M

Ra

b

a

A

R

R

A

K

J

P

M

1

Ibwmrcg(fuc1i(

0d

i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 341–347

avai lab le at www.sc iencedi rec t .com

journa l homepage: www.e lsev ier .com/ locate / indcrop

oisture-dependent physical properties of jatropha fruit

.C. Pradhana, S.N. Naika,∗, N. Bhatnagarb, V.K. Vijaya

Centre for Rural Development & Technology, Indian Institute of Technology, Hauz Khas, New Delhi 110016, IndiaMechanical Engineering Department, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India

r t i c l e i n f o

rticle history:

eceived 9 April 2008

eceived in revised form 2 July 2008

ccepted 2 July 2008

eywords:

atropha fruit

hysical properties

oisture content

a b s t r a c t

The physical properties of fruit are important in designing and fabricating equipment and

structures for handling, transporting, processing and storage, and also for assessing quality.

The study was conducted to investigate some physical properties of jatropha fruit at var-

ious moisture levels. The average length, width, thickness and 1000 mass were 29.31 mm,

22.18 mm, 21.36 mm and 1522.10 g, respectively, at moisture content of 7.97% d.b. The geo-

metric mean diameter increased from 24.03 to 24.70 mm and the sphericity varied between

0.82 and 0.83 as moisture content increased from 7.97% to 23.33% d.b., respectively. In the

same moisture range, the bulk and true densities decreased from 278 to 253 and 546 to

435 kg m−3, respectively, whereas the corresponding porosity also decreased from 49.08% to

41.84%. As the moisture content increased from 7.97% to 23.33% d.b., crushing strength was

decreased from 275 to 79 N, whereas the angle of repose and surface areas were found to

increase from 36.41◦ to 41.72◦ and 1815.73 to 1917.59 mm2, respectively. The static coefficient

of friction of jatropha fruit increased linearly against the surfaces of three structural mate-

rials, namely plywood (47.81%), mild steel (62.88%) and aluminium (34.82%) as the moisture

content increased from 7.97% to 23.33% d.b.

In India jatropha bears fruit between September and Decem-

. Introduction

n the present scenario, when most of the cultivable area haseen occupied by conventional/cultivated crops, plant specieshich can grow in wastelands under less favourable environ-ental conditions need to be promoted (NOVOD, 1995). In this

egard, jatropha has been widely accepted as a potential agri-ultural solution for subtropical and tropical locations andrown for large-scale cultivation for production of biodieselBiofuel Report, 2003). The growth in energy demand in allorms is expected to continue unabated owing to increasingrbanization, standard of living and population. In the Indianontext, the estimated import of crude oil may go up from 85 to

47 MMT per annum by the end of 2006–2007, correspondinglyncreasing the import bill from $13.3 billion to $15.7 billionBiofuel Report, 2003).

∗ Corresponding author. Tel.: +91 11 26591162; fax: +91 11 26591121.E-mail address: sn naik@hotmail.com (S.N. Naik).

926-6690/$ – see front matter © 2008 Elsevier B.V. All rights reserved.oi:10.1016/j.indcrop.2008.07.002

© 2008 Elsevier B.V. All rights reserved.

Jatropha (Jatropha curcas L.), is native to South America andhas a long history of propagation by Portuguese in Africa andAsia (Bringi, 1987). In unkept hedges, jatropha yields around4 tonnes of seed ha−1 (Henning, 1998), while under optimalconditions (depending upon local growing conditions, such aswater, nutrient availability and the absence of pests and dis-eases) maximum yields of up to 8 tonnes of seed ha−1 can beachieved. It is well adapted to arid and semi-arid conditionsand often used for erosion control (Heller, 1996). The produc-tive lifespan of jatropha can be 50 years. Jatropha will startto produce fruit after 6 months and the productivity will bestable after the plant is 1–3 years old (Manurung et al., 2006).

ber. Unlike most other trees fruiting in the monsoons with allthe attendant difficulties of collection, drying and storage, jat-ropha offers a natural advantage and the fruit can be collected

r o d

342 i n d u s t r i a l c r o p s a n d p

during the dry season (Bringi, 1987). The fruit dries and the hullor shell becomes hard and black. The dry fruits remain on thebranches and contain 2–3 seeds. The fruits are hand pickedor harvested by hitting the fruits with a long stick. At times,older trees are harvested by shaking the tree/branches. Thecollected fruits are sun dried for processing and decorticatedmanually to get the seeds (Lakshmikanthan, 1978).

In the process of extracting jatropha seed oil and its deriva-tives, the fruits undergo a series of unit operations. Thephysical properties of jatropha fruit are essential to designequipment for harvesting, drying, cleaning, grading, decorti-cation and storage. The physical properties of jatropha fruitdepend on its moisture content, and this knowledge is essen-tial for the design of harvest and post harvest equipment(e.g., mechanical harvesters, driers, graders, decorticators,and storage bins) (Sahay and Singh, 1996).

Review of the literature has revealed that research hasbeen conducted on jatropha seeds and its oil for prepara-tion of biodiesel, and detoxification experiments with thejatropha seed oil (Haas and Mittelbach, 2000; Shah et al.,2004; Berchmans and Hirata, 2008; Garnayak et al., 2008).However, detailed measurements of the principal dimensionsand the variation of physical properties of jatropha fruitsat various levels of moisture content have not been inves-tigated. The purpose of this study is to determine somemoisture-dependent, physical properties of jatropha fruit: lin-ear dimensions, size, sphericity, surface area, 1000 fruits mass,bulk density, true density, porosity, angle of repose, crushingstrength and static coefficient of friction in the moisture rangeof 7.97–23.33% d.b.

2. Materials and methods

Mature (black colour) jatropha fruits were hand picked fromthe trees and gathered together from Haryana (Bawel), India.The cleaned and graded fruits were sun dried for 2 daysbefore beginning the study and the initial moisture contentof the fruit was determined by using the standard hot air ovenmethod at 105 ± 1 ◦C for 24 h (Brusewitz, 1975; Gupta and Das,1997; Özarslan, 2002; Altuntas et al., 2005; Coskun et al., 2005).The initial moisture content of the fruits was 7.97% d.b.

Samples were moistened with a calculated quantity ofwater by using the following Eq. (1) (Coskun et al., 2005),and conditioned to raise their moisture content to the sevendesired levels:

Q = Wi(Mf − Mi)100 − Mf

(1)

where Q is the mass of water added (kg); Wi is the initial massof the sample (kg); Mi is the initial moisture content of thesample (%, d.b.); and Mf is the final moisture content of thesample (%, d.b.).

The samples were placed in high molecular high den-sity polyethylene bags of 100 �m thickness and the bagssealed tightly. The samples were kept at 5 ◦C in a refrigera-

tor for a week to enable the moisture to distribute uniformlythroughout the sample. Before starting the tests, the requiredquantities of the samples were taken out of the refrigeratorand allowed to warm up to room temperature for about 2 h.

u c t s 2 9 ( 2 0 0 9 ) 341–347

All the physical properties of the fruit were assessed at mois-ture levels of 7.97%, 10.53%, 13.09%, 15.65%, 18.21%, 20.77%and 23.33% d.b. This rewetting technique to attain the desiredmoisture content in seed and grain has frequently been used(Nimkar and Chattopadhyay, 2001; Sacilik et al., 2003; Coskunet al., 2005). For each moisture content, the length, width andthickness of the fruit were measured by a vernier caliper (Mitu-toyo, Japan) with an accuracy of 0.02 mm.

The average diameter of fruit is calculated by using thearithmetic mean and geometric mean of the three axialdimensions. The arithmetic mean diameter, Da, and geomet-ric mean diameter, Dg, of the fruit were calculated by usingthe following relationships (Mohsenin, 1970):

Da = L + W + T

3(2)

Dg = (LWT)1/3 (3)

The sphericity, �, of jatropha fruit was calculated by usingthe following relationship (Mohsenin, 1970):

� = (LWT)1/3

L(4)

where L is the length, W is the width and T is the thickness,all in mm.

One thousand fruit mass was determined by means ofa digital electronic balance (Shimadzu Corporation Japan,AY120) having an accuracy of 0.001 g. To evaluate the 1000 fruitmass, 30 randomly selected fruits from each moisture levelwere averaged.

The surface area of jatropha fruit was found by analogywith a sphere of the same geometric mean diameter, usingthe following equation (Sacilik et al., 2003; Tunde-Akintundeand Akintunde, 2004; Altuntas et al., 2005):

S = �D2g (5)

where S is the surface area (mm2).The bulk density was determined by filling a cylindrical

container of 500 ml volume with the fruit from a height of150 mm at a constant rate and then weighing the contentsby means of a digital electronic balance (Shimadzu Corpora-tion Japan, AY120) having an accuracy of 0.001 g (Gupta andDas, 1997). No separate manual compaction of fruits was done.The bulk density was calculated from the mass of the fruitsand the volume of the container. The true density as functionof moisture content was determined using the toluene (C7H8)displacement method in order to avoid absorption of waterduring the experiment (Jha, 1999; Coskuner and Karababa,2007). Toluene was used instead of water because of its lowabsorption by the fruits, its surface tension is low, so that itfills even shallow dips in fruit, and its dissolution number islow (Mohsenin, 1970). The fruits were used to displace toluenein a measuring cylinder after their masses had been measured

(digital electronic balance having an accuracy of 0.001 g, Shi-madzu Corporation Japan, AY120). The true density was foundas an average of the ratio of their masses to the volume oftoluene displaced by the fruits.

d u c

oa(

ε

w�

rTamocaccmpf

�

wcaS

aspcdwpt

dawpfiTTgcrTr

�

wi

de

i n d u s t r i a l c r o p s a n d p r o

The porosity, ε, in % is the parameter indicating the amountf pores in the bulk materials. It is calculated from bulknd true densities using the relationship given as followsMohsenin, 1970):

=(

1 − �b

�t

)100 (6)

here ε is the porosity (%); �b is the bulk density (kg m−3); and

t is the true density (kg m−3).The angle of repose is the characteristic of the bulk mate-

ial which indicates the cohesion among the individual fruits.he higher the cohesion, the higher the angle of repose. Thengle of repose is the angle from the horizontal at which theaterial will rest in a pile. This was determined by using an

pen-ended cylinder of 15 cm diameter and 50 cm height. Theylinder was placed at the centre of a circular plate havingdiameter of 70 cm and was filled with jatropha fruit. The

ylinder was raised slowly until it formed a cone on the cir-ular plate. The height of the cone was recorded by using aoveable pointer fixed on a stand having a scale of 0–1 cm

recision. The angle of repose, �, was calculated using theormula:

= tan−1(

2H

D

)(7)

here H is the height of the cone (cm), and D is the diameter ofone (cm). Other researchers have used this method (Fraser etl., 1978; Joshi et al., 1993; Kaleemullah and Gunasekar, 2002;acilik et al., 2003; Karababa, 2006).

Crushing strength of jatropha fruits was measured usingInstron-5582 test instrument. The fruit was placed on the

tationary lower platform along its natural rest position andressed with the moving platform for the various moistureontents. The probe used in the experiment had a 20 mmiameter and was connected to a computer. The experimentas conducted at a loading velocity at 2 mm min−1. The com-ressive force corresponding to the crushing of the fruit wasaken as the crushing strength of the fruit.

The static coefficient of friction, �, of jatropha fruit wasetermined on three different materials, plywood, aluminiumnd mild steel sheet. A tilting platform of 350 mm × 120 mmas fabricated and used for experimentation. An open-endedlastic cylinder having 65 mm diameter and 40 mm height waslled with the fruit and placed on the adjustable tilting surface.he box was raised slightly so as not to touch the surface.he structural surface with the box resting on it was inclinedradually with a screw device (screw pitch 1.4 mm), until theylinder just started to slide down and the angle of tilt wasead (Fraser et al., 1978; Dutta et al., 1988; Nimkar et al., 2005).he coefficient of friction was calculated from the followingelationship:

= tan˛ (8)

here � is the coefficient of friction and ˛ is the angle of tilt

n degrees.

One-hundred jatropha fruits were randomly chosen toetermine the average size (length, width and thickness) atach moisture level from 7.97% to 23.33% d.b. Ten replications

t s 2 9 ( 2 0 0 9 ) 341–347 343

at each moisture content were taken to determine the otherphysical properties of the fruits. The results obtained weresubjected to analysis of variance (ANOVA) and DUNCAN testusing SPSS 10.0 software and analysis of regression has beenusing Microsoft excel.

3. Results and discussion

3.1. Fruit dimensions

Average values of the three principal dimensions of jat-ropha fruit, length, width and thickness determined in thisstudy at different moisture contents are presented in Table 1.Each principal dimension appeared to be linearly depen-dent on the moisture content. It was observed between thethree principal dimensions and moisture content that uponmoisture absorption, the jatropha fruit expands in length,width and thickness within the moisture range of 7.97% to23.33% d.b. The mean dimensions of 100 fruits measured ata moisture content of 7.97% d.b. are: length 29.31 ± 0.30 mm,width 22.18 ± 0.30 mm and thickness 21.36 ± 0.46 mm. Themean dimensions show an increase of 2.02%, 2.95% and3.34% in length, width and thickness, respectively, due toa change in moisture level from 7.97% to 23.33% d.b. Dif-ferences between the values were statistically significant atP < 0.05.

The average diameter calculated by the arithmetic meanand geometric mean is also presented in Table 1. The averagediameters increased with the increase in moisture content asaxial dimensions. The arithmetic and geometric mean diam-eter range changed from 24.28 to 24.94 and 24.03 to 24.70 mmas the moisture content increased from 7.97% to 23.33% d.b.,respectively (P < 0.05). The length, breadth, thickness, arith-metic mean diameter and geometric mean diameter areimportant in designing of separating, harvesting, sizing andgrinding machines (Sahay and Singh, 1996).

3.2. Sphericity

The product shape can be determined in terms of its spheric-ity which affects the flow ability characteristics. The values ofsphericity were calculated individually (Eq. (4)) by using thedata on geometric mean diameter and the major axis of thefruit and the results obtained are presented in Table 1. Thesphericity of fruits calculated at different moisture contentsexhibited a change from 0.82 to 0.83, indicating that spheric-ity of jatropha fruit is not significantly (P < 0.05) affected bythe change in moisture content from 7.97% to 23.33% d.b.Sirisomboon et al. (2007) have reported the value of sphericityas 0.95, which is higher than the result of this investiga-tion. However, increase in the sphericity with increase inmoisture content was observed for arecanut (Areca catechuL.) kernel (Kaleemullah and Gunasekar, 2002) and fenu-greek (Trigonella foenum-graceum L.) seeds (Altuntas et al.,2005).

The grain is considered spherical when the sphericity valueis more than 0.80 and 0.70 (Bal and Mishra, 1988; Dutta etal., 1988). In the present study, jatropha fruit is treated as anequivalent sphere for calculation of the surface area.

344 i n d u s t r i a l c r o p s a n d p r o d

Tabl

e1

–Ph

ysic

alp

rop

erti

esof

jatr

oph

afr

uit

atd

iffe

ren

tm

oist

ure

con

ten

t

Moi

stu

reco

nte

nt

(%,d

.b.)

Axi

ald

imen

sion

s(m

m)

Ave

rage

dia

met

ers

(mm

)Sp

her

icit

y(d

ecim

al)

Surf

ace

area

(mm

2)

Bu

lkd

ensi

ty(k

g/m

3)

Tru

ed

ensi

ty(k

g/m

3)

Poro

sity

(%)

An

gle

ofre

pos

e(◦ )

1000

Fru

itm

ass

(g)

Len

gth

,LW

idth

,WT

hic

knes

s,T

Ari

thm

etic

mea

n,D

a

Geo

met

ric

mea

n,D

g

7.97

29.3

1a(0

.30)

22.1

8a(0

.30)

21.3

6a(0

.46)

24.2

8a(0

.24)

24.0

3a(0

.51)

0.82

a(0

.01)

1815

.73a

(38.

26)

278a

(3.1

4)54

6a(2

.18)

49.0

8a(0

.32)

36.4

1a(3

.20)

1522

.10a

(10.

07)

10.5

329

.37b

(0.8

7)22

.22a

(0.6

2)21

.61b

(0.6

5)24

.40a

(0.5

2)24

.16b

(0.2

5)0.

82a

(0.0

2)18

34.4

0b(7

7.73

)27

5b(1

.79)

520a

(6.4

8)47

.11a

(0.1

1)36

.86bc

(4.6

3)16

70.3

5b(1

3.26

)13

.09

29.4

4bc(0

.51)

22.4

6b(0

.60)

21.6

1c(0

.52)

24.5

0b(0

.71)

24.2

7b(0

.67)

0.82

a(0

.02)

1850

.83c

(44.

62)

273b

(3.2

8)49

8ab(5

.24)

45.1

8ab(0

.43)

37.7

7cd(6

.12)

1734

.15c

(10.

87)

15.6

529

.62cd

(0.3

8)22

.56c

(0.6

2)21

.81cd

(0.6

7)24

.66bc

(0.2

7)24

.43bc

(0.6

8)0.

82a

(0.1

3)18

75.3

2d(8

0.22

)26

7c(4

.21)

470c

(7.8

8)43

.19c

(0.3

6)38

.67d

(5.7

7)17

74.4

5d(1

5.01

)18

.21

29.7

2d(0

.76)

22.5

8cd(0

.75)

21.8

8d(0

.69)

24.7

2c(0

.53)

24.4

8c(0

.72)

0.82

ab(0

.05)

1884

.35e

(77.

23)

261cd

(3.6

7)45

9d(4

.26)

43.1

4d(0

.34)

39.5

3e(4

.28)

1805

.11e

(13.

91)

20.7

729

.80e

(0.5

1)22

.80d

(0.8

6)21

.89e

(0.6

8)24

.83cd

(0.6

6)24

.60d

(0.6

8)0.

82b

(0.0

8)19

01.4

6ef(4

6.03

)25

5d(2

.03)

440e

(3.4

0)42

.04e

(0.2

2)40

.63e

(2.0

3)18

48.0

1f(1

2.58

)23

.33

29.9

0f(0

.82)

22.8

3e(0

.37)

22.0

7f(0

.40)

24.9

4d(0

.52)

24.7

0e(0

.49)

0.83

c(0

.034

)19

17.5

9f(7

5.19

)25

3e(3

.57)

435f

(1.5

9)41

.84e

(0.1

1)41

.72f

(3.5

6)18

84.0

6f(1

6.26

)

Figu

res

inp

aren

thes

isar

est

and

ard

dev

iati

on.V

alu

esin

the

sam

eco

lum

ns

foll

owed

byd

iffe

ren

tsu

per

scri

pt

lett

ers

(a–f

)are

sign

ifica

nt

dif

fere

nt

(P<

0.05

).

u c t s 2 9 ( 2 0 0 9 ) 341–347

3.3. Thousand fruit mass

The mass of 1000 jatropha fruits, M1000, in g increases from1522.10 to 1884.06 g (P < 0.05) as the moisture content, M,increases from 7.97% to 23.33% d.b. (Table 1). The linear equa-tion for 1000 fruit mass can be formulated as:

M1000 = 1418.2 + 21.09M

with a value for the coefficient of determination R2 of 0.91.Similar trends have been reported for neem (Azadirachta

indica L.) nut, cotton (Gossypium hisutum L.) seed, hemp seed(Cannabis sativa L.), monogerm sugarbeet (Beta vulgaris var.altissima) seed and faba bean (Vicia faba L.) grains (Visvanathanet al., 1996; Özarslan, 2002; Sacilik et al., 2003; Kasap andAltuntas, 2006; Altuntas and Demirtola, 2007; Altuntas andYıldız, 2007).

3.4. Surface area

The surface area, S, of the fruit is calculated by using Eq. (5). Asseen from Table 1, the surface area of jatropha fruit increaseslinearly from 1815.73 to 1917.59 mm2 (statistically significantat P < 0.05), when the moisture content increases from 7.97%to 23.33% d.b. A similar trend has been reported for linseed(Linum usitatissimum L.) and red kidney bean (Phaseolus vulgarisL.) grains (Selvi et al., 2006; Isik and Ünal, 2007). The variationof moisture content, M, and surface area, S, can be expressedmathematically as follows:

S = 1765.2 + 6.60M

with a value for R2 of 0.99.

3.5. Bulk density

The fruit bulk density at different moisture levels varied from278 to 253 kg m−3 (P < 0.05) as shown in Table 1 and indicated adecrease in bulk density with an increase in moisture con-tent with significant variation. This is due to the fact thatmass increased owing to moisture gain in the fruit sample,subsequently decreasing the bulk density. The negative lin-ear relationship of bulk density with moisture content is alsoobserved by various other researchers (Dutta et al., 1988; Guptaand Prakash, 1990; Carman, 1996). A similar decreasing trendin bulk density has been reported for neem nut by Visvanathanet al. (1996). The bulk density, �b, of fruit is found to have thefollowing linear relationship with moisture content, M:

�b = 293.7 − 1.77M

with a value for R2 of 0.98.

3.6. True density

The true density of the fruit was measured at different mois-ture levels and was found to be negatively correlated andvaries from 546 to 435 kg m−3 (Table 1). The decrease (P < 0.05)

in true density value with increase in moisture content, M,might be attributed to the relatively higher true volume ascompared to the corresponding mass of the fruit attained dueto the adsorption of water. The results are in conformity with

d u c t s 2 9 ( 2 0 0 9 ) 341–347 345

waml

�

w

3

PaotfirVkisf

ε

w

3

Tflrumrofta�

m

�

w

3

Tecinihse

C

w

i n d u s t r i a l c r o p s a n d p r o

ork reported for soybean (Glycine max L.) and gram (Cicerrietinum L.) (Dutta et al., 1988; Deshpande et al., 1993). Theoisture dependence of the true density, �t, is described by a

inear equation as follows:

t = 597.3 − 7.42M

ith a value for R2 of 0.97.

.7. Porosity

orosity was evaluated using the mean values of bulk densitynd true density in Eq. (6). The variation of porosity dependsn moisture content as shown in Table 1. The porosity is foundo decrease linearly from 49.08% to 41.84% (P < 0.05) in speci-ed moisture levels. Although the results are similar to thoseeported for soybean and neem nut (Deshpande et al., 1993;isvanathan et al., 1996), a different trend is reported for redidney bean grains by Isik and Ünal (2007). The porosity value

s often needed in air flow and heat flow studies. The relation-hip between porosity, ε, and the moisture content, M, of theruit is obtained as:

= 51.92 − 4.73 × 10−1M

ith a value for R2 of 0.91.

.8. Angle of repose

he angle of repose is an indicator of the product’s ability toow. The experimental results for the angle of repose withespect to moisture content are shown in Table 1. The val-es are found to increase from 36.41◦ to 41.72◦ (P < 0.05) in theoisture range of 7.97–23.33% d.b. This variation of angle of

epose with moisture content occurs because the surface layerf moisture surrounding the particle holds the aggregate ofruits together by the surface tension. These results are similaro those reported for neem nut and hemp seed (Visvanathan etl., 1996; Sacilik et al., 2003). The value of the angle of repose,, for jatropha fruit bears the following relationship with itsoisture content, M:

= 33.29 + 3.52 × 10−1M

ith a value for R2 of 0.98.

.9. Crushing strength

he crushing strength of the jatropha fruit decreased lin-arly from 275 to 79 N (P < 0.05) with the increase in moistureontent in the range of 7.97–23.33% d.b. A similar decreas-ng trend in crushing strength has been reported for neemut (Visvanathan et al., 1996). The decrease in the crush-

ng strength may be owing to the fruit becoming softer atigher moisture contents. The relationship between crushingtrength, Cs, and the moisture content, M, of the fruit can be

xpressed mathematically as follows:

s = 384.24 − 12.16M

ith a value for R2 of 0.97.

Fig. 1 – Effect of moisture content on static coefficient offriction of jatropha fruit against various surfaces.

3.10. Static coefficient of friction

The static coefficient of friction of jatropha fruit on threesurfaces (plywood, aluminum and mild steel sheet) againstmoisture content in the range of 7.97–23.33% d.b. are shownin Fig. 1. It is observed that the static coefficient of frictionincreased linearly with increase in moisture content for allcontact surfaces. The reason for the increased friction coeffi-cient at higher moisture content may be owing to the waterpresent in the fruit offering a cohesive force on the surface ofcontact. An increase of 47.81%, 62.88% and 34.81% are recordedin the case of plywood, mild steel and aluminum, respectively,as the moisture content increases from 7.97% to 23.33% d.b. Atall moisture contents, the maximum friction is offered by ply-wood, followed by the mild steel and aluminium surfaces. Theleast static coefficient of friction may be owing to the smootherand more polished surface of the aluminium sheet than theother materials used. Plywood also offered the maximum fric-tion for gram, rape (Brassica napus L.) seed and neem nut andthe coefficient of friction increases with the moisture content(Dutta et al., 1988; Kulkelko et al., 1988; Visvanathan et al.,1996). The relationships between static coefficient of friction,�, and moisture contents, M, on plywood (wd), aluminium(al) and mild steel (ms) can be represented by the followingequations:

�wd = 0.43 + 0.02M (R2 = 0.97)�al = 0.34 + 0.01M (R2 = 0.94)�ms = 0.33 + 0.02M (R2 = 0.98)

4. Conclusions

The following conclusions are drawn from the investigationon moisture-dependent physical properties of jatropha fruitwith moisture contents ranging from 7.97% to 23.33% d.b. Asmoisture content increases from 7.97% to 23.33% d.b., the aver-age length, width, and thickness of jatropha fruit changes

from 29.31 to 29.90, 22.18 to 22.83 and 21.36 to 22.07 mm,respectively. One thousand fruit mass and surface area of jat-ropha fruit varied from 1522.10 to 1884.06 g and 1815.73 to1917.59 mm2, respectively, within the specific moisture con-

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tents. The geometric mean diameter and sphericity are foundto increased from 24.03 to 24.70 mm and 0.82 to 0.83, respec-tively, in the moisture range of 7.97–23.33% d.b. The bulkdensity and true density decreased from 278 to 253 and 546to 435 kg m−3, respectively, while the porosity is decreasedfrom 49.08% to 41.84% as the moisture content increasedfrom 7.97% to 23.33% d.b. The angle of repose increasedfrom 36.41◦ to 41.72◦ as the moisture content increased from7.97% to 23.33% d.b. The crushing strength of jatropha fruitdecreased from 275 to 79 N in the specified level of moisturecontents.

The static coefficient of friction increased for all threesurfaces, namely, plywood (0.62–0.91, 47.81%), mild steel(0.46–0.75, 62.88%) and aluminium (0.45–0.60, 34.82%) as themoisture content increased from of 7.97% to 23.33% d.b. Thedifferences between all the values are statistically significantat P < 0.05.

Acknowledgements

Funding for this research was provided by the National Oilseedand Vegetable oils Development (NOVOD) Board, Governmentof India, Gurgaon, Delhi. The authors are grateful to Dr. A.P.Sivastava, Principal scientist, Indian Agricultural ResearchInstitute, New Delhi, for providing facilities in their labora-tory.

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