Effect of moisture content on physical properties of some grain legume seeds

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1 New Zealand Journal of Crop and Horticultural Science ISSN: (Print) (Online) Journal homepage: Effect of moisture content on physical properties of some grain legume seeds Ebubekir Altuntas & Hilal Demirtola To cite this article: Ebubekir Altuntas & Hilal Demirtola (2007) Effect of moisture content on physical properties of some grain legume seeds, New Zealand Journal of Crop and Horticultural Science, 35:4, , DOI: / To link to this article: Published online: 19 Feb Submit your article to this journal Article views: 1469 View related articles Citing articles: 7 View citing articles Full Terms & Conditions of access and use can be found at Download by: [ ] Date: 16 December 2017, At: 00:40

2 New Zealand Journal of Crop and Horticultural Science, 2007, Vol. 35: /07/ The Royal Society of New Zealand Effect of moisture content on physical properties of some grain legume seeds EBUBEKIR ALTUNTAS HILAL DEMIRTOLA Department of Agricultural Machinery Agricultural Faculty Gaziosmanpasa University Tasliciftlik, Tokat, Turkey Abstract This study was carried out to determine the effect of moisture content on physical properties of some grain legumes seeds such as kidney bean (Phaselous vulgaris), dry pea (Pisum sativum), and black-eyed pea (Vigna sinensis) seeds. Three different moisture contents for each grain legume were evaluated. The average length, width, thickness, geometric mean diameter, and unit mass of seeds ranged from 16.66, 8.86, 7.17, 10.17mm, and 0.715g for kidney bean; 7.46, 6.02, 4.49, 5.85mm, and 0.158g for pea; 9.19, 6.96, 6.26, 7.32mm, and g for black-eyed pea at a moisture content of 8.21%, 8.20%, and 5.66% (wet basis), respectively. The sphericity, thousand-seed mass (1000-seed mass), and projected area increased, whereas the bulk and kernel densities linearly decreased with an increase in moisture content for each grain legume seed. The porosity, the volume of seed, and angle of repose increased for three grain legumes seeds, whereas the angle of repose decreased for blackeyed pea seeds in the moisture contents studied. The static and dynamic coefficients of friction on various surfaces, namely, galvanised metal, chipboard, mild steel, plywood, and rubber also linearly increased with an increase in moisture content of each grain legume seed. Keywords grain legumes ; kidney bean; Phaselous vulgaris; pea; Pisum sativum; black-eyed pea; Vigna sinensis; physical properties H07011; Online publication date 15 November 2007 Received 19 January 2007; accepted 27 August 2007 INTRODUCTION Kidney bean (Phaseolus vulgaris L.) is well known in many cultures throughout the world as an edible legume. The largest commercial producers of dried common beans are India, China, Indonesia, Brazil, and the United States. Dried beans are generally available in prepackaged containers as well as in bulk bins. The popular kidney-shaped beans are very good sources of cholesterol-lowering fibres (World's Healthiest Foods 2006). In Turkey, kidney bean has been widely cultivated as a legume crop on ha with an annual production of t (FAO 2004). Pea (Pisum sativum L.) is a small, edible round green bean and grows in a pod on a leguminous vine. Dried peas are often used in soup or eaten on their own (Wikipedia 2006). Pea is one of the common food plants in Turkey grown for fresh consumption and is a raw material of the canned food industry. It is grown on 1350 ha in Turkey with a production rate of 3500 t/year (SIS 2004). The black-eyed pea (Vigna sinensis L.) is a subspecies of the cowpea, grown for its mediumsized edible grain, and mutates easily giving rise to a number of varieties in Turkey. Native to Africa, it is widely grown in Africa and Asia and is still grown for food in many countries. Black-eyed peas are excellent sources of calcium, folate, and Vitamin A (Wikipedia 2006). It is one of the common food plants in coastal areas of Turkey grown for fresh consumption and is a raw material of the canned food industry. Black-eyed pea is grown on 2900 ha in Turkey with a production rate of 2300 t/year (SIS 2004). Information on the physical properties of legume seeds such as size dimensions, shapes, porosity, volume, density, and coefficient of friction is important in the design of harvesting, transporting, cleaning, separating, packing, storing, and processing equipment. Bulk density and porosity affect the structural loads. The coefficient of friction of seeds against various surfaces is also necessary in the design of conveying, transporting, and storing structures.

3 424 new Zealand Journal of Crop and Horticultural science, 2007, Vol. 35 The coefficient of friction between seed and wall is an important parameter in the prediction of seed pressure on walls. The coefficient of static friction also plays an important role in transporting (load and unload) of goods and design of storage facilities. the effect of moisture content on the physical properties of chickpea seeds (konak et al. 2002), QP-38 pigeon pea (baryeh & mangope 2002), cocoa bean (bart- Plange & baryeh 2003), lentil seed (Amin et al. 2004), and faba bean (Altuntas & Yildiz 2007) have been reported. several researchers have also determined the agronomic, mechanical, and thermal properties of grain legume seeds (bay et al. 1996; Fasina et al. 2001; Akinjayeju & bisiriyu 2004; bhattacharya et al. 2005). However, studies conducted on the effect of moisture content on grain legume seeds such as kidney bean, pea, and black-eyed pea seeds have not been adequately or comparatively studied. the objective of this study was to investigate the physical properties of some grain legumes such as kidney bean, pea, and black-eyed pea seeds as a function of the moisture content. MATERIALS AND METHODS Dry mature kidney bean, pea, and black-eyed pea grains were used in the experiments. the grain legume seeds used were obtained from the production year of 2005, and purchased from the producers. kidney bean ('Barbunia') and black-eyed pea ('Karnikara') are native populations, and pea ('Rona') is a commercial variety in Turkey. Black-eyed pea is classified based on the colour of hilum in turkish standards, ts 3268 (tse 1978). the samples were manually cleaned to remove foreign matter, dust, dirt, broken and immature grains. the initial moisture content of the samples was determined using the standard hot-air oven method at 105 ± 1 C for 24h (brusewitz 1975; suthar & Das 1996). the seeds at desired moisture levels were prepared by adding calculated amounts of distilled water, through mixing and sealing in separate polyethylene bags. t h e samples were kept at low temperature (5 C) in a refrigerator for 7 days to obtain uniform moisture distribution throughout the samples. the required quantities of the samples were taken out of the refrigerator, and allowed to warm up at room temperature for c. 2 h. the wetting technique used to obtain the desired moisture content has frequently been reported (Deshpande et al. 1993; Visvanathan et al. 1996; Gupta & Das 1997; nimkar & Chattopadhyay 2001; sacilik et al. 2003). t h e moisture contents were calculated from the following equation (balasubramanian 2001; sacilik et al. 2003): [ ()100 Mf where Q is the mass of water added in kg, Wi is the initial mass of a sample in kg, M i is the initial moisture content of a sample in % wet basis, and Mf is the final moisture content of the sample in % wet basis. the physical properties of the grain legume seeds were determined at three moisture levels in the range % (wet basis) and %, and % for kidney bean, pea, and black-eyed pea seeds, respectively (table 1). the measurement of physical property at each moisture content was replicated 10 times. the length, width, thickness, and weight of grain legume seeds at each moisture content were measured in 100 randomly selected legume seeds using a dial-micrometer (kafer si 112) to an accuracy of 0.01 g. the geometric mean diameter (D g ) and sphericity (Φ) of grain legumes were calculated using the following relationships (mohsenin 1970): D g = (lwt) 1/3 ()LWT1 13 T 100 (1) (2) where L is the length, W is the width, and T is the thickness in mm. Table 1 study. moisture content levels (%wetbasis)ofgrain fc l grain e legume seeds in this Grain legumes Mel moisture content (%) mc2 m c 3 kidney bean (Phaselous vulgaris) Pea (Pisum sativum) black-eyed pea (Vigna sinensis)

4 Altuntas & Demirtola Effect of moisture content 425 the unit mass of the seed and thousand-seed (1000-seed) weight were measured with a digital electronic balance (shinko AF-r-220) at an accuracy of g (Çarman 1996; sacilik et al. 2003). the weights of 10 samples representing each of the moisture contents and containing 100 randomly selected seeds were averaged to evaluate 1000-seed mass (Öğüt 1998). the grain legume seeds were placed on a paper, and the boundary lines were traced. the projected area was measured by a digital planimeter (Placom roller-type, kp90n) (sirisomboon et al. 2007). kp90n has a computing function that gives the measurement readout in the scale desired (sq.ft., acres). Features include an easy roller operation that simply follows the outline of the area to be measured and the reading on the digital display corresponds to the circumscribed area. (specifications: max. measuring range, 325 mm vertical, 30 m horizontal; accuracy, within ±0.2% (within ±2/1000 pulses).) The kernel density of a grain is defined as the ratio of the mass of legume seed and the kernel volume of the seed that is determined by the toluene (C 7 H 8 ) displacement method. toluene was used in place of water because it is absorbed by the seeds to a lesser extent. the volume of toluene displaced was found by immersing a weighted quantity of legume seed in the toluene (sitkei 1976; mohsenin 1970; sacilik et al. 2003). the bulk density is the ratio of a sample mass of a seed to its total volume. bulk density was determined using the standard test weight procedure (singh & Goswami 1996), filling a container of 500 ml with the seed from a height of 150 mm at a constant rate and weighing the content (Özarslan 2002). the porosity (ε) was determined by the following equation: : = l- ê. xloo P*. (3) where ρ b and ρ t are the bulk and kernel densities, respectively (mohsenin 1970). the angle of repose is the angle with the horizontal at which the material stands when piled. this was determined using a topless and bottomless cylinder of 300 mm diameter and 500 mm height. t h e cylinder was placed at the centre of a raised circular plate and filled with grain legume seeds. The cylinder was slowly raised until forming a cone on a circular plate. the angle of repose was calculated from the measurement of the height and diameter of the cone (kaleemullah & Gunasekar 2002). Fig. 1 force. Travel direction Normal force Sample Friction surface schematic of the measuring device for friction The coefficient of friction of grain legume seeds was measured by a friction device. the measuring device of friction force is formed by a metal box, a friction surface, and an electronic unit, which covers the mechanical force unit, electronic variator, loadcell, electronic ADC (Analog digital converter) card, and PC (personel computer) (kara et al. 1997; kasap & Altuntas 2006). Friction forces were measured by the loadcell, converted by the ADC card, and data were recorded in a computer. A schematic of the measuring device of friction force is shown in Fig. 1. the static and dynamic coefficients of friction were calculated using the following equation: N (4) where, µ is the coefficient of friction, F is the measured friction in N, and Nf is the normal force in N. the maximum value of friction force was obtained when the box started moving, and this was used to calculate the static coefficients of friction. While the box continued to slide over the friction surface at 0.02 m/s velocity, the dynamic coefficients of friction were measured. the average value of coefficient of friction was used to calculate the dynamic coefficients of friction. The experiment was conducted at different moisture contents of grain legume seed using friction surfaces of galvanised metal, chipboard, mild steel, plywood, and rubber. For each experiment, the sample box was emptied and refilled with a different sample at the same moisture content (sacilik et al. 2003). statistical analyses were conducted with microsoft Excel and spss 10.0 software (spss 2000). results from the experiments were analysed based on a randomised complete block design with split plot.

5 426 new Zealand Journal of Crop and Horticultural science, 2007, Vol. 35 RESULTS AND DISCUSSION Grain size About 83% of the kidney bean seeds have a length range of mm, c. 70% have a width range of mm, c. 78% have a thickness range of mm, and c. 86 % a seed mass range of g at 8.21% moisture content. For pea seeds, c. 78% have a length range of mm, c. 85% have a width range of mm, c. 78% have a thickness range of mm, and c. 75% have a seed mass range of g at 8.20% moisture content on a dry basis. About 88% have a length range of mm, c. 82% have a width range of mm, c. 76% have a thickness range of mm and c. 84% have a seed mass range of g at 5.66% moisture content for black-eyed pea seeds (Fig. 2). the average length, width, thickness, geometric mean diameter, and unit mass of kidney bean seed range was mm, mm, mm, mm, and g as the moisture content increased from 8.21 to 18.01% wet basis, respectively. the average length, width, thickness, geometric mean diameter, and unit mass of pea seeds range was mm, mm, mm, mm, g, as moisture content increased from 8.20% to 14.56% wet basis, respectively. the average length, width and thickness, geometric mean diameter, and unit mass of the black-eyed pea seeds varied from 9.19 to 9.47 mm, 6.96 to 7.19mm, 6.26 to 6.47 mm, 7.32 to 7.59mm, and to 0.273g, respectively as moisture content increased from 5.66% to % wet basis (tables 2, 3, and 4). Sphericity t h e sphericity of some grain legumes were calculated with Equation 2 using the data on the geometric mean diameter of the grain legume seeds. the results obtained are presented in tables 2, 3, and 4. As the moisture content increased from 8.21% to 18.01%, average sphericity increased from 61.03% to 61.31% for kidney bean seeds. the sphericity of the pea and black-eyed pea seeds increased from 78.51% to 79.12% and 79.72% to 80.21% as the moisture content increased from 8.20% to 14.56%, and 5.66% to 13.25%, respectively. the effects of variety and moisture content on sphericity were not significant for grain legumes investigated. the relationship between moisture content (mc) and sphericity (Φ) was represented by the following equations: O (kidney bean ) = m c (R 2 = 0.829) (5) O (pea) = m c (R 2 = 1.00) (6) O (black-eyed pea) = mc (R 2 = 0.896)(7) similar trends have also been reported by Desphande et al. (1993) for soybean seed, nimkar & Chattopadhyay (2001) for green gram, Aydin et al. (2002) for turkish mahaleb, and Özarslan (2002) for cotton seeds, respectively. Thousand-seed mass the 1000-seed mass of grain legumes (m1000) linearly increased from to g for kidney bean grains as the moisture content increased from 8.21 % to 18.01%. the m 1000 range was g forpea seeds as the moisture content increased from 8.20% to 14.56%. similarly, m 1000 range was g for black-eyed pea seeds as moisture content increased from 5.66% to 13.25% (tables 2,3, and 4). the m 1000 generally increased as moisture content increased for each grain legume seed. the effect of moisture content on 1000-grain weight of grain legumes seeds was statistically significant (P < 0.05). this relationship between moisture content (m c ) and thousand grain mass (m1000 ) was described by the following regression equations: m 1000 (kidney bean) = m c (R 2 = 0.946) (8) m (pea) = mc (R 2 = 0.772) (9) m 1000 (black-eyed pea) = mc (R 2 =0.846) (10) the positive linear relationship of 1000-seed mass and moisture content were also reported by Aviara et al. (1999) and Vilche et al. (2003) for guna seeds and quinoa seeds, respectively. Projected area the projected area of kidney bean seeds linearly increased from 1.24 to 1.52 cm 2 as the moisture content increased from 8.21% to 18.01%. the projected area of pea seed linearly increased from 0.37 to 0.51 cm 2 with increasing the moisture content of pea seed from 8.20% to 14.56%. the projected area of black-eyed pea seed linearly increased from 0.58 to 0.73 cm 2, with increase in moisture content from 5.66% to 13.25%, respectively (tables 2,3, and 4). Projected area generally increased as moisture content increased for three grain legume seeds. the effect of moisture content on projected area of kidney bean, pea, and black-eyed seeds was not statistically significant. the relationships between moisture content (m c ) and projectied area (A p ) for kidney bean, pea,

6 Altuntas & Demirtola Effect of moisture content M, g 0,17-0,29 0,29-0,40 0,40-0,52 0,52-0,63 T, mm 4, ,23-5,84 5,84-6,45 6,45-7,05 W, mm 7,06-7,51 7,51-7,96 7,96-8, ,85 L, mm 11,25-12,46 12,46-13,68 13,68-14,89 14,89-16,11 Seed dimension M, g 0,091-0,112 0,112-0,133 0,133-0,155 0,155-0,176 T, mm 3,31-3,60 3,60-3,88 3,88-4,17 4,17-4,46 W, mm 5,19-5,58 5,58-5,97 5,97-6,37 6,37-6,76 L, mm 6, ,53-6,87 6,87-7,21 7,21-7,54 Size dimension 0,63-0,75 0,75-0,86 0,86-0,88 7,05-7,66 7,66-8,27 8,27-8,88 8,85-9,29 9,29-9,74 9,74-10,19 16,11-17,32 17,32-18,54 18,54-19,75 0,176-0,198 0,198-0,219 0,219-0,240 4, ,74-5,03 5,03-5,31 6,76-7,15 7,15-7,54 7,54-7,94 7,54-7,88 7,88-8,22 8,22-8,56 0, ,163-0,208 4,81-5,22 5,22-5,63 5,44-5,83 5,83-6,22 5,25-6,32 6,32-7,39 0,208-0,253 0,253-0,297 5,63-6,04 6,04-6, ,62 6,62-7,01 7, ,54 Size dimension 0,297-0,342 0,342-0,387 0,387-0,431 6,46-6,87 6,87-7, , , ,19 9,54-10,61 10,61-11,68 11,68-12,75 Fig. 2 Frequency distribution curves of some grain legume seeds length, width, thickness, and unit seed mass.

7 428 new Zealand Journal of Crop and Horticultural science, 2007, Vol. 35 Table 2 Descriptive statististics for kidney bean (Phaselous vulgaris) at varying moisture contents. Physical properties length (mm) Width (mm) thickness (mm) Geometric mean diam. (mm) unit seed mass (g) sphericity (%) 1000-seed mass (g) Projected area (cm 2 ) bulk density (kg/m 3 ) kernel density (kg/m 3 ) Porosity (%) seed volume (cm 3 ) Angle of repose ( ) Table 3 Physical properties moisture content (% wet basis) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.15 Descriptive statististics for pea (Pisum sativum) at varying moisture content. length (mm) Width (mm) thickness (mm) Geometric mean diam. (mm) unit seed mass (g) sphericity (%) 1000-seed mass (g) Projected area (cm 2 ) bulk density (kg/m 3 ) kernel density (kg/m 3 ) Porosity (%) seed volume (cm 3 ) Angle of repose ( ) Table ± ± ± ± ± ± ± ± ± ± ± ± ± 0.45 moisture content (% wet basis) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.16 Descriptive statististics for black-eyed pea (Vigna sinensis) at varying moisture contents. Physical properties length (mm) Width (mm) thickness (mm) Geometric mean diam. (mm) unit seed mass (g) sphericity (%) 1000-seed mass (g) Projected area (cm 2 ) bulk density (kg/m 3 ) kernel density (kg/m 3 ) Porosity (%) seed volume (cm 3 ) Angle of repose ( ) moisture content (% wet basis) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.46

8 Altuntas & Demirtola Effect of moisture content 429 and black-eyed pea seeds were described by the following equations: A p (kidney bean) = m c (R 2 = 0.988) (11) A p (pea) = mc (R 2 = 0.982) (12) Ap (black-eyed bean) = mc (R 2 = 0.993) (13) similar trends have been reported by Desphande et al. (1993) for soybean, Çarman (1996) for lentil, Öğüt (1998) for white lupin, Aydin et al. (2002) for turkish mahaleb, baryeh (2002) for millet, konak et al. (2002) for chickpea, Özarslan (2002) for cotton, saciliketal. (2003) for hemp seed, Calisiretal. (2005) for safflower, Aydin (2006) for peanut, and Altuntaş & Yildiz (2007) for faba bean grains, respectively. Bulk and kernel densities the bulk density for the three legume seeds was presented in tables 2, 3, and 4. bulk density of seeds generally decreased for three grain legumes as moisture content increased. the bulk density for pea was higher than that of kidney beans and black-eyed peas. the decrease in bulk density of legume seeds would be owing to an increase in size with moisture content, which gives rise to a decrease in the quantity of seeds occupying the same bulk volume (sahoo & srivastava 2002; sacilik et al. 2003). t h e effect of moisture content on kernel density of grain legume seeds showed a decrease with increasing moisture content. similarly, kernel densities for pea were higher than those of kidney bean and blackeyed peas. the kernel density of seeds generally decreased as the moisture content increased for kidney bean, pea, and black-eyed pea seeds. this was owing to the higher rate of increase in single seed volume for grain legume seeds compared to single seed weight for grain legume seeds (sahoo & srivastava 2002). the effects of moisture content on bulk and kernel densities for grain legume seeds were statistically significant (P < 0.01). the relationships between moisture content (m c ) and bulk density (ρ b ) and kernel density (ρ t ) were linear as described by the following equations: ρ b (kidney bean) = m c (R 2 = 0.995)(14) ρ t (kidney bean) = m c (R 2 = 0.980)(15) ρ b (pea) = m c (R 2 = 0.884) (16) ρ t (pea) = mc (R 2 = 0.998) (17) ρ b (black-eyed pea) = mc (R 2 = 0.997) (18) ρ t (black-eyed pea) = m c (R 2 = 0.998)(19) the negative linear relationships between bulk and kernel densities and moisture content have been reported by Desphande et al. (1993) for soybean, Aviara et al. (1999) for guna seed, Aydin et al. (2002) for turkish mahaleb, kaleemullah & Gunasekar (2002) for arecanut seed, konak et al. (2002) for chickpea, Özarslan (2002) for cotton seed, baryeh & mangope (2003) for pigeon pea, sacilik et al. (2003) for hemp seed, Aydin (2006) for peanut, and Altuntaş & Yildiz (2007) for faba bean grains, respectively. Porosity Porosity was calculated by applying Equation 3 to bulk and kernel density data for the three legume seeds. the results obtained for porosity of the legume seeds are presented in tables 2,3, and 4. the porosity of kidney beans and pea seeds increased and the porosity of black-eyed peas decreased with an increase in moisture content. the effect of moisture content on porosity for each grain legume seed was not significant. This relationship between moisture content (m c ) and porosity (ε) was described by the following regression equations: e (kidney bean) = m c (R 2 = 0.996) (20) e (pea) = m c (R 2 = 0.744) (21) e (black-eyed pea) = m c (R 2 = 0.908) (22) similar results were also reported by Desphande et al. (1993) for soybean, Joshi et al. (1993) for pumpkin seed, balasubramanian (2001) for raw cashew nut, nimkar & Chattopadhyay (2001) for green gram, sahoo & srivastava (2002) for okra seed, and konak et al. (2002) for chickpea seeds, respectively. Volume of seed the volume of seed calculated using the data on unit mass of the seed and kernel density of the grain legume seeds, and the results obtained are presented in tables 2, 3 and 4. As the moisture content increased, the average seed volume of kidney beans, black-eyed pea, and peas also increased. As expected, the values for kidney bean seeds were higher than those for pea and black-eyed pea seeds. the effect of moisture content on seed volume of kidney bean and pea seeds was significant (P < 0.05 and P < 0.01), whereas the effect of moisture content on seed volume of black-eyed pea seed was not statistically significant. the relationships between moisture content (m c ) and seed volume (V) for kidney bean, pea, and black-eyed pea seeds were described by the following equations:

9 430 new Zealand Journal of Crop and Horticultural science, 2007, Vol. 35.Q ] x Galvanized metal -Chipboard -Rubber Moisture content (%) Moisture content (%) Moisture content (%) o 0.3 y CO ! Moisture content (%) Moisture content (%) Moisture content (%) Fig. 3 Static and dynamic coefficients of friction on various friction surfaces for kidney bean (Phaselous vulgaris), pea (Pisum sativum), and black-eyed pea (Vigna sinensis) seeds at varying moisture contents. A, kidney bean (8.21% wet basis); B, pea (8.20% wet basis); C, black-eyed pea (5.66% wet basis) V(kidney bean) = m c (R 2 = 0.997) (23) V (pea) = mc (R 2 = 0.996) (24) V (black-eyed pea) = m c (R 2 = 0.964)(25) similar trends of increase have been reported by Desphande et al. (1993) for soybean, Öğüt (1998) for white lupin, Aviara et al. (1999) for guna seed, baryeh (2002) for millet, Özarslan (2002) for cotton seed, sahoo & srivastava (2002) for okra seed, sacilik et al. (2003) for hemp seed, Aydin (2006) for peanut, and Altuntas & Yildiz (2007) for faba bean grains, respectively. Angle of repose the experimental results for angle of repose for kidney bean, pea, and black-eyed pea seeds with respect to moisture content are shown in tables 2, 3, and 4. A linear increase was observed with increasing moisture content for all legume seeds. the effect of moisture content on angle of repose for grain legumes seeds was significant (P < 0.01). the relationships between moisture content (m c ) and angle of repose (Ξ) were represented by the following repression equations: 5 (kidney bean) = mc (R 2 = 0.829) (26)

10 Altuntas & Demirtola Effect of moisture content (pea) = m c (R 2 = 0.966) (27) 5 (black-eyed pea) = mc (R 2 = 1.00) (28) these results were similar to those reported by Joshi et al. (1993) for pumpkin seed, Gupta & Das (1997) for sunflower seed, Aviara et al. (1999) for guna seed, nimkar & Chattopadhyay (2001) for green gram, kaleemullah & Gunasekar (2002) for arecanut seed, irtwange & igbeka (2002) for two african yam beans, Aydin et al. (2002) for turkish mahaleb, baryeh (2002) for millet, konak et al. (2002) for chickpea seed, baryeh & mangope (2003) for pigeon pea, and sacilik et al. (2003) for hemp seeds, respectively. Static and dynamic coefficient of friction Results from the static and dynamic coefficients of friction on various surfaces, namely, galvanised metal, chipboard, mild steel, plywood, and rubber surfaces on some grain legume seeds were compared (see Fig. 3). The static coefficients of friction at any moisture content was higher than that of the dynamic coefficients of friction. The static and dynamic coefficients of friction linearly increased with moisture content for all five surfaces. the linear equations for both static and dynamic coefficients of friction on all three surfaces could be described as: µ=a + BM c (29) Table 5 Regression coefficients and coefficients determination of Equation 29 for static and dynamic coefficients of friction on various friction surfaces. Grain legumes Kidney bean (Phaselous vulgaris) Static coefficient of friction Dynamic coefficient of friction Pea (Pisum sativum) Static coefficient of friction Dynamic coefficient of friction Black-eyed pea (Vigna sinensis) Static coefficient of friction Dynamic coefficient of friction surface Galvanised metal Chipboard mild metal Plywood rubber Galvanised metal Chipboard mild metal Plywood rubber Galvanised metal Chipboard mild metal Plywood rubber Galvanised metal Chipboard mild metal Plywood rubber Galvanised metal Chipboard mild metal Plywood rubber Galvanised metal Chipboard mild metal Plywood rubber Regression coefficient intercept (A) slope (b) Coefficient of determination (R 2 )

11 432 New Zealand Journal of Crop and Horticultural Science, 2007, Vol. 35 where, ]Á is the coefficient of friction and A and B are regression coefficients. The corresponding values are shown in Table 5. The static and dynamic coefficients of friction were the greatest at rubber followed by at plywood, mild metal, chipboard, and at galvanised metal at all moisture contents studied. This would be because galvanised metal is smoother than the other surfaces (Gupta & Das 1997; Sacilik et al. 2003; Altuntas et al. 2005). At higher moisture contents, the seed became rougher, and thus sliding was diminished. The roughness also decreased with an increase in seed moisture content (Sahoo & Srivastava 2002). As the moisture content of the seed increased, the static and dynamic coefficients significantly increased. This is a result of the increasing adhesion between the product and the surface at higher moisture content (Nimkar & Chattopadhyay 2001; Konak et al. 2002; Özarslan 2002). The effects of moisture content and friction surfaces on static and dynamic coefficients of friction were significant (P < 0.01). Similar results were found by others (Carman 1996; Suthar & Das 1996; Visvanathan et al. 1996; Baryeh 2002; Özarslan 2002). CONCLUSION Some physical properties for some grain legume seeds such as kidney bean, pea, and black-eyed pea seeds were evaluated in a moisture content range. In each grain legume seed, size dimension, sphericity, 1000-seed mass, and projected area increased as moisture content increased. The bulk and kernel densities decreased as moisture content increased. In the moisture content range studied, porosity, seed volume, and angle of repose increased for each grain legume seed. The static and dynamic coefficients of friction on various surfaces linearly increased with increasing the moisture content for each grain legume seed. The static and dynamic coefficients of friction were maximum for rubber followed by plywood, mild metal, and chipboard, and minimum for galvanised metal at all moisture contents studied. The effects of moisture content on sphericity, 1000-seed mass, bulk and kernel densities, volume of seed, angle of repose, and the static and dynamic coefficients of friction on various surfaces were significant, whereas on projected area and porosity they were not statistically significant. ACKNOWLEDGMENTS We are grateful to Dr Hikmet Gunal for critical reading and correcting the English. REFERENCES Altuntas E, Özgöz E, Taser ÖF Some physical properties of fenugreek (Trigonella foenumgraceum L.) seeds. Journal of Food Engineering 71: Altuntas. E, Yildiz M Effect of moisture content on some physical and mechanical properties of faba bean (Vicia faba L.) grains. Journal of Food Engineering 78: Akinjayeju O, Bisiriyu KT Comparative studies of some properties of undehulled mechanically dehulled and manually dehulled cowpea (Vigna unguiculata Walp. L.) flours. International Journal of Food Science and Technology 39: Amin MN, Hossain MA, Roy KC 2004 Effects of moisture content on some physical properties of lentil seeds. Journal of Food Engineering 65: Aviara NA, Gwandzang MI, Haque MA Physical properties of guna seeds. Journal of Agricultural Engineering Research 73: Aydin C Some engineering properties of peanut and kernel. Journal of Food Engineering 79: Aydin C, Ögüt H, Konak M Some physical properties of Turkish Mahaleb. Biosystem Engineering 82: Balasubramanian D Physical properties of raw cashew nut. Journal of Agricultural Engineering Research 78: Bart-Plange A, Baryeh EA The physical properties of Category B cocoa beans. Journal of Food Engineering 60: Baryeh EA Physical properties of millet. Journal of Food Engineering 51: Baryeh EA, Mangope BK Some physical properties of QP-38 variety pigeon pea. Journal of Food Engineering 56: Bay APM, Bourne MC, Taylor AG Effect of moisture content on compressive strength of whole snap bean (Phaseolus vulgaris L.) seeds and separated cotyledons. International Journal of Food Science & Technology 31: Bhattacarya S, Narasimha HV, Bhattacharya S The moisture dependent physical and mechanical properties of whole lentil pulse and split cotyledon. International Journal of Food Science and Technology 40: Brusetwitz GH Density of rewetted high moisture grains. Transaction of the ASAE 18:

12 Altuntas & Demirtola Effect of moisture content 433 Calisir S, Marakoglu T, Ozturk O, Öğüt H Some physical properties of safflower seed (Carthamus Tinctorius L.). Journal of the Agricultural Faculty of Selcuk University 19: Çarman K Some physical properties of lentil seeds. Journal of Agricultural Engineering Research 63: Deshpande SD, Bal S, Ojha, TP Physical properties of soybean seeds. Journal of Agricultural Engineering Research 56: FAO Statistical database, [accessed 12 November 2006]. Fasina O, Tyler B, Pickard M, Zheng G, Wang N Effect of infrared heating on the properties of legume seeds. International Journal of Food Science & Technology 36: Gupta RK, Das SK Physical properties of sunflower seeds. Journal of Agricultural Engineering Research 66: 1-8. Irtwange SV, Igbeka JC Selected moisture dedendent friction properties of two African yam bean (Sphenostylis stenocarpa) accessions. American Society of Agricultural Engineers 18: Joshi DC, Das SK, Mukherjee RK Physical properties of pumpkin seeds. Journal of Agricultural Engineering Research 54: Kaleemullah S, Gunasekar JJ Moisture-dependent physical properties of arecanut trues. Biosystem Engineering 82: Kara M, Turgut N, Erkmen Y, Güler İE Determination of coefficient of friction of some granules. In: 17th National Symposium on Mechanization in Agriculture, Tokat, Turkey. Pp (In Turkish with abstract in English.) Kasap A, Altuntas, E Physical properties of monogerm sugarbeet (Beta vulgaris var. altissima) seeds. New Zealand Journal of Crop and Horticultural Science 34: Konak M, Çarman K, Aydin C Physical properties of chickpea seeds. Biosystems Engineering 82: Mohsenin NN Physical properties of plant and animal materials. New York, Gordon & Breach Science Publishers. Nimkar PM, Chattopadhyay PK Some physical properties of green gram. Journal of Agricultural Engineering Research 80: Öğüt H Some physical propetrites of white lupin. Journal of Agricultural Engineering Research 69: Özarslan C Some physical properties of cotton seed. Biosystems Engineering 83: Sacilik K, Öztürk R, Keskin R Some physical properties of hemp seed. Biosystems Engineering 86: Sahoo PK, Srivastava AP Physical properties of okra seed. Biosystems Engineering 83: Singh KK, Goswami, KK Physical properties of cumin seed. Journal of Agricultural Engineering Research 64: Sirisomboon P, Pornchaloempong P, Romphophak T Physical properties of green soybean: criteria for sorting. Journal of Food Engineering 79: SIS Agricultural structure. State Instate of Statistics, Printing Division, Ankara, Turkey. Sitkei G Mechanic of agricultural materials. Budapest, Akademia Kiado. SPSS SPSS for Windows. Student version. Release Spss Inc /L United States. Suthar SH, Das SK, Some physical properties of karingda (Citrus lanatus (thumb) mansf) seeds. Journal of Agricultural Engineering Research 65: TSE Dry cowpeas. standard/standardlar.asp.ts 3268 [accessed 22 May 2007]. Vilche C, Gely M, Santalla E Physical properties of quinoa seeds. Biosystems Engineering 86: Visvanathan R, Palanisamy PT, Gothandapani L, Sreenarayanan VV Physical properties of neem nut. Journal of Agricultural Engineering Research 63: Walton The legumes, [accessed 10 October 2006]. Wikipedia Bean. The free encyclopedia, en.wikipedia.org [accessed 10 October 2006]. World's Healthiest Foods 2006 Kidney beans, whfoods.com [accessed 20 October 2006].