Assessment of Physical Properties of Castor Seeds with Variety F. A. Oluwole* 1, N. A. Aviara 2, B. Umar 2 and A. T. Abdulrahim 1

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1 University of Maiduguri Annals of Borno Volume XXVI, June 2016 Assessment of Physical Properties of Castor Seeds with Variety F. A. Oluwole* 1, N. A. Aviara 2, B. Umar 2 and A. T. Abdulrahim 1 1 Department of Mechanical Engineering, University of Maiduguri Maiduguri, Nigeria 2 Department of Agricultural and Environmental Resources Engineering University of Maiduguri, Maiduguri, Nigeria *engrfasiu@yahoo.com; oluwole@unimaid.edu.ng; ABSTRACT Some physical properties of castor seeds were determined with a view to classifying the varieties and exploring the possibility of developing shelling and dehulling equipment for this important seed oil yielding crop. Four varieties were identified on the basis of colour and size and named White Big Size (WBS), Black Big Size (BBS), Grey Medium Size (GMS) and Grey Small Size (GSS) respectively. The physical properties studied were geometrical properties (size and shape); gravimetrical properties (mass, volume, porosity, particle and bulk densities) and frictional properties (angle of repose and coefficient of static friction). At the dry basis moisture content of 6.05, 7.19, 7.68 and 5.75% for WBS, BBS, GMS and GSS varieties respectively, the major, intermediate and minor diameters were 17.69, 16.34, 14.27, 8.97 mm; 13.12, 12.33, 9.08, 6.10 mm and 7.93, 7.19, 5.71, 4.56 mm respectively; the volumes were , , and for the WBS, BBS, GMS and GSS respectively. The sphericity and aspect ratio ranged from to and to depending on the variety. One thousand seed weight and particle mass were kg and 0.77 g (WBS), kg and 0.59 g (BBS), kg and 0.32 g (GMS) kg and g (GSS). Particle and bulk densities and porosity ranged from kgm -3 to kgm -3, kgm -3 to kgm -3 and 20.20% to 27.70% respectively depending on the variety. Angle of repose and coefficient of static friction varied from O to O and to depending on the variety and the structural surface. The geometric, gravimetric and frictional properties of WBS and BBS castor varieties were higher than those of the GMS and GSS varieties because they are larger in size and have rougher surface. Key words: Castor seed, ricinus communist, geometrical properties, gravimetrical properties, frictional properties. INTRODUCTION The castor crop, (Ricinus communist L.) is a member of the Euphorbiaceae. In Nigeria, castor seed is obtained abundantly in every part of the country. It contains 40 to 60 % oil (Akpan, et al. 2006). The Yorubas call it Lara, the Hausas refer to it as Zurma, and the Kanuris call it Kwolakwola, while the Igbos refer to it as Kpikpi(Oluwole, 2010). Annals of Borno, Volume XXVI, 2016 Page 85

2 F. A. OLUWOLE* 1, N. A. AVIARA 2, B. UMAR 2 AND A. T. ABDULRAHIM 1 The oil extracted from it is traditionally used as medicinal ointment, illuminant, and soap making raw material. At present, the potentials of castor oil are not fully explored in Nigeria. Plate 1 shows pods of four varieties of the seeds that have been identified. These have been named as White Big Sized (WBS), Black Big Sized (BBS), Grey Medium Sized (GMS) and Grey Small Sized (GSS). Olaoye (2000), in his work on some physical properties of castor pods named the varieties using their local names (Ojji, Evahura and Osbowu). Pods: A B C D Plate 1. Different varieties of Castor pods containing castor seeds The pod can contain up to three seeds, which are flat and oval in shape, with shiny brittle tester enclosing a white, soft, highly oleaginous kernel (Plate 2). Plate 2. Castor Kernels: A - White Big Size (WBS); B - Black Big Size (BBS); C - Grey Medium Size (GMS); D - Grey Small Size (GSS) The derivatives of castor oil are at par with petrochemical products for use in several industrial applications. In fact, they are considerably superior since they are from renewable sources, bio-degradable and eco-friendly. Castor oil is regarded as one of the most valuable laxatives in medicine. It forms a clean, light-coloured soap, which dries and hardens well and is free from smell. It is an excellent solvent of pure alkaloids and Annals of Borno, Volume XXVI, 2016 Page 86

3 Assessment of Physical Properties of Castor Seeds with Variety such solutions of Atropine, cocaine, etc, as are used in ophthalmic surgery. It is also dropped into the eye to remove the after-irritation caused by the removal of foreign bodies. It is finding increasing uses in the industrial world. It figures largely in the manufacture of the artificial leather used in upholstery; it furnishes a colouring for butter, and from it is produced the so-called Turkey red oil used in the dyeing of cotton textures. It is an essential component in some artificial rubbers, in various descriptions of celluloid, and in the making of certain water proof preparations, and one of the largest uses is in the manufacture of transparent soaps. It also furnishes sebacic acid which is employed in the manufacture of candles, and caprylic acid, which enters into the composition of, vanishes, especially suitable for the polishing of high-class furniture and carriage bodies. Castor oil and its derivatives are also used in the production of paints, lacquers, and other protective coatings, lubricants and grease, hydraulic fluids, biodiesel, printing inks linoleum, oil cloth and as a raw material in the manufacturing of various chemicals sebacic acid and undecylenic acid, used in the production of plasticizer and Nylon (Oluwole, 2010). The processing of castor seeds to obtain its oil involves sequence of operations as described by Akpan, et al The present methods of carrying out these operations, involve manual labour, which are not only labour- and time-consuming but also wasteful. Improved methods of processing the seed using suitable machines and equipment can be developed if the relevant physical properties are known. The objective of this study is to investigate some physical properties of castor seeds and their variation with variety.akaniet al. (2000) reported that inadequate engineering data on our indigenous crops have retarded the development of indigenous technology for the processing of these crops. Availability of these data would boost the design and development of machine for processing of indigenous crops. The properties that were considered included moisture content, axial dimensions, particle and bulk densities, porosity, coefficient of static and kinetic frictions, angle of repose, shape and surface area, roundness and sphericity, volume, mass of one thousand nuts/seeds and energy needed to crack/shell seeds/nuts.aviaraet al. (2005) and Oluwoleet al. (2007a) reported the determination of moisture content of oil seeds or nuts by oven drying of the samples at 130 O C for six hours, with weight loss monitored on hourly basis to give an idea of the time at which the weight begins to remain constant. Determination of the axial dimensions of seeds have been carried out by randomly selecting one hundred seeds and measuring the three principal axial dimensions; major, intermediate and minor diameters measured using a verniercaliper reading to 0.05 mm as reported by Aviaraet al., (2005) for guna seed and sheanut, and Fathollazadehet al., (2008) for groundnut kernel, areca nut kernel, apricot kernel (CV. SonnatiSalmas) soy Annals of Borno, Volume XXVI, 2016 Page 87

4 F. A. OLUWOLE* 1, N. A. AVIARA 2, B. UMAR 2 AND A. T. ABDULRAHIM 1 bean. they investigated the variation of these dimensions with moisture content for respective seeds and kernels. Aviaraet al. (2005) employed the arithmetic mean, geometric mean and equivalent sphere effective diameter of the three principal axes in calculating the volume of the seed. The results reported showed that these diameters approximately predicted the experimentally determined values. Oluwole (2010) reported that in a similar work by Aviara on guna seeds, it was the geometric diameter that gave the closest value to the experimentally determined volume of guna seeds. In another work on sheanut, Aviaraet al. (2005) reported that the equivalent sphere effective diameter gave the closest value to the experimentally determined volume. Two methods of determining the particle density of agricultural materials have been utilized by investigators. These include the gas displacement method as reported by Aviaraet al. (2005) and the water displacement method Eke et al., 2007; Simonyan, et al. 2007; Asoegwuet al. 2006; and Aviaraet al. 2005). Bulk density has been determined using the AOAC (1990) recommended method. The relationship between porosity, particle density and bulk density as stated by Mohsenin (1986) has been used to calculate the porosity of grains and seeds. Different methods have been used in studying the coefficient of friction of agricultural products on different structural surfaces. These include moving a given surface against the material as reported by Oluwole (2010), tilting an incline plane (Aviaraet al. 2005; Oluwole, 2004; Mohsenin, 1986) to the shear box equipment as reported by Aviaraet al. (2005). The structural surfaces employed are galvanized steel sheet, plywood, Formica and glass. Investigators (Oluwole, 2004 and Aviaraet al. 2005), using a specially constructed box with removable front panel, have conducted studies on the angle of repose of nuts and seeds. MATERIALS AND METHODS Materials Bulk quantities of four different varieties of castor pods used in this study were obtained from farmers in Kawuri village of Konduga Local Government Area, Borno State, Nigeria. The pods were prepared for various investigations by cleaning (removing dirt and stones by hand picking), and stored in polyethylene bags according to varieties namely: A- WBS; B- BBS; C- GMS; and D- GSS. Each variety was kept under shade for 2 days to equilibrate. About 15 kg of pods was taken from each variety and were manually shelled to obtain intact seeds. The seeds were stored in separate sealed polyethylene bags to maintain the moisture level of the samples. Annals of Borno, Volume XXVI, 2016 Page 88

5 Assessment of Physical Properties of Castor Seeds with Variety Determination of Moisture Content Since the seeds are oil yielding, the moisture contents were determined using the method reported by ASAE (1983), Aviaraet al. (2005), Oluwoleet al. (2007a & b). This method involves oven drying of samples at 130 O for 6 hours. Determination of Physical Properties To determine the axial dimensions, 100 seeds were randomly selected from each variety of castor seed following the method employed by Aviaraet al. (2005). For each seed, the three principal axial dimensions, namely the major, intermediate and minor axes were measured using verniercalliper reading to 0.05 mm.from each of the samples, one thousand seeds weight was obtained using an electronic balance reading to g. This was replicated five times and the average taken as one thousand seed weight. The particle density was determined for each variety using water displacement method as described by Aviaraet al. (2005). Thirty seeds each coated with very thin layer of epoxy resin to prevent the absorption of water during the experiment were used. The increase in weight due to the adhesive was negligible. Each was weighed using an electronic balance reading to g and submerged in water contained in a calibrated measuring cylinder. The volume of water displaced was recorded as the volume of the sample. Bulk density was determined using the AOAC (1990) recommended method. This involved the filling of a 1500 ml cylinder with the samples from a height of 15 cm and weighing the contents with an electronic balance weighing to g. Porosity was calculated from the particle and bulk densities using the relationship given by Mohsenin (1986). In determining the angle of repose, a specially constructed open-ended box made of plywood and 150 x 150 x150 mm in size with a removable front panel, was used. The box was placed on a table and filled with the samples. The front panel was quickly removed to allow the material to slide and assume its natural slope in bulk. The angle of repose was determined by measuring the depth of the free surface at the end of the box and the horizontal distance from the end of the box to the lowest end of the slope. The inclined plane method as described by Mohsenin (1986) and Aviaraet al. (2005) was used to evaluate the coefficient of static friction of the samples on four structural surfaces, namely galvanized steel sheet, formica, plywood with fibres parallel to the direction of movement and plywood with fibres perpendicular to the direction of movement. This involved the placing of an open-ended box on an adjustable tilting surface which was made from a structural surface. The box was filled with the samples and the structural surface with the box and its content on top was gradually raised with a screw device until the box just started sliding down. Annals of Borno, Volume XXVI, 2016 Page 89

6 F. A. OLUWOLE* 1, N. A. AVIARA 2, B. UMAR 2 AND A. T. ABDULRAHIM 1 RESULTS AND DISCUSSION Moisture Contents The moisture contents determined for the four varieties WBS, BBS, GMS and GSS used in this study were 6.05%, 7.19%, 7.68% and 5.74% respectively. Geometrical Properties The geometric properties (axial dimensions, arithmetic mean, geometric mean, square mean and the equivalent diameters, sphericity and aspect ratio) with the mean value, standard deviation and coefficient of variation for the castor seed varieties studied are presented in Table 1. Table 1. Geometrical Properties of Castor Kernels Geometrical Properties A-White Big Size (WBS) B-Black Big Size (BBS) Major Diameter L1 (mm) ±0.67 (3.79) Intermediate Diameter L ±0.57 (mm) (4.34) Minor Diameter L3 (mm) 7.93 ±0.44 (5.55) (AMD) F1= ±0.48 (L1+L2+L3)/3 (3.72) (GMD) F2 = (L1L2L3) 1/ ±0.47 (3.84) (SMD) F3= ±0.47 [(L1L2+L2L3+L3L1)/3] 1/2 (3.73) EQD = (F1+F2+F3)/ ±0.48 (3.78) Sph = F2/L ±0.014 (2.02) AR = L2/L ±0.021 (2.83) ±0.90 (5.51) ±0.51 (4.14) 7.19 ±0.33 (4.59) ±0.57 (4.77) ±0.52 (4.59) ±0.53 (4.58) ±0.54 (4.64) ±0.010 (1.44) ±0.016) (2.12) C-Grey Medium Size (GMS) ±0.31 (2.12) 9.08 ±0.27 (2.97) 5.71 ±0.18 (3.15) 9.69 ±0.17 (1.75) 9.11 ±0.25 (2.74) 9.36 ±0.17 (1.79) 9.39 ±0.18 (1.92) ±0.014 (2.20) ±0.021 (3.30) D- Grey Small Size (GSS) 8.97 ±0.44 (4.91) 6.10 ±0.39 (6.39) 4.56 ±0.18 (3.95) 6.54 ±0.31 (4.74) 6.29 ±0.28 (4.45) 6.41 ±0.30 (4.68) 6.42 ±0.30 (4.67) ±0.015 (2.14) ±0.028 (4.12) Values in parentheses are Coefficient of variation With known axial dimensions, the seeds can be effectively graded and appropriate sieves can be designed within a range for separation of the seeds from the chaff. It is also observed from Table 1 that the AMD has the highest value and the GMD has the least Annals of Borno, Volume XXVI, 2016 Page 90

7 Assessment of Physical Properties of Castor Seeds with Variety value for all the varieties studied. The values of (SMD) and (EQD) are almost the same for all the varieties studied. These results can be used to determine the aerodynamic properties of the seeds. The value of the sphericity (Sph) and aspect ratio (AR) shows that the GSS has the tendency to roll while the other three varieties (WBS, BBS and GMS) have the tendency to slide. This information will help in designing handling and processing equipment for the seeds. The low value of coefficient of variation (CV) of between 1.44% and 6.39% indicate that they were uniformly dispersed about their mean values. Gravimetrical Properties Table 2 presents the mean value, standard deviation and coefficient of variation of the gravitational properties of four varieties of castor seeds. It is observed from these values that the bigger the variety the smaller the particle and bulk densities of the castor seeds. This information will help in developing appropriate processing equipment for the processing/handling of castor seeds. Table 2. Gravimetrical Properties of Castor Kernels Gravimetrical Properties A-White Big Size (WBS) B-Black Big Size (BBS) Volume (mm 3 ) ±8.70 (6.57) ±17.30 (16.62) 0.59 ±0.059 (10.00) ±37.90 (6.27) ±11.34 (2.35) C-Grey Medium Size (GMS) ±4.50 (10.37) D- Grey Small Size (GSS) ±2.10 (12.88) Mass (g) 0.77 ± ± ±0.022 (12.60) (13.13) (17.89) Particle Density ρp ± ± ±22.80 (kg/m 3 ) (5.49) (4.38) (2.77) Bulk Density ± ± ±14.36 ρb(kg/m 3 ) (3.37) (1.45) (2.36) Porosity Рo % Mass of 1000 seeds ± ± ± ±0.003 W1000 (kg) (0.27) (0.99) (0.91) (2.56) Values in parentheses are Coefficient of variation Frictional Properties It is observed from Table 3 that the angle of repose of the (WBS) and (BBS) are the same while that of the (GMS) and (GSS) are also the same. However, the coefficient of static Annals of Borno, Volume XXVI, 2016 Page 91

8 F. A. OLUWOLE* 1, N. A. AVIARA 2, B. UMAR 2 AND A. T. ABDULRAHIM 1 friction on four different structural surfaces varies with varieties. The (WBS) has the highest values, followed by the (GSS) and the (BBS). The (GMS) has the least values. These results would have impacts on designing equipment for handling the seeds. Table 3. Frictional Properties of Castor Kernels Coefficient of static friction Frictional Properties A-White Big Size (WBS) Angle of Repose deg ±1.406 (6.45) Formica ±0.005 (1.69) Steel Sheet ±0.017 (5.04) Plywood with grain Parallel to the direction of movement Plywood with grain Perpendicular to the direction of movement ±0.008 (2.37) ±0.017 (4.59) Values in parentheses are Coefficient of variation B-Black Big Size (BBS) ±0.436 (2.01) ±0.007 (2.41) ±0.004 (1.21) ±0.022 (7.03) ±0.014 (4.01) C-Grey Medium Size (GMS) ±0.629 (3.45) ±0.006 (2.09) ±0.015 (4.62) ±0.006 (2.03) ±0.010 (2.93) D- Grey Small Size (GSS) ±1.08 (5.92) ±0.008 (2.73) ±0.011 (3.33) ±0.011 (3.47) ±0.012 (3.37) CONCLUSION The investigation of the physical properties of four varieties of castor seeds revealed the following: 1. The castor seeds can be distinguished by their colour and size as follows: (A- White Big Size (WBS), Black Big Size (BBS), Grey Medium Size (GMS) and Grey Small Size (GSS). 2. At the moisture content of 6.05%, 7.19%, 7.68% and 5.75% for the WBS, BBS, GMS and GSS the mean values of the major diameters (L1) ranged from 8.97 ±0.44 to17.69 ±0.67 mm, the intermediate diameters (L2)ranged from 6.10 ±0.39 to ±0.57 mm and the minor diameters (L3) ranged from4.56 ±0.18 to 7.93 ±0.44 mm with the WBS variety having the highest value and the GSS variety having the lowest value. Annals of Borno, Volume XXVI, 2016 Page 92

9 Assessment of Physical Properties of Castor Seeds with Variety 3. The arithmetic mean diameter (AMD) ranged from 6.54 ±0.31mm to12.91 ±0.48 mm, the geometric mean diameter (GMD) ranged from 6.29 ±0.28 mm to 12,25 ±0.47 mm. The square mean diameter (SMD) ranged from 6.41 ±0.30 mm to ±0.47 mm while the equivalent diameter (EQD) ranged from 6.42 ±0.30 mm to ±0.48 mm with the WBS variety having the highest value and the GSS variety having the lowest value. 4. The mean values of volumes ranged from ±2.10 m 3 to ±8.70 m 3 with the WBS variety having the highest value and the GSS variety having the lowest value. 5. The mean values of mass ranged from ±0.022 g to 0.77 ±0.097g with the WBS variety having the highest value and the GSS variety having the lowest value. 6. The mean values of particle density ranged from ±31.43 kg/m 3 to ±22.80 kg/m 3 with the GSS having the highest value. 7. The mean values of bulk density ranged from ±15.03 kg/m 3 to ±14.36 kg/m 3 with the GSS having the highest value. 8. The values of porosity ranged from 20.20% to 27.70% with the BBS having the least value and the GMS having the highest value. 9. The one thousand seeds weight ranged from ±003 kg to ±0.002 kg, with the WBS having the highest value. 10. The angle of repose of the (WBS) and (BBS) are the same while that of the (GMS) and (GSS) are also the same. 11. The coefficient of friction ranged from to on Formica; to on steel sheet; to on plywood with parallel grains to the direction of movement and to on plywood with grains perpendicular to the direction of movement. REFERENCES Akani, A.O., Ohanwe, C.N. and Omoniyi, I.O. (2000). Determination of Optimum impact for decortication of bambara groundnut. Proceedings of the Nigerian Institution of Agricultural Engineers, 22, Akpan, U. G., Jimoh, A.and Mohammed, A. D. (2006). Extraction, Characterization and Modification of Castor Seed Oil. Leonardo Journal of science AOAC, (1990). Official method of analysis. 15 th edition. Association of official analytical chemists, Washington DC. ASAE (1983). ASAE standards: ASAE Moisture measurement- Grains and seeds. American Society of Agric. Engineers. St. Joseph, Michigan. Annals of Borno, Volume XXVI, 2016 Page 93

10 F. A. OLUWOLE* 1, N. A. AVIARA 2, B. UMAR 2 AND A. T. ABDULRAHIM 1 Asoegwu, S.N., Ohanyere, S.O., Kanu, O.P., and Iwueke, C.N. (2006). Physical Properties of African Oil Bean (Pentaclethramacrophylla) Agricultural Engineering International: the CIGR Ejournal. Manuscript FP Vol. VIII. Aviara, N.A., Oluwole, F.A. and Haque, M.A. (2005). Effect of moisture content on some physical properties of sheanut(butyrospernumparadoxum). Int. Agrophysics, 19, Eke, C.N.U., Asoegwu, S.N. and Nwandikom, G.I. (2007). Physical properties of Jackbean (canavaliaensiformis). Agricultural Engineering International: the CIGR Ejournal. Manuscript FP Vol. IX. Fathollazadeh, H., Mobli, H., Beheshti, B., Jafari, A. and Borghei, A.M. (2008). Effect of moisture content on some physical properties of Apricot kernel (C.V.SonnatiSalmas). Agricultural Engineering International: the CIGR Ejournal. Manuscript FP Vol. X. Mohsenin, N.N. (1986). Physical properties of plant and animal material. 2 nd edition (reversed) Gordon and Breach Science Publications. New York. Olaoye J.O, (2000). Some physical properties of castor seed relevant to design of processing equipment, Journal of agricultural Engineering research, 77, Oluwole, F.A. (2004). Design, construction and performance evaluation of a sheanut cracker. Unpublished M Sc. Dissertation. University of Maiduguri, Nigeria. Oluwole, F.A., Aviara, N.A. and Haque, M.A. (2007a). Effect of moisture content and impact energy on the crackability of sheanut Agricultural Engineering International: the CIGR Ejournal. Manuscript FP Vol. IX. Oluwole F.A., Abdulrahim A.T., and Olalere R.K. (2007b). Effect of moisture content on crackability of bambara groundnut using a centrifugal cracker. Int Agrophysics, 21, Oluwole, F.A. (2010). Some Physical Properties of Castor Seeds. Unpublished non-thesis Ph.D seminar II, University of Maiduguri, Nigeria. Simonyan, K.J., El-Okene, A.M. and Yiljep, Y.D. (2007). Some physical properties of samara sorghum 17. Agricultural Engineering International: the CIGR Ejournal. Manuscript FP Vol. VIII. Annals of Borno, Volume XXVI, 2016 Page 94