Soybeans are a cultivated plant grown for dry consumption and raw material of canned food industry. It contains 17 g protein, 1 g oil, 44 g total carbohydrates, 88 mg calcium, 4 mg iron, 1 mg sodium, 6% Calories from fat per 250 mL (dry) (Anonymous, 2006).
Turkey had about 14 000 ha of soybeans harvesting area, 50,000 t of soybeans production per annum with a yield of 3571 kg ha-1 of soybeans in 2004 (SIS, 2006).
Some engineering properties have been studied for various beans such as soybean (Deshpande et al., 1993), locust bean seed (Olajide and Ade-Omowage, 1999; Ogunjimi et al., 2002), Sakiz faba bean (Haciseferogullari et al., 2003), barbunia bean (Çetin, 2006), cocoa beans (Bart-Plange and Boryeh, 2003), Turkish gOynük bombay bean (Tekin et al., 2006) and faba bean (Altunta and Yildiz, 2007).
Despite an extensive search, limited work seems to have been carried out on the some engineering properties of soybean and their relationship with moisture content. Hence, this study was conducted to investigate some moisture dependent some engineering properties of soybean grains namely, grain dimensions, thousand grain mass, surface area, projected area, sphericity, bulk density, true density, porosity, terminal velocity, static coefficient of friction against different materials.
MATERIALS AND METHODS
The soybean grains used in the study were obtained from a local market (Marmara Region, Bursa, Turkey). The initial moisture content of the grains was determined by digital moisture meter (Pfeuffer HE 50, Germany) reading to 0.01%.
The samples of the desired moisture contents were prepared by adding the amount
of distilled water as calculated from the following relation (Coskun et al.,
The samples were then poured into separate polyethylene bags and the bags sealed
tightly. The samples were kept at 5°C in a refrigerator for a week to enable
the moisture to distribute uniformly throughout the sample. Before starting
a test, the required quantity of the grain was taken out of the refrigerator
and allowed to equilibrate to the room temperature for about 2 h (Singh and
The soybeans are harvested at about between 9 and 20% w.b.(wet basis) harvesting moisture and dried to the desired moisture contents of 13% w.b. for safe module storage (Isik and Alibas, 2000). Therefore, all the engineering properties of the grains were determined at five moisture contents in the range of 10.62-27.06% d.b. with 10 replications at each moisture content.
To determine the average size of the grain, 100 grains were randomly picked and their three linear dimensions namely, length (L), width (W) and thickness (T) were measured using a digital compass (Minolta, Japan) with a accuracy of 0.01 mm.
The average diameter of grain was calculated by using the arithmetic mean and
geometric mean of the three axial dimensions. The arithmetic mean diameter Da
and geometric mean diameter Dg of the grain were calculated by using
the following relationships (Mohsenin, 1970).
The sphericity of grainsφ was calculated by using the following relationship
The one thousand grain mass was determined by means of an electronic balance
reading to 0.001 g.
The surface area As in mm2 of soybean grains was found
by analogy with a sphere of same geometric mean diameter, using the following
relationship (Olajide and Ade-Omewaye, 1999).
The projected area Ap was determined from the pictures of soybean
grains which were taken by a digital camera (Creative DV CAM 316; 6.6 Mpixels),
in comparison with the reference area to the sample area by using the Global
Lab Image 2-Streamline (trial version) program (Isik and Güler, 2003).
The average bulk density of the soybean grains was determined using the standard test weight procedure reported by Singh and Goswami (1996) and Gupta and Das (1997) by filling a container of 500 mL with the grain from a height of 150 mm at a constant rate and then weighing the content.
The average true density was determined using the toluene displacement method.
The volume of toluene (C7H8) displaced was found by immersing
a weighed quantity of soybean grains in the toluene (Ogüt, 1998). The porosity
was calculated from the following relationship (Mohsenin, 1970):
where Pf is the porosity in %;ρb is the bulk density
in kg m-3 andρt is the true density in kg m-3.
The terminal velocities of grain at different moisture contents were measured using a cylindrical air column in which the material was suspended in the air stream (Nimkar and Chattopadhyay, 2001). The air velocity which kept the grain suspension was recorded by a digital anemometer (Thies clima, Germany) having a least count of 0.1 m sec-1.
The static coefficient of friction of soybean grains against six different
structural materials, namely rubber, galvanized iron, aluminum, stainless steel,
glass and MDF was determined. A polyvinylchloride cylindrical pipe of 50 mm
diameter and 100 mm height was placed on an adjustable tilting plate, faced
with the test surface and filled with the grain sample. The cylinder was raised
slightly so as not to touch the surface. The structural surface with the cylinder
resting on it was raised gradually with a screw device until the cylinder just
started to slide down and the angle of tilt was read from a graduated scale
(Singh and Goswami, 1996). The coefficient of friction was calculated from the
Shelling resistance Rs was determined by forces applied to one axial
dimension (thickness). The shelling resistance of grain was determined under
the point load by using a penetrometer (Bosch BS45 tester, Germany).
RESULTS AND DISCUSSION
As it can be seen in Fig. 1, the three axial dimensions
increased with increase in moisture content from 10.62-27.06% d.b. The mean
dimensions of 100 grains measured at a moisture content of 10.62% d.b. are:
length 7.795±0.0549 mm, width 7.123±0.0246 mm and thickness 4.189±0.0673
The average diameters increased with the increase in moisture content as axial
dimensions. The arithmetic and geometric mean diameter ranged from 6.369 to
8.048 and 6.149 to 7.933 mm as the moisture content increased from 10.62-27.06%
d.b., respectively (Fig. 2).
One Thousand Grain Mass
The one thousand soybean grain mass increased linearly from 200 to 255 g
as the moisture content increased from 10.62-27.06% d.b. (Fig.
3). An increase of 27.5% in the one thousand grain mass was recorded within
the above moisture range.
A linear increase in the one thousand soybean grains mass as the grain moisture content increases has been noted by Saçilik et al. (2003) for hemp, Deshpande et al. (1993) for soybean, Dursun and Dursun (2005) for caper seed and Nimkar and Chatopadhyay (2001) for green gram.
Surface Area of Grain
The Fig. 4 indicates that the surface area increases with
increase in grain moisture content. The surface area of soybean grains increased
polynomial from 118.756 to 197.654 mm2 when the moisture content
increased from 10.62-27.06% d.b.
Different increasing trends have been reported by Dursun and Dursun (2005) for caper seed, Deshpande et al. (1993) for soybean.
Projected Area of Grain
The projected area of soybean grains linear increased from 37.69 to 53.39
mm2, when the moisture content of grain increased from 10.62-27.06%
d.b. (Fig. 5).
Similar trends have been reported by Tang and Sokhansanj (1993) for lentil,
Ozarslan (2002) for cotton and Konak et al. (2002) for chick pea grain
and for Turkish mahaleb.
The sphericity of soybean grains increased polynomialy from 0.789 to 0.835
with the increase in moisture content (Fig. 6). However, linear
trends have been reported by Nimkar and Chattopadhyay (2001) for green gram,
Aydin et al. (2002) for Turkish Mahaleb, Baryeh and Mangope (2002) for
pigeon pea, Sahoo and Srivastava (2002) for okra grain.
The values of the bulk density for different moisture levels varied from
650 to 550 kg m-3 (Fig. 7). Despite the bulk density
soybean grains decreasing polynomialy, a linear decreasing trend in bulk density
has been reported by Gupta and Das (1997) for sunflower grain, Nimkar and Chattapadhyay
(2001) for green gram, Sahoo and Srivastava (2002) for okra, Konak et al.
(2002) for chick pea, Saçilik et al. (2003) for hemp seed and
Coskun et al. (2006) for sweet corn seed.
The true density of soybean grains polynomial increased from 1090 to 1200
kg m-3, when the moisture level increased from 10.62-27.06% d.b.
(Fig. 8). However, linear trends have been reported by Aviara
et al. (2005) for Balanites aegypticiaca nuts and Coskun et
al. (2006) for sweet corn seed.
The porosity of soybean grains increased from 40.36 to 54.16% with the increase
in moisture content from 10.62-27.06% d.b. (Fig. 9). Gupta
and Das (1997), Konak et al. (2002), Nimkar et al. (2005) and
Çalisir et al. (2005) reported increased trends in the case of
sunflower grain, chick pea, moth gram and okra seed, respectively.
The terminal velocity was found to increase polynominaly from 8.01 to 9.1
m sec-1 as the moisture content increased from 10.62-27.06% d.b.
(Fig. 10). Different increasing trend were reported by Joshi
et al. (1993) and Suthar and Das (1996), in the case of pumpkin grains
and karingda, respectively.
Static Coefficient of Friction
The static coefficient of friction of soybean grains on six surfaces (rubber,
stainless steel, aluminum, glass, MDF and galvanized iron) against moisture
content in the range 10.62-27.06% d.b. are presented in Fig.
11. It was observed that the static coefficient of friction increased with
increase in moisture content for all the surfaces. This is due to the increased
adhesion between the grain and the material surfaces at higher moisture values.
Increases of 13.82, 18.51, 8.65, 20.09, 26.01 and 17.55% were recorded in the
case of rubber, stainless steel, aluminum, glass, MDF and galvanized iron, respectively,
as the moisture content increased from 10.62-27.06% d.b. At all moisture contents,
the least static coefficient of friction were on MDF.
The logarithmic relationships between static coefficients of friction and moisture
content on rubber (μrub), stainless steel (μss),
aluminum (μal), glass (μgl),
MDF (μmdf) and galvanized iron (μgi)
can be represented by the following equations:
μru = 0.2166+0.054 Ln
(Mc)(R2 = 0.9786)
μss = 0.1468+0.0607 Ln
(Mc)(R2 = 0.9679)
μal = 0.252+0.0267 Ln
(Mc)(R2 = 0.99726)
μgl = 0.105+0.052 Ln (Mc)(R2
μmdf = 0.0782+0.056 Ln
(Mc)(R2 = 0.9878)
μgi = 0.1598+0.0589 Ln
(Mc)(R2 = 0.9471)
||Effect of moisture content on static coefficient of friction
of soybean against various surface: (□) rubber; (x) galvanized iron;
(Δ) aluminium; (◊) stainless steel; (o) glass; ()
The shelling resistance of soybean was found to decrease with the increase
in moisture content (Fig. 12). The small shelling resistance
at higher moisture content might have resulted from the fact that the grain
became more sensitive to cracking at high moisture. The variation in shelling
resistance of soybean Rs in N with moisture content can be represented
by the following Eq.:
with value for R2 of 0.9744.
The average length, width and thickness of grains ranged from 7.80 to 9.5, 7.12 to 8.34 and 4.189 to 6.3 mm as the moisture content increased from 10.62-27.06% d.b., respectively.
The arithmetic and geometric mean diameters were found to increase from 6.369 to 8.048 mm and 6.149 to 7.933 mm, respectively. The thousand grain mass increased from 472.5 to 696.2 g and the sphericity increased from 0.536 to 0.619 with the increase in moisture content from 10.62-27.06% d.b. The bulk density decreased from 650 to 550 kg m-3, whereas the true density increased from 1090 to 1200 kg m-3. The terminal velocity increased linearly from 8.01 to 9.1 m sec-1 as the moisture content increased from 10.62-27.06% d.b. The static coefficient of friction increased for all four surfaces, namely, rubber (0.3443-0.3919), stainless steel (0.2905-0.3443), aluminum (0.2867-0.3115), glass (0.2309-0.2773), MDF (0.2126-0.2679) and galvanized iron (0.2962-0.3482).
This study was supported by the Research Fund of The University of Uludag and DPT Project number: Z-004/49 and Z-2005/3.
||Surface area (mm2)
||Arithmetic mean diameter of grain (mm)
||Geometric mean diameter of grain (mm)
||Length of grain (mm)
||Initial moisture content of sample (%d.b.)
||Final moisture content of sample (%d.b.)
||Moisture content (%d.b.)
||Shelling resistance (N)
||Coefficient of determination
||Mass of water to added (kg)
||Thickness of grain (mm)
||Width of grain (mm)
||Initial mass of sample (kg)
||Angle of tilt, degree
||Static coefficient of friction
||Sphericity of grain
||Medium density fibreboard