch the table surface. The tilting surface wasraised gradually by means of a screw device until thecylinder withseeds just starts to slide down. The angle of the surface was readfrom a scale and the static coefficient of friction was taken as thetangent of this angle. Other researchers have used this methodfor other grains and seeds (Dutta et al., 1988; Joshi et al. , 1993;Singh and Goswami, 1996; Suthar and Das, 1996). The coefficientof friction was calculated from the following relationship:

= tan ˛ (8)

where is the coefficient of friction and ˛ is the angle of tilt indegrees.

Data were evaluated using the Statistica for Windows softwarepackage and the results of the test performed are given with the

mean value, minimum value, maximum value and standard devia-tion (SD) (StatSoft, 2001). Also, the skewness and kurtosis analysiswere used to measure the deviation of the distribution from sym-metry and to measure the peakedness or flatness of a distributioncompared to the normal distribution, respectively.

3. Results and discussion

3.1. Geometric properties of carob seed and dimensional

relationships

Table 1 gives the mean values of the parameter for carob seedclassified under three fractions. Around 45% of the seeds weremedium (width between 6.0 and 7.0 mm), while about 5% of the

seeds were smaller (width between 5.0 and6.0 mm) and 50% larger(width greater than 7.0 mm). As can be seen from Table 1, thick-nesses of the seeds were not changed in all fractions of the carobseeds.The carob seed length valuesof 100 measurements at 13.81%moisture content for small, medium and large fraction were foundto be 8.10, 9.09 and 10.21 mm, respectively.

The length of carob seed was higher than those reported forsafflower (Baümler et al., 2006), flaxseed (Cos kuner and Karababa,2007) and was found close to sunflower (Gupta and Das, 1997),guna seed (Aviara et al., 1999), Africana seed (Akaaimo and Raji,2006). However it was lower than those reported for karingda(Suthar and Das, 1996), locust bean seed (Ogunjimi et al., 2002),edible squash (Paksoy and Aydin, 2004).

The width of carob seed was higher than those reported for saf-

flower (Baümler et al., 2006), sunflower (Gupta and Das, 1997),guna seed (Aviara et al., 1999), flaxseed (Cos kuner and Karababa,2007) andlowerthanthosereportedforlocustbeanseed(Ogunjimiet al., 2002), edible squash (Paksoy and Aydin, 2004).

The thickness of carob seed was higher than those of safflower(Baümler et al., 2006), karingda (Suthar and Das, 1996), ediblesquash(Paksoyand Aydin,2004). sunflower (Gupta andDas, 1997),guna seed (Aviara et al., 1999), flaxseed (Cos kuner and Karababa,2007) and lower than these of locust bean seed (Ogunjimi et al.,2002), Africana seed (Akaaimo and Raji, 2006).

The skewness and kurtosis analysis for the frequency distribu-tion curve for the 100 measurements taken for each dimensionare presented in Table 1 and shown in Fig. 2. Skewness measuresthe deviation of the distribution from symmetry. If the skewness

is clearly different from 0, then that distribution is asymmetrical, T

a b l e

1

S i z e d i s t r i b u t i o n o f c a r o b b e a n s a t m o i s t u r e c o n t e

n t o f 1 3 . 8

% ( d . b . ) .

P a r t i c u l a r s

S i z e c a t e g o r i e s

S m a l l s e e d

s

M e d i u m s e e d s

L a r g e s e e d s

M e a n ± S t d . d e v . ( m

i n . – m a x . )

S k e w n e s s

K u r t o s i s

M e a n ±

S t d . d e v . ( m

i n . – m a x . )

S k e w n e

s s

K u r t o s i s

M e a n ±

S t d . d e v . ( m

i n . – m a x . )

S k e w n e s s

K u r t o s i s

L e n g t h ( m m )

7 . 7

4 ± 0

. 5 5 ( 6 . 9

5 – 9 . 2

7 )

0 . 7

0 5

0 . 4

6 8

8 . 8

4 ±

0 . 6

0 ( 8 . 0

5 – 1 0 . 3

7 )

0 . 9

3 4

0 . 1

9 9

9 . 4

9 ±

0 . 4

5 ( 8 . 8

3 – 1 0 . 2

7 )

0 . 3

2 9

− 1 . 2

4 9

W i d t h ( m m )

5 . 4

9 ± 0

. 2 4 ( 5 . 0

3 – 5 . 8

8 )

− 0 . 2

0 4

− 0 . 9

1 6

6 . 4

7 ±

0 . 2

1 ( 5 . 9

9 – 6 . 8

7 )

− 0 . 5

4 5

− 0 . 2

5 5

7 . 3

4 ±

0 . 2

6 ( 6 . 9

1 – 8 . 2

0 )

1 . 0

8 0

2 . 6

7 5

T h i c k n e s s ( m m )

3 . 7

0 ± 0

. 4 4 ( 2 . 5

8 – 4 . 4

2 )

− 0 . 4

0 7

− 0 . 0

2 0

3 . 9

0 ±

0 . 3

5 ( 3 . 3

3 – 4 . 7

6 )

0 . 5

1 6

− 0 . 1

4 0

4 . 0

5 ±

0 . 4

9 ( 3 . 2

6 – 5 . 1

5 )

0 . 4

5 4

− 0 . 4

4 7

G e o m e t r i c M e a n D i a m e t e r ( m m )

5 . 3

8 ± 0

. 2 4 ( 4 . 9

2 – 5 . 8

5 )

− 0 . 3

6 7

− 0 . 3

2 3

6 . 0

5 ±

0 . 1

9 ( 5 . 5

5 – 6 . 4

2 )

− 0 . 4

9 8

0 . 2

5 7

6 . 5

4 ±

0 . 2

8 ( 6 . 1

3 – 7 . 1

0 )

0 . 5

9 8

− 0 . 7

1 4

S p h e r i c i t y

0 . 7

0 ± 0

. 0 5 ( 0 . 5

4 – 0 . 8

0 )

− 0 . 6

8 6

1 . 5

8 3

0 . 6

9 ±

0 . 0

4 ( 0 . 6

0 – 0 . 7

7 )

− 0 . 3

3 5

− 0 . 0

1 7

0 . 6

9 ±

0 . 0

4 ( 0 . 6

1 – 0 . 7

7 )

− 0 . 0

3 2

− 0 . 0

2 3

V o l u m e ( m m 3 )

5 8 . 3

6 ± 9

. 1 4 ( 3 9 . 7

9 – 7 5 . 7

0 )

− 0 . 2

1 2

− 0 . 5

3 0

8 1 . 6

4 ±

8 . 7

7 ( 6 2 . 2

8 – 9 8 . 3

4 )

0 . 1

8 1

− 0 . 1

6 2

1 0 3 . 7

±

1 5 . 9

3 ( 8 3 . 7 – 1 4 1 . 0 )

0 . 7

7 0

− 0 . 2

5 1

S u r f a c e a r e a ( m m 2 )

7 7 . 3

6 ± 7

. 1 0 ( 6 3 . 9

9 – 9 1 . 2

9 )

− 0 . 2

5 1

− 0 . 4

9 4

9 7 . 4

0 ±

6 . 3

7 ( 8 1 . 6

2 – 1 0 9 . 5

0 )

− 0 . 3

1 0

0 . 0

1 9

1 1 3 . 9

±

1 0 . 2

5 ( 9 9 . 5 – 1 3 6 . 1 )

0 . 6

9 3

− 0 . 5

2 6

A s p e c t r a t i o ( % )

7 1 . 3

1 ± 6

. 0 0 ( 5 5 . 1

2 – 8 4 . 6

0 )

− 0 . 1

2 9

1 . 1

4 1

7 3 . 4

5 ±

4 . 5

4 ( 6 2 . 8

7 – 8 1 . 2

6 )

− 0 . 5

4 2

− 0 . 3

9 6

7 7 . 5

±

3 . 7

3 ( 6 9 . 8 – 8 3 . 7

)

− 0 . 2

8 9

− 0 . 4

7 8




Table 2

Ratios and coefficient of correlation (r ) values of seed dimensions at 13.8%moisturecontent.

Particulars Mean±St. dev. Min.-max. r

Small L/W 1.41 ± 0.12 1.18–1.81 −0.078L/T 2.13 ± 0.39 1.64–3.59 −0.442**

L/M 66.64 ± 10.74 53.61–98.20 0.019W/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 0.342L/T 2.29 ± 0.31 1.70–2.96 −0.459**

L/M 53.58 ± 5.04 45.23–63.82 0.235W/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 0.347L/T 2.38 ± 0.34 1.80–3.15 −0.237L/M 46.79 ± 4.72 38.27–54.77 0.317W/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.

while normal distributions are perfectly symmetrical. As impliedby the term, the skewness is a measure of the extent to which thedistribution of the respective variable is skewed to the left (nega-

tive value) or right (positive value), relative to the standard normaldistribution (for which the skewness is 0). Kurtosis measures the“peakedness” of a distribution. If the kurtosis is clearly differentthan 0, then the distribution is either flatter or more peaked thannormal; the kurtosis of the normal distribution is 0. The kurtosis isa measure of how “wide” or “skinny” (“flat” or “peaked”) the distri-butionis forthe respective variable,relativeto thestandard normaldistribution (for which the kurtosis is equal to 0). The coefficientsof correlation obtained for between the main dimensions and mass(Table 2) showed that the mass of carob seed mostly related tothickness and width than length. Width, thickness and geomet-ric mean diameter was positively and significantly correlated withmass for all dimensional fractions. However, length of the carobseed was not significantly correlated with mass.

Thegeometricmeandiameteroftheallfractionresultedinhigh-est correlations with mass. These correlations illustrated that thegeometric mean diameter was found the best dimensional param-eter for estimation of seed mass. The following general expressionscan be used to describe the relationships among length, width,thickness and unit mass values of graded carob bean:

Ls = 1.4.1 W s = 2.13 T s = 66.64M s

for small categorized carob beans (9)

Lm = 1.37 W m = 2.29 T m = 53.58 M m

for medium categorized carob beans (10)

Ll = 1.29 W l = 2.38 T l = 46.79 M l

for large categorized carob beans (11)

Individual measured values were projected on to triangulardiagrams by using the tri-plot spread sheet method of Grahamand Midgley (2000). As can be seen from Fig. 3, shape indices of ungraded carob beans depends on their perpendicular dimensionswere classified in bladed (72%) and compact-bladed (20%). Theseresults in good agreement with sphericity (0.70) value of carobbeans.

3.2. Gravimetric and frictional properties

A summary of the results for all the measured parameters thatrelated with gravimetric and frictional properties of carob seeds at13.8% moisture content is given in Table 3. The mean one-thousand

seed weight was 115.34, 165.88 and 194.45g for small, mediumand large seeds of carob, respectively. One-thousand seed weightof carob was higher than those of karingda (Suthar and Das, 1996),sunflower (Gupta and Das, 1997), guna seed (Aviara et al., 1999),safflower (Baümler et al., 2006), flaxseed (Cos kuner and Karababa,2007), and lower than those of locust bean seed (Ogunjimi et al.,2002), edible squash (Paksoy and Aydin, 2004), and Africana seed(Akaaimo and Raji, 2006).

The bulk densities of small, medium and large carob seeds aredecreased linearly from an average value of 908–891 kg/m3. Thedecrease in bulk density of carob seed depends on dimensionalchange (small, medium and large seeds) indicates that the increaseof volume in the seeds is greater than weight at same moisturecontent. The bulk density of carob seed was found to be higher

than that of karingda (Suthar and Das, 1996), sunflower (Guptaand Das, 1997), guna seed (Aviara et al., 1999), locust bean seed(Ogunjimi et al., 2002), edible squash (Paksoy and Aydin, 2004),safflower (Baümler et al., 2006), flaxseed (Cos kuner and Karababa,2007), on the other hand africana seeds (Akaaimo and Raji, 2006)showed that similar bulk density to those of carob seeds.

All the dimensional groups of carob seed have true densitiesgreater than 1000 kg/m3 (1248, 1372 and 1430kg/m3 for small,medium andlargeseeds,respectively) which implies that the seedsheavier than water and this characteristic can be used to design aseparation and cleaning equipment for the seeds since the lighter

Table 3

Gravimetric and frictional properties of carob beans at moisture content of 13.8%(d.b.).

Properties Small seeds (D< 6) Medium seeds (6 <D< 7) Large seeds (D> 7)

One-thousand seed weight (g) 115.34 165.88 194.45Bulk density (kg/m3) 908 899 891True density (kg/m3) 1248 1372 1430Porosity (%) 27.24 34.47 37.69Flow rate

Volumetric flow rate (ml/s) 120.09 115.96 110.05Gravimetric flow rate (g/s) 108.74 105.78 99.57

Angle of repose (degree)Filling 33.29 32.47 27.85Emptying 27.75 23.96 22.41

Coefficient of frictionStainless steel 0.344 0.364 0.384Galvanized iron 0.389 0.450 0.482Knitted bag 0.504 0.488 0.488Aluminum 0.349 0.399 0.409PVC 0.532 0.499 0.472




fractionswill float. Thetrue densities of carob seeds at differentsizefraction were higher than those of karingda (Suthar and Das, 1996),sunflower (Gupta and Das, 1997), guna seed (Aviara et al., 1999),locust bean seed (Ogunjimi et al., 2002), edible squash (Paksoy andAydin, 2004), safflower (Baümler et al., 2006), flaxseed (Cos kunerand Karababa, 2007), and similar to that ofafricanaseeds (Akaaimoand Raji, 2006).

Porosity is the property of seed that depends on its bulk andtrue density and the magnitude of variation in porosity dependson these factors only. As can be seen Table 3, porosity values of carob seeds increased linearly with increasing seed dimension. Theporosity values of carob seeds were 27.24, 34.47, and 37.68 at thesmall, medium, and large fraction, respectively. These porosity val-ues were lower than those of karingda (Suthar and Das, 1996),safflower (Baümler et al., 2006), guna seed (Aviara et al., 1999),locust bean seed (Ogunjimi et al., 2002) and more or less similarto those of edible squash (Paksoy and Aydin, 2004), africana seeds(Akaaimo and Raji, 2006), and sunflower seeds (Gupta and Das,1997).

A simple definition of seed flowability is the ability of a seedto flow. By this definition, flowability is sometimes thought of as aonedimensional characteristicof a grain,whereby materials canberanked on a sliding scale from free flowing and non-flowing. Unfor-tunately, this simplistic view lacks the science and understandingsufficient address to common problems encountered by the equip-ment designer.Only fluids canflow;bulk solidsundergravity forcescan fall, slide orroll, but againstgravity. The rate of flow ofgranularsolids bygravity through a circularopening inthe bottom ofa bin isdependent on thediameter ofthe opening aswellas on the proper-ties of the solid and is independent, within wide limits,on theheador height of the solids. From a standpoint of flowpatterns, there arebasically three types of flow in symmetrical geometry: mass-flow,funnel-flow and expanded flow. Pertaining food systems, funnel-flow bins may be used forgrains, pulses, oilseeds, and so on, mainlyfor the application of feeding directly such materials to processing,such as in cereals extrusion or cereal milling (Ortega-Rivas, 2005).In recent years, most of grains are stored conical bottom silos to

use in future. To obtain and record of emptying time of silos undergravity forces is very important. For this purpose, we obtained vol-umetric and gravimetric flow rate values of carob seed from modelsilos.

Volumetric flow rate values of carob seeds were found higherthan gravimetric flow rate values at all fraction. Both volumetricand gravimetric flow rate decreased, as seed size increased. Thevolumetric flow rates of carob seed were found 120.09, 115.96, and110.05 ml/s and gravimetric flow rates were found 108.74, 105.78,and 99.57 g/s at the small, medium, and large seed size fractions,respectively.

The filling angle of repose values were obtained higher thanemptying angle of repose values in all carob seed fraction. As seedsize increased, both values of filling and emptying angle of repose

decreased. The values of emptying angle of repose of carob seedwere 27.75, 23.96, and 22.41, and the values of filling angle of repose were 33.29, 32.47, and 27.85 at the small, medium, andlarge fraction, respectively. Ogunjimi et al. (2002) f or locust beanseed Akaaimo and Raji (2006) f or africana seed, and Paksoy andAydin (2004) f or edible squash, and Cos kuner and Karababa (2007)for flaxseed reported similar angle of repose values. These resultswere lower than those of karingda (Suthar and Das, 1996), sun-flower seed (Gupta and Das, 1997), and guna seed (Aviara et al.,1999).

Thestaticcoefficient of friction of carob seed was evaluated overfive different surfaces: stainless steel, galvanized iron, polypropy-lene knitted bag, aluminum and PVC. While increasing trends (forstaticcoefficient of friction values) obtained forcarobseed depends

on increasing dimension on the metallic surfaces (stainless steel,

galvanized iron and aluminum) and decreasing static coefficientof friction values obtained on PVC and knitted bag. It is foundthat the static coefficient of friction is lowest against stainlesssteel at all fractions. This may owing to the smoother and pol-ished surface of the stainless steel compared other sheets used.Same results were found previous study (Cos kuner and Karababa,2007). PVC surface had the highest coefficient of friction (0.532)at the small fraction followed by knitted bag (0.504), galvanizediron (0.389), aluminum (0.349), and stainless steel (0.344). On theother hand, at the large fraction, galvanized iron (0.482) had thehighest coefficient of friction followed by, PVC (0.472), knitted bag(0.466), aluminum (0.409), and stainless steel (0384), respectively.Thecoefficient of friction forcarobseed washigherthan that of kar-ingdaseed(SutharandDas,1996), quinoaseeds(Vilcheetal.,2003),andediblesquash (Paksoyand Aydin,2004) against galvanized ironsheet.Ontheotherhand,carobseedsshowedthatlowerstaticcoef-ficient of friction to that of sunflower seeds (Gupta and Das, 1997),sesameseed (Tunde-Akintunde and Akintunde, 2004), and flaxseed(Cos kuner and Karababa, 2007) against both galvanized iron andstainless steel sheet, and flaxseed (Cos kuner and Karababa, 2007)against aluminum sheet and polypropylene knitted bag.

4. Conclusion

Thefollowing conclusions arerevealed from the investigation of some physical properties of carob bean (C. siliqua L.) at average of 13.8% (d.b.) moisture content. The frequency distribution curves of the axial dimensions tend a nearly normal distribution. The aver-age seed length, width, thickness and geometric mean diameterwere 8.69mm, 6.43mm, 3.88 mm, and 5.99mm, respectively. Theaverage 1000 seed weight, volume and surface area of carob beanwere 158.56g, 81.23 mm3 and 96.22mm2, while the sphericity andaspect ratio were 0.70 and 74.09%, respectively. Shape indices of ungraded carob beans depends on their perpendicular dimensionswere classified in bladed (72%) and compact-bladed (20%). Theaverage bulk density of seed was 0899kg/m3 while the true den-sity was 1364kg/m3, and the corresponding porosity was 33.78%.The average gravimetric and volumetric flow rates of carob beanswere 104g/s and 115.37ml/s, respectively. The average filling andemptying angle of repose values were found 31.20◦ and 23.80◦,respectively. Thestaticcoefficient of friction on five different mate-rials has been found out and the results showed that the meanvalue of static coefficient friction was least in case of stainless steelsheet while it is highest for PVC. In summary, this paper dealswith the physical properties of industrial gum producing crop of carob beans, providing useful data for its postharvest handling andindustrial processing.

Acknowledgement

Authors thank to Incom A.S . (Mersin, Turkey) for the supplyingof raw carob beans.

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