Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2013
Volume 16
Issue 4
Topic:
Agricultural Engineering
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Salawu A. , Suleiman M. , Isiaka M. 2013. PHYSICAL PROPERTIES OF JATROPHA CURCAS SEED, EJPAU 16(4), #07.
Available Online: http://www.ejpau.media.pl/volume16/issue4/art-07.html

PHYSICAL PROPERTIES OF JATROPHA CURCAS SEED

A.T. Salawu1, M.L. Suleiman2, M. Isiaka2
1 No. 5 Augustine O. Salawu Street, Worgor Area, Ejigbo. Osun State. Nigeria
Department of Agricultural Engineering, Ahmadu Bello University, Zaria, Nigeria
2 Department of Agricultural Engineering, Ahmadu Bello University, Zaria, Nigeria

 

ABSTRACT

This study was conducted to investigate the physical properties of Jatropha curcas seed (JCS) found in North West Ecological Zone of Nigeria. The seed length, width, thickness, geometric mean diameter, sphericity, one thousand seed weight, surface area, unit volume, bulk volume, true density, bulk density, specific surface area, porosity, static angle of repose and coefficient of static friction were the parameters investigated at 7.5% moisture content dry basis. The obtained results range from 15.13–18.89 mm, 10.02–11.95 mm, 5.58–9.20 mm and 10.46–12.62 mm for length, width, thickness and geometric mean diameter, respectively. The unit volume, bulk volume, one thousand seed weight, true density, bulk density and porosity were found to be in the range of 79.00–85.00 cm3, 138.00–153.00 cm3, 535.30–611.90 g, 0.67–0.73 g cm-3, 0.37–0.42 g cm-3 and 38.41–45.70%, respectively. Sphericity, surface area, specific surface area and static angle of repose investigated were in the range of 56.15–72.37%, 3.44–5.01 cm2, 4.88–5.49 cm2 cm-3, and 23.03–28.66°, respectively. The coefficient of static friction against the surfaces examined was in the range of 0.235–0.244, 0.415–0.455, 0.450–0.465 and 0.361–0.375 for steel sheet, ply wood, rubber and aluminium, respectively. The properties will provide a data base for designing equipment for production, handling, processing and storage of the seeds.

Key words: Jatropha curcas seed, physical properties.

INTRODUCTION

Jatropha curcas isa native of tropical America and has been grown throughout tropical and subtropical parts of Asia and Africa. Jatropha comes from the Greek words jatrós meaning medical and trophé meaning food [12]. It is variously known as physic nut, pinonillo, black vomit nut, purging nut (Barbados), and big purge nut. It is mostly planted as living fence to prevent animals from entering and destroying farm crops. It is a drought resistance plant that can grow into large shrub with thick branches and numerous large leaves attaining a height of 3–4 m in 3 years. The plants can be propagated through the seed or via stem cutting.

Fruits are drupe ovoid capsules, 1.5 to 3.0 cm in diameter. They start fleshy, but become dehiscent when dry [12]. The fruit development is about 90 days from flowering to seed maturity. The fruit encapsulate three seeds with a seed in each cavity and split into three parts at maturity. It is initially green, changing to yellow, then brown, and finally black when it reaches maturity [12]. Various researchers have reported the oil content per weight of JCS; Gubitz et al. [17] and Forson et al. [13] reported an oil content of 35–40% and 30–38%, respectively; while GANBC [14], Haque et al.[18], Global Floral Biotech [16], Vishnu and Kalpak [34] reported 37, 32.4, 35 and 33%, respectively.

This wonder plant has been one of the focal areas of research and development as a substitute to depleting fossil fuel. It is a non-edible oil crop that can be grown under a wide range of soils and climate conditions. Though some researchers [31, 15, 23] have documented physical properties of JCS, none of them were reported for JCS cultivated or found in North West Ecological Zone of Nigeria.

With a view to encourage green fuel (biofuel) and to reduce dependence on fossil fuel, Legumes and Oil Seeds Research Programme, Institute for Agricultural Research, Ahmadu Bello University Zaria, Nigeria is putting in more inputs to cultivate JCS. At present, production, handling and processing of this crop are being done manually. These operations are energy sapping, time consuming, less efficient and low output per unit time. In order to mechanize its production, handling, processing and storage, precise knowledge of its physical properties should be obtained. Given the economic importance of JCS as a source of an outstanding biofuel that can substitute fossil fuel, there is a need to investigate the design related physical properties of this seeds. The knowledge of physical properties of agricultural products is very essential for the design of suitable machines and equipment for the production, handling, processing and storage of these products [19].

Axial dimension of the materials are useful in sizing, sorting and other separation process design. It is of paramount importance in determining the aperture size of the shelling machine screen. The seeds axial dimensions are required in the design of planter. Its knowledge is required in the design of conveyance auger in the screw press oil extraction machine. Optimization of the screw press pitch and the clearance of the screw from the press barrel also depend on the seed axial dimension. Precise knowledge of bulk and true densities of seeds are important in the designing of equipment for its processing, sorting, grading, transporting and storing. Bulk and true densities of seeds are important parameters in determining the storage capacity. The porosity of seed is important because it shows the resistance of the seeds to airflow during drying process [1]. Knowledge of JCS porosity is required in the design of forced-air drier, and the energy optimization of drying process. Surface area and specific surface area affect the resistance to air flow via the bulk material bed and are also important factors to be considered in drying process. Sphericity of the seed determines its ability either to slide on their flat surfaces or to roll. This parameter is of utmost importance in designing of hopper to handle the seeds [1]. The angle of repose is important for designing package or storage structures [19]. It is also useful in determining angle of tilt for machine’s hopper. The coefficient of static friction against different structural surfaces is of paramount importance in determining the steepness of the storage container, hopper or any other loading and unloading device [10]. It gives an indication of the amount of power required to convey the materials against different structural surfaces. The objective of this study is to determine the design related physical properties of JCS found in North West Ecological Zone of Nigeria. These parameters will be useful in designing equipment for production, handling, processing and storage of the JCS.

MATERIALS AND METHODS

Sample Preparation

JCS were obtained from Legumes and Oil Seeds Research Programme, Institute for Agricultural Research, Ahmadu Bello University Zaria, Nigeria. Zaria is within the North West Ecological Zone of Nigeria. Prior to determination of its physical properties, the dirt, foreign materials, bad seeds and immature seeds were removed in other to get good seeds (Fig. 1).

Fig. 1. Jatropha curcas seeds

The initial moisture content of the seeds on dry basis was determined by oven drying at 105°C for 24 hours using the relationship given by Haque et al. [18]:

(1)

Where MCdb = Moisture content on dry basis [% db]
M1 = Weight of wet sample [g]
M2 = Weight of bone dry matter [g]

Ten replications were made and the average moisture content of JCS was found to be 7.5% dry basis. At this moisture content, the physical properties of JCS were determined at Processing Laboratory of Agricultural Engineering Department, Ahmadu Bello University Zaria, Nigeria.

Experimental Procedures
Physical properties of JCS that were determined include length, width, thickness, geometric mean diameter, sphericity, one thousand seed weight, surface area, unit volume, bulk volume, true density, bulk density, specific surface area, porosity, static angle of repose and coefficient of static friction. The methods used to determine the physical properties of JCS are as outlined below.

Size and Shape: One hundred seeds were randomly selected for size and shape determination. The axial dimensions in terms of length (L); width (W) and thickness (T) were measured with a vernier caliper manufactured by Mitutoyo Corporation, Japan, to an accuracy of 0.01 mm. The geometric mean diameter and shape in term of sphericity were determined using relationship given by Mohsenin [26]:

(2)

(3)

Where Dg = Geometric mean diameter [mm]
S = Sphericity    [%]

Unit volume, Bulk volume, Weight, Density and Porosity
Unit volume was determined using fluid displacement technique. Toluene displacement method in calibrated cylinder was used. The volume of toluene displaced by the seeds (100 seeds) was recorded as volume of the seeds. The bulk volume for 100 seeds was determined by filling an empty 250 ml graduated cylinder with the seed [26]. To achieve uniformity in bulk volume, the graduated cylinder was tapped 10 times for the seeds to consolidate. The volume occupied was recorded as the bulk volume.

A digital weighing balance (Mettler Instrumente AG model P1210, Switzerland) with accuracy of 0.01 g was used to measure one thousand seed weight. This was determined by taken 100 seeds randomly and weighed them; the weight of 100 seeds was multiplied by 10 to have 1000 seeds weight [27, 31]. The procedure was replicated ten times; the average value was obtained and recorded as mean.

In the case of true and bulk densities, the relationships given by Mohsenin [26] were used.
(4)

(5)

Where ρt = True or solid density [g cm-3]
M = Mass of seed [g]
Vu = Unit volume of seed [cm3]
ρb = Bulk density [g cm-3]
Vb = Bulk volume of seed [cm3]

Porosity (P) was determined according to relationship given by Mohsenin [26]
(6)

Surface area and Specific surface area: The surface area was determined using the relationship given by McCabe et al. [24]; Altuntas et al. [2]; and by Dash et al. [9].

(7)

Where A = Surface area [cm2]

The specific surface area was determined using relationship given by Mohsenin [26]:

(8)

Where As = Specific surface area  [cm2 cm-3]

Static angle of repose and Coefficient of static friction: The static angle of repose was determined using the procedure described by Mohsenin [26]; and Garnayak et al. [15]. A hollow bottomless cylinder (50 mm diameter, 100 mm height) was used and then applying trigonometry rules. The cylinder was placed over a plain surface and JCS were filled in. The cylinder was raised slowly allowing the sample to flow down and form a natural slope. The static angle of repose was calculated from the height and diameter of the pile as:

(9)

Where θs = Static angle of repose [°]
H = Height of pile [mm]
D = Diameter of pile [mm]
Fig. 2. Determination of static angle of repose

The coefficient of static friction of JCS against four different surfaces, namely steel sheet, ply wood, rubber and aluminium was determined. A wooden frame (10 cm × 10 cm × 6 cm) without base and lid was placed over different plain surfaces and filled with seeds. The filled frame was pulled along the surface and the peak force required to start motion was recorded by a fixed spring scale. Coefficient of static friction was determined using relationship given by Bahnasawy [5]:

(10)

Where µ = Coefficient of static friction
FT = Force required to start motion of filled frame [N]
FE = Force required to start motion of empty wooden frame [N]
W = Weight of the seeds [N]

Statistical Analysis: The data obtained were subjected to descriptive statistic such as mean, standard deviation and coefficient of variation.

RESULTS AND DISCUSSION

Table 1 shows the summary of the results for the physical properties of Jatropha curcas seed (JCS) at 7.5% moisture content on dry basis. Judging by acceptance range of coefficient of variation (CV) given as ≤ 14% by Isiaka et al. [20], it can be deduced that the variations that exist in the replication of the experiment are negligible and are within the acceptable level.

Size and Shape
The axial dimensions (length, width, and thickness) of seeds vary in the ranges of 15.13–18.89 mm, 10.02–11.95 mm, and 5.58–9.20 mm, respectively. The values reported by Garnayak et al. [15] were 18.65, 11.34 and 8.9 mm; while Sirisomboon et al. [31] reported 21.02, 11.97, and 9.58 mm for length, width, and thickness, respectively. The values reported by Garnayak et al. [15] were in line with the present findings, while Sirisomboon et al. [31] reported values were above the range. The discrepancy between the present findings and that of Sirisomboon et al. [31] might be due to influence of the environmental conditions, plant treatments, and difference in moisture content of the seeds. The mean value of 1000 mass of 1,322.40 g [31] is high compare to 578.04 g obtained in this study. The influence of environmental conditions, plant treatments, and different moisture content of JCS might be the reason why larger values of axial dimensions were reported by Sirisomboon et al. [31]. The lager values of axial dimension and that of 1000 mass also suggest that the moisture content of JCS used by Sirisomboon et al. [31] is relatively high compared to 7.5% db used in this investigation and 9.0% db used by Karaj and Muller [23]. Although the moisture content of JCS used by Sirisomboon et al. [31] were not reported; 88.95, 34.09, 51.87, and 77.03% (wet basis) were reported for hull, kernel, shell, and the whole fruit, respectively. It is evidence that the moisture content of JCS used by Sirisomboon et al. [31] is high since the seeds were obtained from the whole fruits.

An increase in axial dimensions and seed weight has been linked to increase in moisture content of the seeds by Tavakoli et al. [33] for soybean grains, Javad et al. [22] for corn seeds, Bande et al. [8] for Egusi melon seeds and kernel.

Table 1. Physical properties of Jatropha curcas seed at 7.5% Moisture Content on dry basis
Physical property 
Unit
No of observation
Mean value
Minimum   value
Maximum  value
SD
CV
Length , L
mm
100
17.56
15.13
18.89
0.75
3.20
Width, W
mm
100
10.87
10.02
11.95
0.45
1.86
Thickness, T
mm
100
8.23
5.58
9.20
0.53
3.41
Geometric mean Diameter, Dg
mm
100
11.62
10.46
12.62
0.43
1.59
Sphericity, S
%
100
66.22
56.15
72.37
2.30
7.99
1000mass, M
g
10
578.04
535.30
611.90
7.21
9.00
Surface area, A
cm2
100
4.25
3.44
5.01
0.31
2.26
Unit volume, Vu
cm3
10
82.50
79.00
85.00
2.22
5.97
Bulk volume, Vb
cm3
10
145.90
144.00
148.00
1.37
1.30
True density, ρt
g cm-3
10
0.70
0.67
0.73
0.02
0.06
Bulk density, ρb
g cm-3
10
0.40
0.37
0.42
0.02
0.10
Specific surface area, As
cm2 cm-3
10
5.15
4.88
5.49
0.22
0.94
Porosity, P
%
10
43.42
40.58
45.59
1.63
6.00
Static angle of repose, θs
0
10
25.61
24.44
27.57
1.09
5.00
Coefficient of static Friction, µ
Steel sheet
Value
5
0.24
0.235
0.244
0.004
0
Plywood
Value
5
0.44
0.415
0.455
0.02
0
Rubber
Value
5
0.46
0.450
0.465
0.01
0
Aluminium
Value
5
0.37
0.361
0.375
0.01
0

The geometric mean diameter, sphericity, 1000mass, and surface area were in the ranges of 10.46–12.62 mm, 56.15–72.37%, 535.30–611.90 g, and 3.44–5.01 cm2; while Karaj and Muller [23] have reported 11.92 mm, 67.0%, 610.0 g, and 5.07 cm2, respectively which is quite in-line with the result of this investigation. The value obtained for sphericity (66.22%) is closer to the value of 64% as reported for by Sirisomboon et al. [31]. Judging by the criteria given by Bal and Mishra [6] and Garnayak et al. [15], which considered grain as spherical when the sphericity value is more than 0.80 and 0.70, respectively, as cited by Dash et al. [9]; JCS under this investigation can be referred to as nearly elliptical with mean sphericity of 66.22%.

Unit volume, Bulk volume, Weight, Density and Porosity
The unit volume, bulk volume, true density, and bulk density were in the ranges of 79.00–85.00 cm3, 144.00–148.00 cm3, 0.67–0.73 g cm-3, and 0.37–0.42 g cm-3, respectively. Karaj and Muller [23] also reported the true density and bulk density (for seed fractions with unit mass of 0.61 g) to be 0.662 g cm-3, and 0.373 g cm-3, respectively; which are in line with the outcome of this investigation. One thousand seed weight ranged between 535.30–611.90 g, with a mean value of 578.04 g. The porosity of 42.3% obtained by Karaj and Muller [23] was in the range of the present finding (40.58–45.59%). The value obtained (56.73%) by Sirisomboon et al. [31] is relatively high. The high value of porosity suggests that their aeration during deep bed drying is better than those with low value. An increased in porosity with moisture content were reported by Nimkar and Chattopadhyay [28] for green gram, Aydin [4] for hazel nuts, Milani et al.[25] for cucurbit seeds, [7] for roselle seed, Tavakoli et al. [33] for soybean grain, Davies and Zibokere [11] for cowpea, and Seyed et al. [30] for castor seed.

Surface area and Specific surface area
The surface area and specific surface area investigated were in the range of 3.44–5.01 cm2 and 4.88–5.49 cm2 cm-3, respectively. The range of surface area obtained was quite in-line with Karaj and Muller [23] who reported 5.07 cm2 at 9.0% db, while 5.34 cm2 reported by Sirisomboon et al. [31] was a bit above the range. An increase in surface area of JCS with moisture content was discovered. Similar trend of increase in surface area as moisture content increased has been found by Selvi et al. [29] for linseed, Isik and Unal [21] for red kidney bean grains, Garnayak et al. [15] for Jatropha curcas seed, Tavakoli et al. [33] for soybean grain, Davies and Zibokere [11] for cowpea, Bande et al. [8] for egusi melon seeds, and Idowu et al. [19] for sandbox seeds. Specific surface area obtained in this investigation is high (4.88–5.49 cm2 cm-3) when compared with 1.91 cm2 cm-3 obtained by Sirisomboon et al. [31] and 3.1 cm2 cm-3 obtained by Karaj and Muller [23]. The variation between the present and the former findings can be attributed to difference in the moisture content. It is evidence that specific surface area of JCS decreases as moisture content increased. 

Static angle of repose and Coefficient of static friction
The average static angle of repose of 25.61° was obtained at 7.5% db moisture content as against 30° obtained at 9.0% db by Karaj and Muller [23] and 37.76° obtained Sirisomboon et al. [31]. The variation can be attributed to differences in the moisture content. This can be explain with the fact that, at high moisture content the surface of seeds tends to be more viscous leading to high cohesion among the individual seeds and consequently resulted in higher value of static angle of repose. This implies that low flow ability of seeds was recorded at high moisture content. The increase in angle of repose with that of moisture content has been reported for roselle seed [7], soybean grains [33], cowpea [11], castor seed [30], and egusi melon seeds [8].

Coefficient of static friction against steel sheet, ply wood, rubber, and aluminium revealed that they were in ranges of 0.235–0.244, 0.415–0.455, 0.450–0.465, and 0.361–0.375, respectively. Coefficient of static friction against the surfaces examined was quite close with Karaj and Muller [23]; as they obtained 0.23, 0.44 and 0.35 for stainless sheet, rubber, and aluminium, respectively. The value obtained for rubber was the highest while steel sheet gave the lowest value (Tab. 1). Similar results (with rubber having the highest value of coefficient of static friction and steel sheet having the lowest value) have been found by some researchers: Nimkar and Chattopadhyay, [28] for green gram; Taser et al. [32] for Hungarian and common vetch seeds; Altuntas [3] for pumpkin seed and watermelon seed. Difference exists in the coefficient of static friction against plywood and wood. The difference can be largely attributed to differences in their surface smoothness. The coefficient of static friction for ply wood was in the range of 0.415–0.455 for the present investigation while Karaj and Muller [23] obtained 0.34 for wood.

CONCLUSIONS

The mean values of 17.56, 10.87, 8.23, and 11.62 mm were obtained for length, width, thickness, and geometric mean diameter, respectively. The mean of unit and bulk volume, true and bulk density, one thousand seed weight, and porosity were found to be 82.50 and 145.90 cm3, 0.70 and 0.40 g cm-3, 578.04 g, and 43.42%, respectively. Sphericity, surface area, specific surface area and static angle of repose investigated were 66.22%, 4.25 cm2, 5.15 cm2 cm-3 and 25.61°, respectively. The mean coefficient of static friction of 0.24, 0.44, 0.46 and 0.37 were obtained against steel sheet, plywood, rubber and aluminium, respectively. The result of the investigation provide useful data that can be use to develop necessary equipment and machines for planting, shelling, conveying, drying, aeration, storing, and  oil extraction from JCS found in North West Ecological Zone of Nigeria.

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Accepted for print: 13.12.2013
A.T. Salawu
No. 5 Augustine O. Salawu Street, Worgor Area, Ejigbo. Osun State. Nigeria
Department of Agricultural Engineering, Ahmadu Bello University, Zaria, Nigeria

email: atpsalawu@gmail.com

M.L. Suleiman
Department of Agricultural Engineering, Ahmadu Bello University, Zaria, Nigeria


M. Isiaka
Department of Agricultural Engineering, Ahmadu Bello University, Zaria, Nigeria

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