1. Introduction

Pulses play an important role in supply the needs of food in human society, especially in the developing countries. Chickpea (Cicer arientum L.) is considered the 5th valuable legume in terms of worldwide economical standpoint. Chickpea is planted in Southern and Western areas of Asia and Mediterranean [10].

The chickpea is a good source of protein and carbohydrate and its protein quality is better than other legumes such as pigeon pea, black gram and green gram. It also supply some minerals (Ca, Mg, Zn, K, Fe, P) and vitamins like thiamine and niacin [25].

Information on physical and aerodynamic properties of agricultural products is needed in design and adjustment of agricultural machines [8]. The geometric properties such as size and shape are the most important physical properties considered during the separation and cleaning of agricultural grains [18].

In view of this, several studies have been conducted on the physical properties such as size, shape, bulk density, true density, porosity, angle of repose and coefficient of static and dynamic friction of different agricultural crops, such as; quinoa seeds [24], hemp seed [21], lentil seeds [3], safflower seeds [4], popcorn kernels [12], linseed [22], coriander seeds [5], faba bean [2], cucurbit seeds [16], wheat, barley, chickpea and lentil seeds [9], arigo seeds [6], rice seed [11], Parkia speciosa [1].

In a research, several physical properties of chickpea seeds including the average length, width, thickness, geometric mean diameter, unit mass, projected area, angle of repose, terminal velocity and static and dynamic coefficients as functions of moisture content were evaluated [13]. In another research, some moisture dependent physical properties of chickpea seeds of large kabuli, small kabuli and desi varieties were measured [15].

Because of varietal variability in chickpea seeds, knowing the physical properties of different varieties of them is necessary. The objective of this work was to study some physical properties of four varieties of chickpea seeds (Kaka, Pirooz, ILC, Jam) to develop appropriate technologies in design and adjustment of machines used during harvesting, separating, cleaning, handling and storing of them.

2. Materials and Methods

2.1. Sample Preparation

Four common chickpea varieties called Jam, ILC, Pirooz and Kaka, which are grown in Iran, were prepared from Kurdistan Center for Agricultural and Natural Resources Research. The samples were cleaned manually to remove stones, straw, and dirt and then sieved to remove broken and damaged seeds. Initial moisture content (MC) of samples was determined by using oven method at 105°C for 24 h [7]. Initial MC of Jam, ILC, Pirooz and Kaka were 7.45, 7.82, 6.95, 7.33% (w.b.), respectively.

2.2. Dimensions, Size, Surface Area and Sphericity

From each variety, 100 seeds were selected randomly. Length (L), width (W), and thickness (T) of seeds were the morphological features that were measured by micrometer with 0.02 mm accuracy. The geometric mean diameter, arithmetic mean diameter and surface area of seeds were respectively calculated by using the following equation [23]:

(1)

(2)

(3)

Where: D_g = geometric mean diameter of seed (mm).

D_a = arithmetic mean diameter of seed (mm).

S = surface area of seed (mm²).

The used criteria to describe the shape of the seed are the sphericity. Thus, the sphericity (S_p) was computed as [8]:

(4)

2.3. Dimensions, Size, Surface Area and Sphericity

Mass (M) of individual seeds was measured by using a digital scale with 0.0001 gram accuracy. Seed volumes (cm³) and true density (g.cm^-3) were measured by water displacement method. For each chickpea variety 100 seeds were weighed and replaced in water. Mass of water displaced by the seeds was recorded. Finally true densities (g.cm^-3) were calculated by using the following equation:

(5)

where ρ_t is the true density (g.cm^-3), ρ_w is the water density (1.05 g.cm^-3 at laboratory temperature); M and M_w are mass of seeds and water, respectively [20].

Bulk density, ρ_b, is based on the volume occupied by the bulk sample as poured into a container of known volume. In order to measure the bulk density, the chickpea seeds without any compaction were poured into a calibrated container of known volume and weight. The ratio of the mass and volume was expressed as bulk density:

(6)

where: ρ_b is the bulk density (g.cm^-3), M and V are mass of seeds and box volume, respectively [14].

The porosity (ϵ) was calculated from the measured values of bulk density and true density using the following relationship [17]:

(7)

3. Results and Discussion

3.1. Dimensions, Size, Surface Area and Sphericity

The average, minimum, maximum, standard deviation and coefficient of variation values for the length, width, thickness, geometric mean diameter, arithmetic mean diameter, surface area and sphericity of four chickpea varieties are shown in Tables 1 to 7.

Analysis of the statistical parameters for each variety shows that the Jam and Kaka variety respectively presented high and low mean values for all of mentioned physical properties in table 1 to 7 except sphericity, whose the high mean value belongs to ILC. The mean sphericity of kaka and jam, and mean sphericty of ILC and Jam varieties were in the same range, respectively.

The importance of dimensions is in determining the aperture size of machines, particularly in separation of materials [19]. These dimensions may be useful in estimating the size of machine components. The major axis has been found to be useful by indicating the natural rest position of the material and hence in the application of compressive forces to induce mechanical rupture. The values sphericity indicate strong tendency of seed shape towards a sphere.

Table 1. The statistical parameters for length (mm) of chickpea varieties variety mean min max STD CV kaka 7.5 6.52 9.06 0.453259 6.043456 pirooz 8.45 7.2 9.54 0.49639 5.874438 ILC 9.02 7.76 10.36 0.467218 5.179797 jam 9.69 8.56 10.88 0.512182 5.285679

Table 2. The statistical parameters for width (mm) of chickpea varieties variety mean min max STD CV kaka 5.06 3.56 6.74 0.429583 8.48979 pirooz 5.7 4.62 6.38 0.364721 6.398609 ILC 7.1 5.86 8.82 0.448843 6.321734 jam 7.56 6.14 9.48 0.480685 6.358261

Table 3. The statistical parameters for thickness (mm) of chickpea varieties variety mean min max STD CV kaka 5.16 4.1 5.84 0.334463 6.481847 pirooz 5.85 4.6 6.54 0.323377 5.527809 ILC 7.3 6.48 8.62 0.363139 4.974503 jam 7.74 4.72 10.08 0.548466 7.086125

Table 4. The statistical parameters for geometric mean diameter (mm3) of chickpea varieties variety mean min max STD CV kaka 5.8 5.06 6.61 0.312252 5.383647 pirooz 6.55 5.6 7.33 0.322421 4.922462 ILC 7.76 6.7 8.57 0.34761 4.479515 jam 8.27 7.04 9.86 0.396802 4.798084

Table 5. The statistical parameters for arithmetic mean diameter (mm3) of chickpea varieties variety mean min max STD CV kaka 5.91 5.2 6.73 0.313371 5.302387 pirooz 6.67 5.76 7.45 0.325617 4.881812 ILC 7.81 6.74 8.62 0.348967 4.468209 jam 8.33 7.34 9.86 0.388713 4.666421

Table 6. The statistical parameters for surface area (mm2) of chickpea varieties variety mean min max STD CV kaka 105.93 80.32 137.17 11.4222 10.78278 pirooz 136.1 98.65 219.64 13.09677 9.6229 ILC 189.7 140.86 230.54 16.82481 8.869169 jam 215.49 155.85 305.59 20.8167 9.66017

Table 7. The statistical parameters for sphericity (%) of chickpea varieties variety mean min max STD CV kaka 77.37 69.3 85.07 2.669184 3.449896 pirooz 77.62 67.68 83.5 2.752797 3.546505 ILC 86.15 80.61 93.81 2.6545 3.081254 jam 85.46 73.83 98.23 3.537803 4.139718

3.2. Mass, True Density, Bulk Density and Porosity

The average, minimum, maximum, standard deviation and coefficient of variation values of Mass are shown in table 8. As this table shows the Jam and Kaka variety respectively presented high and low mean values of seeds mass.

Table 9 shows the average values of true density, bulk density and porosity for chickpea seeds. It appears that true and bulk density decrease, and porosity increases with regard to increasing size.

The seed mass, bulk density and true density are very important in separating and grading of grains according to density and aerodynamic properties.

Table 8. The statistical parameters for mass (g) of chickpea varieties Variety mean min max STD CV kaka 0.129 0.088 0.194 20.91658 16214.41 pirooz 0.202 0.133 0.31 31.03208 15362.42 ILC 0.324 0.215 0.454 45.08071 13913.8 jam 0.391 0.292 0.49 46.35728 11856.08

Table 9. The average values of true density, bulk density and porosity for chickpea seeds variety True density(g.cm-3) Bulk density(g.cm-3) Porosity(%) kaka 1.408 0.825 41.4 pirooz 1.402 0.809 42.3 ILC 1.386 0.772 44.3 jam 1.379 0.759 45

4. Conclusions

The present study provides information on some physical properties of four Iranian varieties of chickpea. The results showed that these properties vary from variety to variety. Among the varieties, jam had the highest and kaka had the lowest values of geometric properties. The maximum values of bulk density and true density among the varieties were obtained for kaka, and jam had the highest porosity.

This data can be used for design and adjustment of agricultural machines in agricultural process of these varieties of chickpea. Another application of this data can be recognition and classification of them.