International Journal of Scientific Research in Environmental Sciences (IJSRES), 1 (11), pp. 337-343, 2013 Available online at http://www.ijsrpub.com/ijsres ISSN: 2322-4983; ©2013 IJSRPUB http://dx.doi.org/10.12983/ijsres-2013-p337-343 Full Length Research Paper Engineering Properties of Bitter Kola Nuts and Shell As Potentials for Development Processing Machines Rotimi Davies1*, Usman Shehu Mohammed2 1 Department of Agricultural and Environmental Engineering, Niger Delta University, Wilberforce Island, Amassoma, Bayelsa State, Nigeria 2 Department of Agricultural Engineering, Ahmadu Bello University, Zaria, Kaduna State, Nigeria * Correspondence:
[email protected] Received 09 September 2013; Accepted 24 October 2013 Abstract. The knowledge of engineering properties of any biomaterial is fundamental. It facilitates the design and development of equipment for harvesting, handling, conveying cleaning, delivering, separation, packing, storing, drying, mechanical oil extraction and processing of agricultural products. The study was conducted to investigate the physical, mechanical and frictional properties of bitter kola nut and shell, namely, axial dimensions, 1000 unit mass, arithmetic mean diameter, geometric mean diameter, surface area, sphericity, aspect ratio, bulk density, true density, porosity and angle of repose and coefficient of static friction were determined using standard methods. The engineering properties of bitter kola nut and shell were investigated at the moisture content of 20.8% and 23.1% dry basis respectively. The result obtained from the study revealed mean length, width, thickness, arithmetic and geometric diameter, sphericity, surface area and 1000unit mass ranged from 21.90-24.13 mm, 11.65-12.96 mm, 12.07-19.10 mm,15.21-22.03 mm, 14.55- 18.14 mm, 65- 75%, 447.9-1033.9 mm² and 3087.05- 3350.12 g respectively. The coefficient of static friction was determined for four frictional surfaces, namely, fibreglass, plywood, galvanized steel and rubber. The coefficient of static friction was the highest for bitter kola nut and shell on rubber surface and lowest for fiberglass. Key words: bitter kola, engineering properties, moisture content, axial dimension. 1. INTRODUCTION Bitter kola otherwise known as (Garcinia kola) is an important medicinal crop of the tropics. It regarded as one of the most important crops used in treating purgative, antiparasitic, antimicrobial, treatment of bronchitis, throat infections and prevention of relieve colic, cure head or chest colds and relieve cough in the continent of Africa. For bitter kola nut and shell, whose medicinal and economic potential are increases growing fast, there is much need to develop appropriate technology and equipment for various unit operations and to minimize the drudgery and improve the sanitation of the processing operations. This required the knowledge of physical properties of the crop. The knowledge of engineering properties of bitter kola nut and shell like any other biomaterial is fundamental because it facilitates the design and development of equipment for harvesting, handling, conveying cleaning, delivering, separation, packing, storing, drying, mechanical oil extraction and processing of agricultural products, their physical properties have to be known (Aviara et al., 2005; Davies, 2011). Presently, the equipment used in processing bitter kola nut and shell have been generally design without taken into cognizant the physical properties of bitter kola nut and shell which include the size, mass, bulk density, true density, sphericity, porosity, coefficient of static friction and angle of repose and resultant systems leads to reduction in working efficiency and increased product losses (Manuwa and Afuye, 2004; Razari et al., 2007). The engineering properties have been studied for various agricultural products by other researchers such as almond nut and kernel (Aydin, 2003), soybean (Manuwa and Afuye, 2004 Davies and El-Okene, 2009), African nutmeg (Burubai et al., 2007), caper fruit (Sessiz et al., 2005) cocoa bean (Bart-plange and Baryeh, 2002), jatropha seed and karanja kernel (Pradhan et al., 2008), gbafilo fruit and kernel and cowpea (Davies and Zibokere, 2011), pigeon pea (Shepherd and Bhardwaj (1986), locust bean seed (Ogunjimi et al., 2002), wheat (Tabatabaefa, 2003) and pistachio nut and its kernel (Razari et al ., 2007) and groundnut grain (Davies, 2009). Investigation was therefore carried out to determine the engineering properties of bitter kola nut and shell such as axial dimension, geometric and arithmetic mean diameter, sphericity, surface area, unit mass, 1000 grain mass, true volume, true and bulk densities, porosity, angle of repose and static coefficient of friction of bitter kola nut and shell in order to develop appropriate equipment that will alleviate laborious nature experience in processing the crop. 337 2. MATERIALS AND METHODS The bitter kola was bought from Abuloma market, Port Harcourt in Rivers state, Nigeria on 21th June, 2012. The sample was selected and cleaned manually to ensure that the bitter kola nut and shell were free of dirt, broken ones and other foreign materials. The bitter kola nut and shell were kept in the room temperature for five days. The experiments were conducted for the bitter kola at the moisture content levels of 20.1% for bitter kola nut and 23.8 % for bitter kola shell dry basis respectively. Three samples each weighing 15 g was placed in an oven set at 103 ± 2°C for 24 hours. Thus, seeds samples of the desired moisture level were prepared by adding calculated amount of distilled water and sealed in separate airtight polythene bags. The seed was kept in refrigerator at a temperature of 5 ℃ for one week to enable the moisture to distribute uniformly (Davies and El- Okene, 2009). To prepare bitter kola nut and shell with higher moisture contents, the required amount distilled water was calculated from the following equation and added to the samples (Kashaninejad et al., 2005): M − M 2 W2 = W1 × 1 100 − M 1 (1) where, W1 and W2 are mass of the sample and distilled water (g), and M1 and M2 are initial and final moisture contents (% d.b.) respectively. For this experiment, 100 bitter kola nut and shell were randomly selected, the length, width and thickness and mass of bitter kola nut and shell were measured using a micrometer screw gauge with a reading of 0.01 mm. The average diameter was calculated by using the arithmetic mean and geometer means of the three axial dimensions. The arithmetic mean diameter and geometric mean diameter of the bitter kola nut and shell were calculated according to Galedar et al., 2008 and Mohsenin, 1980. The sphericity was calculated based on Koocheki et al. 2007 and Milani 2007. The surface area was calculated according to McCabe et al ., (1986). The aspect ratio was determined according to Maduako and Faborode, (1990).The volume was calculated as cited by Miller (1987). The 1000 unit mass was determined using precision electronic balance to an accuracy of 0.01g. 50 randomly selected bitter kola nut and shell were weighed and multiplied by 20. The reported value was a mean of 20 replications. The bulk bitter kola nut and shell were put into a container with known mass and volume (500ml) from a height of 150 mm at a constant rate Bulk density was calculated from the mass of bulk seeds divided by the volume containing mass (Garnayak et al ., 2008). The true density was determined using the unit values of unit volume and unit mass of individual seed and calculated using the following relationship by Li et al . (2008). The porosity of the bulk bitter kola nut and shell was computed from the values of the true density and bulk density of the seed by using the relationship given by Mohsenin (1980). The static coefficient of friction for bitter kola nut and shell determined with respect to four test surfaces namely plywood, galvanized iron sheet, rubber sheet and fibreglass. A glass box of 150mm length, 100mm width and 40mm height without base and lid was filled with sample and placed on an adjustable tilting plate, faced with test surface. The sample container was raised slightly (5 – 10 mm) so as not to touch the surface. The inclination of the test surface was increased gradually with a screw device until the box just started to slide down and the angle of tilt was measured from a graduated scale. For each replicate, the sample in the container was emptied and refill with a new sample (Joshi et al ., 1993). The static coefficient of friction was calculated based on this equation, (Mohsenin, 1980). The static angle of repose with the horizontal at which the material will stand when piled. This was determined using topless and bottomless cylinder of 0.15 m diameter and 0.25 m height. The cylinder was placed at the centre of a raise circular plate having a diameter of 0.35m and was filled with bitter kola nut and shell. The cylinder was raised slowly until it formed a cone on a circular plane. The height of the cone was measured and the filling angle of repose was calculated based on the following relationship established by (Karababa, 2006 and Kaleemullah and Gunaseka, 2002). 3. RESULTS AND DISCUSSIONS Some engineering properties such as axial dimensions, arithmetic and geometric mean diameter, sphericity, volume, 1000 unit mass and surface area of bitter kola nut and shell investigated at moisture content are presented in Table 1.These parameters were investigated at moisture content 20% for bitter kola seeds and 23.7% for dry basis. The mean length, width and thickness of bitter kola seeds ranged between 17.20-26.51 mm and 32.66-22.56, 9.43-14.73 mm and 12.09-16.31, 10.50-13.73 mm and 17.7422.10 respectively. The corresponding mean size of the fresh dura palm kernel were length, width and thickness were found to be 30.25 mm, 19.94 mm and 15.66 mm, respectively (Owolarafe et al., 2007). The corresponding values of axial dimensions for palm kernel (Dura variety), average length, width and thickness ranged from 26.50 - 44.00 mm, 16.50 28.00 mm and 21.50 -34.50mm respectively (Mijinyawa and Omoikhoje, 2005). The parameters are essential for the design of appropriate equipment for processing such as cleaning, sorting, packaging and storage processes. The values of the measured parameters and the corresponding values indicated that the machines required for utilization and processing these products would be different. The mean geometric and arithmetic mean diameter of bitter kola seeds ranged from 12.38 to 18.15 mm and 17.46 to 23.69 mm and11.94 to17.28 mm and 16.91 to 22.75 mm respectively. The geometric and arithmetic mean diameters of palm fruit ranged from 21.36 to 29.23 mm and 20.80 to 27.80 mm (Davies, 2012). The corresponding values for watermelon as reported Koocheki et al. (2007) were 6.89 and 8.24mm for Kolaleh, 8.37 and 10.79 mm for Ghemez and 7.61 and 9.28 mm for Sarakhsi at moisture content of 5.02, 4.75 and 4.55% wet basis. The mean surface area of bitter kola nut and shell were 447.9mm² and 898.4mm².Themean surface area of gbafilo fruit and kernel ranged from 1584.80 to 2455.90 mm² and 737.37 to 1378.90 mm² (Davies and Zibokere et al., 2011). The mean sphericity value ranged from 65% to 68% for bitter kola nut and 69% to 75% for bitter kola shell. The sphericity was observed for C. lunatus, 53%, C. edulis, 47% and C. vulgaris, 45% (Davies and Zibokere et al ., 2011). The mean sphericity of bitter kola shell and nut were significantly different (P<0.05). Galedar et al. (2008) reported sphericity for pistachio nut at moisture content of 5.83% and kernel at moisture content of 6.03% were 69.34% and 72.59% respectively. According to Bal and Mishra (1988) and Garnyak (2008) considered any grain, fruit and seed as spherical when the sphericity value is above 80 and 70% respectively. Therefore, it can be concluded that bitter kola shell is spherical based on the sphericity values falls within the acceptable range. The aspect ratio of bitter kola shell and nut was 54.83% and 53.59%. It can be concluded that the bitter kola shell and nut will roll. This tendency to roll is very important in the design of hoppers.1000 unit mass of bitter kola nut ranged from 3087.02 to 4200.35 g and 3112.74 to 4105.16 g for bitter kola shell. The corresponding values reported for japtropha seed and kernel, arigo seed, simarouba fruit and kernel, maize, red gram, wheat, green gram, chickpea, faba bean, pigeon pea were 1322.41, 688, 1124.7(±111.3), 1120(±52.54), 330.26(±29.35), 268.30(±0.002), 102(±0.06), 346 g, 30.15 g, 120 g and 75 g respectively (Dash et al., 2008; Dulta et al., 1998; Shephered and Bhardwaj, 1986; Tabatabaeefar, 2003). Table 2 showed the result of true and bulk densities, porosity, angle of repose and coefficient of friction bitter kola nut and shell. It was observed that mean porosity bitter kola nut and shell corresponded to 35.60%, 0.97 and 40.70%, 1.21. The corresponding values of simarouba fruit and kernel were 33.2 ±2.03 and 28.6% ±2.9. Burubai et al. (2007) reported porosity of 41% ±4.2 for nutmeg. The values obtained for porosity is solely dependent on the true and bulk density. This can be furthered explained from obtained result that air circulation through the products will be more pronounced in bitter kola nut compared to bitter kola shell. The result of true and bulk densities, angle of repose and coefficient of friction for bitter kola seed and shell were presented in Table 2. The mean values for true and bulk densities bitter kola seed and shell were 946.53±24.09, 873.61±43.17, 609.50±6.32 and 621±4.20 kgm-3. The corresponding values for true and bulk densities for nutmeg and simarouba fruit and kernel were 836.54, 488.76, 622.27 and 727.27 kgm-3. The true and bulk densities values of melon seeds, nutmeg and simarouba were significantly difference at 0.05 probability level (Burubai et al., 2007). Palm fruit and kernel had the bulk density 0.64g/m3 and0.71g/m3 (Davies, 2012).The corresponding values as reported by Owolarafe et al. (2007) for true density, bulk density and porosity of fresh dura were 1112.50kg/m 3 and 995.70kg/m3 respectively. The coefficient of static friction on the tested surfaces namely: glass, plywood and galvanized iron sheet and rubber sheet revealed significant difference at 0.05 probability level. Bitter kola seed and shell on the fibreglass surface had the lowest coefficient of static friction compared to other tested surfaces. However, coefficient of static friction for bitter kola nut was found to be the higher than bitter kola shell. Bitter kola nut and shell experienced highest static coefficient of friction on rubber surface. Tabatabaeefar (2007) observed similar trend in the static coefficient of friction of wheat. He recorded lowest static coefficient of friction on glass surface, followed by galvanized iron sheet and lastly plywood. The mean angle of repose for bitter kola nut and shell were 33.7˚and 21.9˚.The corresponding angle of repose for simarouba fruit and kernel is lower than jatropha seed and kernel. While pistachio nut and kernel were less than bitter kola nut and shell (Sirissonmboon et al., 2007; Galedar et al., 2008). The mean fracture force required to rupture the bitter kola nut and shell on horizontal position were 295±3.76 and 21±0.19 N. The mean fracture force required to break the bitter kola nut and shell vertical position were 321.6±10.49 and 24.0±1.05 N. The average force required to break the dura and tenera palm kernel according to Owolarafe et al. (2007) were 2301N and 1149N. Table 1: Physical properties of bitter kola nut and shell Properties Length (mm) Width (mm) Thickness(m m) Arithmetic mean diameter (mm) Geometric mean diameter(m m) Sphericity(%) 1000-unt mass (g) Surface area(mm2) Volume (mm3) Aspect ratio (%) Sample no 100 100 100 100 Bitter kola nut Maximum 26.51 14.73 13.73 18.15 Minimum 17.20 9.43 10.50 12.38 Mean 21.90 11.65 12.07 15.21 Bitter kola shell Maximum Minimum 32.66 22.56 16.31 12.09 22.10 17.74 23.69 17.46 Mean 24.13 12.96 19.10 22.03 100 17.28 11.94 14.55 22.75 16.91 18.14 100 50 100 100 100 65 4200.35 938.2 2701.28 55.56 69 3087.02 447.9 891.83 54.83 68 3252.6 1 665.2 1612.62 53.19 69 4350.16 1626.2 6164.78 49.94 74 3112.74 898.4 2533.81 53.59 75 3305.2 7 1033.9 3127.88 53.7 Table 2: Gravimetric and frictional properties bitter kola fruit and nut at moisture at 8.3% dry basis Properties True density (kgcm-3) Bulk density (kgm-3) Porosity (%) Angle of repose(˚) Fibreglass Galvanised iron sheet Plywood sheet Rubber sheet Fx Vertical fracture force (N) Fy Horizontal fracture force (kN) S.E.M- Standard error of means. Bitter kola fruit Mean (±S.E.M) 946.53±24.09 690.50±6.23 35.60±0.97 33.5±0.07 ˚ 0.35±0.02 0.46±0.01 0.51±0.02 0.53±0.02 195±3.76 321.6±10.49 Bitter kola shell Mean (±S.E.M) 873.61±43.17b 621±4.20 40.70±1.21 21.9±0.04 ˚ 0.29±0.02 0.33±0.01 0.39±0.07 0.43±0.03 21±0.19 34.0±1.05 4. CONCLUSION The following conclusions are drawn from the investigation on the some engineering properties of bitter kola nut and shell at moisture content of 6.33% and 5.21% dry basis respectively: (1) The physical properties of bitter kola nut and shell such as mean length, width, thickness, arithmetic and geometric mean diameter, sphericity, surface area, 1000unit mass and aspect ratio were investigated; (2) The mean porosity, true and bulk densities, angle of repose was investigated for the bitter kola nut and shell. 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Dr. Rotimi Davies is a lecturer in the Department of Agricultural and Environmental Engineering, Niger Delta University (NDU), Wilberforce Island, Amassoma, Bayelsa State, Nigeria. He is a certified Engineer, a registered member of the Council for the Regulation of Engineering in Nigeria (COREN). Dr. Rotimi Davies bagged his B.Sc. (Hons) and master’s degrees in Agricultural Engineering from the premier University of Ibadan, Ibadan, Nigeria. He later obtained his doctorate degree in Agricultural Engineering from the renowned Ahmadu Bello University (ABU), Zaria, Kaduna State, Nigeria. His areas of specialization are Bio-energy, Crop Processing and Storage Engineering. Dr. Rotimi Davies is a dynamic and an outstanding Engineer who has published many research articles in international journals. Dr. Rotimi Davies had held quite a number of administrative positions but presently, he is the Staff and Undergraduate Students’ Seminars and Projects Coordinator of the Department of Agricultural and Environmental Engineering at NDU. Dr. Usman Shehu Mohammed is an Associate Professor in the Department of Agricultural Engineering, Ahmadu Bello University (ABU), Zaria, Kaduna State, Nigeria. He is a certified Engineer, a registered member of the Council for the Regulation of Engineering in Nigeria (COREN). He obtained his first, master’s and doctorate degrees in Agricultural Engineering from the prestigious ABU in 1984, 1999 and 2001 respectively. Dr. Mohammed specializes on Farm Power and Machinery. He is an astute lecturer and researcher who has published numerous referred articles in local and international journals. His hobbies are basketball, squash and athletics. Dr. Mohammed had held several administrative positions at ABU but presently, he is the Departmental Postgraduate Coordinator of Agricultural Engineering.