Some Engineering Properties of Sunflower Seed and Its Kernel

Aug. 2010, Volume 4, No.4 (Serial No.29) Journal of Agricultural Science and Technology, ISSN 1939-1250, USA Some Engineering Properties of Sunflower Seed and Its Kernel R. Khodabakhshian, B. Emadi and M. H. Abbaspour Fard Agricultural Machinery Department, Ferdowsi University of Mashhad, Mashhad 91775-1163, Iran Received: September 22, 2009 / Accepted: November 14, 2009 / Published: August 15, 2010. Abstract: Some engineering properties of sunflower seed and its kernel, Shahroodi variety as a case study, were investigated at various moisture content levels (3-14% d.b.) for three size categories (large, medium and small). With increase of moisture content from 3 to 14% d.b., all the main dimensions (length, width and thickness), geometric mean diameter, porosity, true density, terminal velocity and static coefficient of friction increased while bulk density and rupture force for both sunflower seed and its kernel decreased for all size categories. The results showed that the highest value of static coefficient of friction for both seed and kernel was on the rubber surface, followed by plywood, polyethylene, galvanized iron, and finally aluminium surfaces. The seeds required less compressive force to dehull when loaded under the horizontal as compared to the vertical orientation. But for kernels, the trend was the opposite. Also, the compressive forces needed to initiate rupture of sunflower seed hulls were higher (47.1-94.72 N) than those required to rupture the kernel (8.5-13.4 N) in both orientations. Key words: Sunflower seed, kernel, engineering properties, Shahroodi variety, moisture content, size. 1. Introduction Sunflower (Helianthus annuus L.) seed is considered to be an important oilseed crop because it contains in large quantity highly nutritious oil [1]. The hull, which comprises between 20% and 30% of the seed, depending on the variety, contains mostly crude fibre and an insignificant quantity of fat [2]. According to Iranian government statistical data of 2005, over 35 varieties of sunflower are cultivated in Iran. The produce of sunflower seed is used for oil production and fresh consumption with the ratio of 90% and 10%, respectively. Information on engineering properties of sunflower seed/kernel and their dependency on operational parameters are useful for the design of various processing equipment such as cleaner, grader, dehuller, separator and oil expeller. The major moisture-dependent engineering properties of biological materials are shape and size, Corresponding author: R. Khodabakhshian, Master, research fields: postharvest technology, design of farm machinery and maintenance. E-mail: ra_kh544@stu-mail.um.ac.ir. bulk density, true density, porosity, friction against various surfaces and rupture force. For instance, the size and shape of seeds are important for either their electrostatic separation from undesirable materials [3]. Also, the identification of seed shape could be important for an analytical prediction of its drying behavior [4]. Bulk density, true density and porosity are useful in sizing grain hoppers and storage facilities as they can affect the rate of heat and mass transfer during aeration and drying operations [5]. Wu et al. [6] reported the importance of difference in size and density during separating particles by segregating on gravity tables. The static coefficient of friction is used to determine the angle at which chutes must be positioned in order to achieve consistent flow of materials through the chute. Such information is useful in sizing motor requirements for grain transportation and handling [7]. When grains are submitted to forces that exceed the resistance of the material, grain breakage or cracks are found [8]. These properties have been studied for various crops such as oilbean [9],

38 Some Engineering Properties of Sunflower Seed and Its Kernel soybean [10], Pumpkin seed [11], wheat [12], lentil [13], sunflower seed [14], green gram [15], cotton [16], sorghum seeds [17], chick pea seeds [18], safflower seeds [19] and cumin seed [20]. The object of this study was to investigate some engineering properties of sunflower seed and its kernel, namely axial dimensions, sphericity, true and bulk densities, porosity, terminal velocity, static coefficient of friction on five structural surfaces and rupture force as a function of size and moisture content in the range of 3% to 14% (d.b.). 2. Materials and Methods 2.1 Sample Preparation For this study, Shahroodi variety was obtained from a region of Khorasan Razavi Province, Iran, during autumn season in 2008. A portion of seeds equal to twenty kilograms were selected and transported to technical and engineering research centre in Khorasan Razavi Province. The seeds were manually cleaned to remove all foreign matters such as dust, dirt, stones, immature and broken seeds. To get whole kernels, the seeds were manually dehulled. Then, the initial moisture content of seed was determined 7.9% d.b. using the standard hot air oven method with a temperature setting of 105±1 for 24 h [14, 21, 22]. Also, in the similar way, the initial moisture content of kernel was 5.9% d.b.. To investigate the effect of seed / kernel size on engineering properties, the seeds were graded into three size categories (small, medium and large) using 5.5, 6.5 and 8 mesh sieves. All the engineering properties were measured for three moisture contents in the range of 3 to 14% (d.b.) that is a usual range since harvesting, transportation, storage and processing operations of sunflower seed. To get the seeds and kernels with the desired moisture content, sub-samples of seeds and kernels of each size category (small, medium and large), each weighing 0.5 kg, were drawn from the bulk sample and dried (by putting them in the oven at 75 for 2 h) or adding calculated quantity of water. The quantity of water which should be added to the seed and kernel was determined using the following equation [22]: Wi ( M f Mi ) Q = 100 M (1) f where Q is the mass of water added, kg, W i is the initial mass of the sample in kg, M i is the initial moisture content of the sample in d.b.% and M f is the final moisture content of the sample in d.b.%. Then, pre-determined quantity of water was added to the sub-samples and they were kept in double-layered low-density polyethylene bags of 90 µm thickness, sealed and stored at low temperature (5 in a refrigerator) to avoid the growth of microorganisms and to allow uniformity of moisture distribution. Before starting the tests, the required quantities of seeds and kernels were taken out of the refrigerator and allowed to warm with room temperature for approximately 2 h [11, 14]. To determine the size and shape of seed and kernel for revealing the relations of length, width and thickness, totally 50 seeds and kernels of each sub-sample were randomly selected and labeled for easy identification. This method of random sampling was similar to Baryeh [23], Erica et al. [24] and Saiedirad et al. [20]. Finally, three main dimensions namely length, width and thickness for both seed and kernel were carefully measured using a digital caliper (Diamond, China) with an accuracy of ±0.02 mm. The average of seed and kernel diameter was computed using geometric mean, The geometric mean diameter, Dg, was calculated using the following equation [3]: 1/3 D g = (LWT ) (2) Where L is the length, W is width and T is the thickness. The criterion used to describe the shape of sunflower seed and its kernel was sphericity. The sphericity, φ, of seed and kernel was determined using the following formula [3]: ( LDT ) 1/ 3 ϕ = (3) L The true volume (V, cm³) of seeds and kernels as a

Some Engineering Properties of Sunflower Seed and Its Kernel 39 function of variety, size and moisture content were determined using the toluene (C 7 H 8 ) displacement method [25]. Toluene was used in place of water because it is absorbed by seed and kernel of sunflower to a lesser extent. Furthermore, its surface tension is low, so that it fills even shallow dips in a seed and its dissolution power is also low [26]. The true density of a seed or a kernel (ρ t, kg m -3 ) is defined as the ratio of its mass to its actual volume and hence was calculated by dividing the unit mass of each sample (seed or kernel) to its true volume [27]. The bulk density of particulate materials (ρ b, kg m -3 ) is the ratio of the sample mass to its total volume. This was determined by filling a cylindrical container of 500 ml volume with seeds (kernels) to a height of 15 cm at a constant rate and then weighting the contents. This method has also been employed by others [14, 28, 29]. Thompson and Isaac [30] described the porosity (ε) as the fractions of the space in the bulk grain that is not occupied by the grain. Accordingly, Mohsenin [3] calculated the porosity as follow: ρ ε = 1 b 100 (4) ρ t The terminal velocity (V t ) of seed and kernel at different moisture content and size category was measured using an air column. The static coefficient of friction, µ, was measured on five structural surfaces: aluminium, plywood, galvanized iron, polyethylene and rubber. An open-ended galvanized iron cylinder, 100 mm diameter and 50 mm height, was filled with the sample of the desired moisture content and placed on the adjustable tilting surface so that the cylinder dose not touch the surface. The tilting surface with the cylinder resting on it was raised gradually with a screw device until the cylinder just starts to slide down and the angle of tilt (α) was read from a scale [14-27]. The coefficient of friction (µ) was calculated from the following relationship [3]: µ=tan α (5) An Instron Universal Testing Machine (Model QTS 25) equipped with a 25 kg load cell and integrator was used for the compression of the sunflower seed and its kernel [20]. The measurement accuracy was ±0.001 N in force and 0.001 mm in deformation. Each individual seed or kernel was loaded between two parallel plates of the machine compressed at the preset condition until rupture occurred as is denoted by a bio-yield point in the force-deformation curve. A typical forcedeformation curve is shown in Fig. 1. As soon as the bio-yield point was detected, the loading was stopped. At a fixed crosshead speed of 2 mm/min, 18 series of tests (moisture content in three levels: 3%, 7% and 14%, size category in three levels: small, medium and large; and loading orientation in two levels: horizontal and vertical) were conducted. To determine the effect of loading orientations on rupture, the seeds or kernels were positioned horizontally, with the major axis of the seed being normal to the direction of loading. For vertical loading, the major axis of the seed was parallel to the direction of loading (Fig. 2). Force (N) Fig. 1 60 45 30 15 0 0 0.2 0.4 0.6 0.8 1 Deformation (mm) Typical force deformation characteristics. Direction of load Cross head of universal testing machine Direction of load (a) Horizontal orientation (b) Vertical orientation Fixed compression table Fig. 2 Orientations of sunflower seed of sunflower seed under compressive loading.

40 Some Engineering Properties of Sunflower Seed and Its Kernel The experiments for all moisture contents and size categories were carried out with five replications and subsequently the average values were reported. Microsoft Excel software (2003) was employed to compute the statistical parameters including: average, minimum, maximum, standard deviations, correlation coefficients of dimensions and regression equations. 3. Results and Discussion 3.1 Geometrical Properties Dimensions, Geometric mean Diameter and Sphericity The variation of the length, width, thickness, geometric mean diameter and sphericity, of the sunflower seed and its kernel at different moisture content for each size category are shown in Tables 1 and 2. The results showed that all these parameters increase with increasing moisture content from 3% to 14% d.b for all size categories. This indicates that during the moisture absorption process, the sunflower seed and its kernel will simultaneously expand in all dimensions. Deshpande et al. [10] reported similar results for soybean. For the studied range of moisture content (3-14% d.b.), the highest average expansion was along the length and the lowest along the thickness, but for sunflower kernel the highest and lowest average expansion was along the width and along the length, respectively. Deshpande et al. [10] found that the expansion rate of soybean seeds to be the largest along their thickness in comparison with their other two principal axes. The range of length, width and thickness for sunflower seed at studied moisture content was 13.27-15.06, 7.87-9.26 and 3.88-4.94 mm, respectively. These values for sunflower kernels were 10.53-11.57, 4.99-5.73 and 2.32-2.84 mm, respectively. Gupta and Das [14] reported the ranges of 8.92-9.52 and 7.23-8.28 mm for the length of a variety of sunflower seed and kernel, respectively. They also reported the ranges of 3.92-5.12 and 2.52-3.27 mm for width and thickness of sunflower seed, in same way they reported 3.59-4.09 and 2.09-2.43 mm for width and thickness of sunflower kernel. The ranges of geometric mean diameter for sunflower seed and its kernel were 7.4-8.85 and 4.96-5.76 mm, respectively. Gupta and Das [14] reported 4.72 and 3.46 mm for geometric mean diameter of sunflower seed and kernel respectively. Also, the variation of geometric mean diameter for sunflower seed was indicated as 6.15-7.93 mm when moisture content ranged from 10.06-27.06% [31]. As it can be found from Tables 1 and 2, the sphericity for both seed and kernel increased with increase in size. Also, the sphericity of kernel was more dependent to the studied variables than seed. This might be attributed to cellular organization or structure of the kernel. The average sphericity for sunflower seed and kernel was reported 0.57 and 0.53, respectively by Gupta and Das [14]. Isik and Izil [31] indicated an increase in sphericity of sunflower seed (0.79 to 0.84) with increase in moisture content. 3.2 Gravimetrical Properties True Density, Bulk Density and Porosity The experimental results of the true density, bulk density and porosity of sunflower seed and its kernel for the studied size categories at various moisture contents are shown in Tables 3 and 4. According to these Tables, it is apparent that true density and porosity of sunflower seed and its kernel increase when moisture content increase. However, a decreasing trend was observed between bulk density and moisture content. The true density of sunflower seed and its kernel for all sizes varied from 718.59-800.70 and 1109.6-1249.9 kg m -3, respectively. Gupta and Das [14] found the true density of sunflower seed and kernel in the range of 706-765 and 1050-1250 kg m -3, respectively. Isik and Izil (2007) [31] reported the true density of sunflower seed in the range of 885-902 kg m -3 when moisture varied from 10.06% to 27.06%. An increase in true density with moisture content was also reported for cumin seed [25], white lupin [26], guna seeds [32] and pigeon pea [23]. However, Deshpande

Some Engineering Properties of Sunflower Seed and Its Kernel 41 Table 1 Geometrical properties of sunflower seed at different moisture content and size. Length (mm) 14.13 14.24 13.27 14.54 14.53 13.31 15.06 14.73 13.50 Width (mm) 8.94 8.09 7.87 9.15 8.13 7.93 9.26 8.25 8.22 Thickness (mm) 4.78 4.07 3.88 4.81 4.17 4.13 4.94 4.24 4.38 Diameter (mm) 8.45 7.77 7.4 8.62 7.87 7.73 8.85 8.13 7.86 Sphericity 0.6 0.55 0.56 0.59 0.54 0.58 0.59 0.55 0.58 Table 2 Geometrical properties of sunflower kernel at different moisture content and size. Length (mm) 11.30 11.23 10.53 11.45 11.38 10.67 11.57 11.51 10.83 Width (mm) 5.40 4.96 4.99 5.57 5.12 5.08 5.73 5.22 5.21 Thickness (mm) 2.51 2.36 2.32 2.71 2.49 2.46 2.84 2.83 2.62 Diameter (mm) 5.35 5.08 4.96 5.57 5.24 5.12 5.73 5.4 5.29 Sphericity 0.47 0.45 0.47 0.49 0.46 0.5 0.49 0.47 0.49 Table 3 Gravimetrical properties of sunflower seed at different moisture content and size. True density (kg m -3 ) 738.42 718.59 730.59 772.19 735.32 744.57 800.7 763.13 761.16 Bulk density (kg m -3 ) 419.9 449.4 469.5 391.86 427.36 435.58 375.1 414.74 415.56 Porosity (%) 43 37 36 49 42 41 53 46 45 Table 4 Gravimetrical properties of sunflower kernel at different moisture content and size. True density (kg m -3 ) 1190.1 1149.7 1109.6 1219.9 1174.4 1134.5 1249.9 1195.7 1160 Bulk density (kg m -3 ) 578.06 589.4 609.94 559.94 570.1 591.9 539.84 549.4 580.7 Porosity (%) 51 49 45 54 51 48 57 54 50 and Ojha [10], Joshi et al. [11], Suthar and Das [33] found that the true density decreases with increasing moisture content for soybeans, pumpkin seeds and karigda seeds, respectively. The range of bulk density at different moisture levels for seed and kernel were obtained between 375.10-469.50 and 539.84-609.94 kg m -3, respectively. The results showed that the bulk density of seeds was lower than that of kernels for all size categories in the whole range of moisture content under study. This might be attributed to the hull or the seed coat which is bulkier than the kernel such that it causes a considerable reduction in the total mass per unit volume occupied by the seed. The same results were also reported for sunflower seed [33]. They reported the bulk density of seeds and kernels in the range of 438-465 and 570-625 kg m -3, respectively. A similar decreasing trend of bulk density with moisture content

42 Some Engineering Properties of Sunflower Seed and Its Kernel has been reported by for soybean [10], lentil seeds [13], neem [34], white lupin [26] and jatropha seed [29], respectively. It can be implied that such materials become more turgid in the presence of moisture, consequently occurring the dilation phenomenon of bed structure which is very important for silo structural analysis. However, a direct correlation between bulk density and moisture content was found for some other agricultural particulate materials such as for pistachios [35], karingda seeds [33] and coffee [36], respectively. As it can be seen from Tables 3 and 4, the porosity linearly increased with increase of moisture content. Also, the porosity of kernel was higher than that of seed in all size categories and moisture levels. The porosity of seeds and kernels ranged from 36-53 and 45-57%, respectively. In agreement with these results Gupta and Das [14] reported that the porosity of sunflower seeds and kernels increased from 34.3% to 43.3% and 45.5% to 50.2%, respectively when the moisture content changed from 4% to 20% d.b.. Furthermore, Isik and Izil [31] also reported that the porosity of sunflower seed varied from 53.06% to 54.93%. The linearly increasing trend of porosity with increase of moisture content was also observed by other researchers, such as Carman [13], Singh and Goswami [25], Ogut [26], Baryeh and Mangope [23] for lentil seeds, cumin seed, white lupin and pigeon pea, respectively. In contrast, Deshpande et al. [10], Joshi et al. [11], Suther and Das [33], Chandrasekar and Visvanathan [36] reported a linearly decreasing trend of porosity with increase of moisture content for soybean, pumpkin seed, karingda seed and coffee, respectively. Kashaninejad et al. [37] reported a nonlinearly decreasing trend of porosity with moisture content for pistachio. These discrepancies can be related to the cell structure and the variation of densities in different seeds and grains when moisture content is altered. 3.3 Static Coefficient of Friction Table 5 shows the variation of static coefficients of friction for sunflower seed and its kernel on five different surfaces. Static coefficients of friction of seed and kernel on studied surfaces increased as moisture content increased from 3% to 14% for all size categories. This may be explained by increased cohesive force of wet seeds with the structural surface, since the surface becomes stickier as moisture content increases. Similar findings were reported for almond nut [38], pistachio nut and kernel [27], caper fruit [39] and barbunia bean [40]. Also, the results showed that the highest value of static coefficient of friction for both seed and kernel was on the rubber surface, followed by plywood, polyethylene, galvanized iron, and finally aluminium surfaces. In addition, the static coefficients of friction for sunflower seed were lower than that of sunflower kernel at similar moisture content on the same surfaces. The higher coefficients for sunflower kernel might be attributed to its lower sphericity of shape compared with that of sunflower seed. 3.4 Terminal Velocity The values of terminal velocity of sunflower seed and its kernel for all moisture content and size categories are shown in Table 6. It can be seen, the terminal velocity of sunflower seed and its kernel for all size categories increased as the moisture content increased. The terminal velocity of seed was also higher than that of kernel in all sizes. These differences in results can be attributed to the increase in mass of the individual seed or the kernel per unit, when their frontal areas were presented to the air stream to suspend the material. The other reason is probably that the drag force is affected by the moisture content of particle. The table reveals that terminal velocity of sunflower seed and its kernel varied from 5.36 m/s to 6.12 m/s and 5 m/s to 5.68 m/s, respectively with increasing moisture content from 3% to 14%. Gupta and Das [14] reported that terminal velocity of sunflower seed and kernel increased from 5.8 to 7.6 m/s and 3.5 to 5.8 m/s

Some Engineering Properties of Sunflower Seed and Its Kernel 43 Table 5 Static coefficients of friction of sunflower seed and its kernel at different moisture content and size. Seed Aluminium 0.31 0.31 0.31 0.33 0.33 0.32 0.35 0.34 0.33 Plywood 0.45 0.44 0.43 0.48 0.46 0.45 0.51 0.48 0.48 Galvanized iron 0.37 0.36 0.35 0.39 0.38 0.37 0.42 0.42 0.40 Polyethylene 0.39 0.38 0.37 0.43 0.41 0.40 0.48 0.44 0.44 Rubber 0.49 0.47 0.45 0.51 0.50 0.49 0.54 0.53 0.52 Kernel Aluminium 0.37 0.37 0.36 0.4 0.39 0.38 0.42 0.41 0.4 Plywood 0.51 0.5 0.49 0.54 0.51 0.51 0.57 0.54 0.53 Galvanized iron 0.43 0.41 0.4 0.45 0.46 0.42 0.49 0.47 0.44 Polyethylene 0.46 0.44 0.43 0.5 0.47 0.47 0.55 0.50 0.50 Rubber 0.55 0.52 0.5 0.55 0.57 0.54 0.59 0.57 0.57 Table 6 Terminal velocity (m / s) of sunflower seed and its kernel at different moisture content and size. Seed 5.78 5.36 5.24 5.98 5.56 5.48 6.12 5.86 5.62 Kernel 5.24 5.14 5 5.46 5.36 5.14 5.68 5.56 5.24 with increase in moisture content from 6% to 20%. The increasing trend of terminal velocity with increase of moisture content was also observed by other researchers, such as Joshi et al. [10] for pumpkin seeds, Carman [13] for lentil seeds, Singh and Goswami [25] for cumin seeds, Suthar and Das [33] for karingda seeds, Gupta and Das [14] for sunflower seed, Gezer et al. [41] for apricot pit and kernel. 3.5 Mechanical Properties Rupture Force The results of the force required to initiate seed hull or kernel rupture at different moisture content, size and orientation of loading are presented in Figs. 3-4. As it is seen from Fig. 3, the force required to rupture the hull of sunflower seed for each size category of sunflower seed decreased as the moisture content increased from 3 to 14% d.b for both the orientations of loading. This may be due to the fact that at higher moisture content, the seed became softer and required less force [20]. According to Fig. 4, kernel rupture force also decrease with increase in moisture content. The trend of decreasing rupture force at higher kernel moisture contents might be due to a gradual change in the integrity of the cellular matrix [42]. A similar decreasing trend of rupture force with moisture content has been reported by Liu et al. [8]., Joshi [11]., Gupta and Das [42]., Altuntas and Yildiz [43] and Saiedirad et al. [20] for soybean, pumpkin seed, bean seeds, sunflower seed, faba bean grains and cumin seed, respectively. Investigating the results of rupture force for both sunflower seed and its kernel revealed that the average compressive forces required to cause seed hull rupture were significantly higher (47.1-94.72 N) than those required to rupture the kernel (12.8-35.46 N) in both orientations. In agreement with these results, Gupta and Das [42] reported that the compressive forces needed to initiate rupture of sunflower seed hulls

44 Some Engineering Properties of Sunflower Seed and Its Kernel Rupture force, N 120 100 80 60 40 20 0 0 5 10 15 (% d.b) Fig. 3 Effect of moisture content, orientation of loading and size on rupture force of sunflower seed (, large;, medium;, small;, vertical; - - -, horizontal.). 40 35 30 25 20 15 10 5 0 0 5 10 15 (% d.b) Fig. 4 Effect of moisture content, orientation of loading and size on rupture force of sunflower kernel (, large;, medium;, small;, vertical; - - -, horizontal.). Rupture force, N were higher (35.3-65.2 N) than those required to rupture the kernel (8.5-13.4 N). As it can be found from Figs. 3 and 4, despite of a decrease in rupture force with increasing moisture content from 3 to 14% d.b, an increase in rupture force of seed hull and kernel at 7% d.b for both of the orientations of loading and each size category is seen. This agrees with the results of Gupta and Das [42] for sunflower seed. They reported an increase for force required to rupture the hull of seed and kernel at 8% d.b. This might be attributed to cellular organization or structure of sunflower seed and its kernel. At 7% moisture content (7%), also it was easier to detect the bio yield point for both seed and kernel in all studied treatments. The force required to rupture the hull of seed and kernel increased as seed size increased. This could be due to the fact that with increasing size, higher contact area of the seed (or kernel) with the compressing plates results in the expansion of low stress. This is agreement with the Hertz theory for compression test of food materials. Considering the values presented in Fig. 3 and Fig. 4, the seeds required less compressive force to dehull when loaded under the horizontal as compared to the vertical orientation. But for kernels, the trend was the opposite. This agrees with the results of Gupta and Das [42] for sunflower seed. 4. Conclusions (1) All the main dimensions (length, width and thickness) and geometric mean diameter for all size of seeds and kernels increased linearly with the increase of moisture content. This implies that any delay in the processing of the seeds and their kernel leads to dimensions reduction. (2) Due to moisture gain, the maximum and minimum total average expansions were along the seed length and thickness, respectively, these values for the kernels were along the width and the length, respectively. (3) The results revealed that the sphericity for both seed and kernel increased with increase in size. Also, the sphericity of kernel was more dependent to the studied variables than seed. (4) For all size categories, the true density and porosity of sunflower seed and its kernel increased when moisture content increase. However, a decreasing trend was observed between bulk density and moisture content. (5) Static coefficients of friction of seed and kernel on studied surfaces increased as moisture content increased from 3% to 14% for all size categories. Also, the results showed that the highest value of static coefficient of friction for both seed and kernel was on the rubber surface, followed by plywood, polyethylene, galvanized iron, and finally aluminium surfaces. (6) The terminal velocity of sunflower seed and its kernel for all size categories increased as the moisture content increased. The terminal velocity of seed was also higher than that of kernels in all sizes. (7) Rupture force for both sunflower seed and its

Some Engineering Properties of Sunflower Seed and Its Kernel 45 kernel decreased with an increase in moisture content for all size categories in both horizontal and vertical loading orientations. (8) The seeds required less compressive force to dehull when loaded under the horizontal orientation as compared to the vertical orientation. But for kernels, the trend was the opposite. Also, the compressive forces needed to initiate rupture of sunflower seed hulls were higher (47.1-94.72 N) than those required to rupture the kernel (8.5-13.4 N) in both orientations. (9) The force required to rupture the hull of seed and kernel for both seed and kernel increased as seed size increased. Acknowledgment The authors would like to thank Ferdowsi University of Mashhad for providing the laboratory facilities and financial support. References [1] B.D. Shukla, P.K. Srivastava, R.K. Gupta, Oilseed Processing Technology, Central Institute of Agricultural Engineering Publications, Bhopal, India, 1992. [2] L. Tranchino, F. Melle, G. Sodini, Almost complete dehulling of high oil sunflower seed, Journal of American Oil Chemists Society 61 (1984) 1261-1265. [3] N.N. Mohsenin, Physical Properties of Plant and Animal Materials, 2 nd Revised and Updated Edition, Gordon and Breach Science Publishers, New York, 1986. [4] I. Esref, U. Halil, Moisture-dependent physical properties of white speckled red kidney bean grains, Journal of Food Engineering 82 (2007) 209-216. [5] C.J. Bern, L.F. Charity, Air flow resistance characteristics of corn as influenced by bulk density, ASAE 75 (1975) 3504-3510. [6] S. Wu, S. Sokhansanj, A. Opoku, Influence of physical properties and operating conditions on particle segregation on gravity table, Applied Engineering in Agriculture 15 (1999) 495-499. [7] M.H. Ghasemi Varnamkhasti, A. Mobli, S. Jafari, et al., Some engineering properties of paddy (var. Sazandegi), International Journal of Agricultural Research 5 (2007) 763-766. [8] M. Liu, K. Haghighi, R.L. Stroshine, et al., Mechanical properties of soybean cotyledon and failure strength of soybean kernel, Transactions of the American Society of Agricultural Engineers 33 (1990) 559-565. [9] K. Oje and E.C. Ugbor, Some physical properties of oilbean seed, Journal of Agricultural Engineering Research 50 (1991) 305-313. [10] S.D. Deshpande, S. Bal, T.P. Ojha, Physical properties of soybean, Journal of Food Engineering Research 56 (1993) 89-98. [11] D.C. Joshi, S.K. Das, R.K. Mukherjee, Physical properties of pumpkin seeds, Journal of Agricultural Engineering Research 54 (1993) 219-229. [12] P.C. Bargale, J.M. Irudayaraj, B. Marquis, Studies on reological behaviour of canola and wheat, Journal of Agricultural Engineering Research 61 (1995) 267-274. [13] K. Carman, Some physical properties of lentil seeds, Journal of Agricultural Engineering Research 63 (1996) 87-92. [14] R.K. Gupta, S.K. Das, Physical properties of sunflower seeds, Journal of Food Engineering 66 (1997) 1-8. [15] P.M. Nimkar, P.K. Chattopadhyay, Some physical properties of green gram, Journal of Agricultural Engineering Research 80 (2001) 183-189. [16] C. Ozarslan, Physical properties of cotton seed, Biosystems Engineering 83 (2002) 169-174. [17] A.K. Mahapatra, C. Patrick, P. Diau, Effect of moisture content on some physical properties of sorghum (Mahube variety) seeds, Journal of Agricultural Engineering Research 11 (2002) 1-10. [18] M. Konak, K. Carman, C. Aydin, Physical properties of chickpea seeds, Biosystem Engineering 82 (2002) 73-78. [19] E. Baumler, A. Cuniberti, S.M. Nolasco, et al., Moisture dependent physical and compressional properties of safflower seed, Journal of Food Engineering 10 (2005) 10-16. [20] M.H. Saiedirad, A. Tabatabaeefar, A. Borghei, Effect of moisture content, seed size, loading rate and seed orientation on force and energy required for fracturing cumin seed under quasi-static loading, Journal of Food Engineering 86 (2007) 565-572. [21] E. Altuntas, E. Ozgoz, O.F. Taser, Some physical properties of fenugreek (Trigonella foenum-graceum L.) seeds, Journal of Food Engineering 71 (2005) 37-43. [22] M.B. Coskun, I. Yalcin, C. Ozarslan, Physical properties of sweet corn seed (Zea mays saccharata Sturt.), Journal of Food Engineering 74 (2005) 523-528. [23] E.A. Baryeh, B.K. Mangope, Some physical properties of QP-38 variety pigeon pea, Journal of Food Engineering 56 (2002) 59-65. [24] B. Erica, A. Cuniberti, M. Susana, Moisture dependent physical and compression properties of safflower seed, Journal of Food Engineering 2 (2004) 134-140. [25] K.K. Singh, T.K, Goswami, Physical properties of cumin seed, Journal of Agricultural Engineering Research 64 (1996) 93-98.

46 Some Engineering Properties of Sunflower Seed and Its Kernel [26] M.A. Razavi, A. Rafe, T. Mohammadi Moghaddam, A. Mohammad Amini, Physical properties of pistachio nut and its kernel as a function of moisture content and variety, Journal of Food Engineering Research 56 (2007) 89-98. [27] H. Ogut, Physical properties of white lupin, Journal of Agricultural Engineering Research 69 (1998) 273-277. [28] R.C. Pradhan, S.N. Naik, N. Bhatnagar, et al., Some physical properties of Karanja Kernel, Journal of Industrial Crops and Products 28 (2008) 155-161. [29] D.K. Garnayak, R.C. Pradhan, S.N. Naik, et al., Moisture-dependent physical properties of Jatropha seed (Jatropha curcas L.), Journal of Indian Crops Products 27 (2008) 123-129. [30] R.A. Thompson, G.W. Isaac, Porosity determination of grains and seeds with air comparison pycnometer, Transactions of the American Society of Agricultural Engineers 10 (1967) 693-696. [31] E. Isik, N. Izli, Physical properties of sunflower seeds, International Journal of Agricultural Research 8 (2007) 677-686. [32] N.A. Aviara, M.I. Geandzang, M.A. Hague, Physical properties of guna seeds, Journal of Agricultural Engineering Research 73 (1999) 105-111. [33] S.H. Suthar, S.K. Das, Some physical properties of karingda seeds, Journal of Agricultural Engineering Research 65 (1996) 15-22. [34] R. Visvanathan, P.T. Palanisamy, L. Gothandapani, et al., Physical properties of neem nut, Journal of Agricultural Engineering Research 63 (1996) 19-25. [35] R.H. Hsu, J.D. Mannapperuma, R.P. Singh, Physical and thermal properties of pistachios, Journal of Agricultural Engineering Research 49 (1991) 311-321. [36] V. Chandrasekar, R. Visvanathan, Physical and thermal properties of coffee, Journal of Agricultural Engineering Research 73 (1999) 227-234. [37] M. Kashaninejad, A. Mortazavi, A. Safekordi, et al. Some physical properties of pistachio (Pistachio vera L.) nut and its kernel, Journal of Food Engineering 72 (2005) 30-38. [38] C. Aydin, Physical properties of Almond nut and kernel, Journal of Food Engineering 60 (2003) 315-320. [39] A. Sessiz, R. Esgici, S. Kizil, Moisture-dependent physical properties of caper (Capparis ssp.) fruit, Journal of Food Engineering 79 (2007) 1426-1431. [40] M. Cetin, Physical properties of barbunia bean (Phaseolus vulgaris L.cv. Barbunia ) seed, Journal of Food Engineering 80 (2007) 353-358. [41] I. Gezer, H. Haciseferogullari, F. Demir, Some physical properties of Hacihaliloglu apricot pit and its kernel, Journal of Food Engineering 56 (2002) 49-57. [42] R.K. Gupta, S.K. Das, Fracture resistance of sunflower seed and kernel to compressive loading, Journal of Food Engineering 46 (2000) 1-8. [43] E. Altuntas, M. Yildiz, Effect of moisture content on some physical and mechanical properties of faba bean (Vicia faba L.) grains, Journal of Food Engineering 74 (2007) 174-183.