Watermelon seeds of three major local Iranian varietiesSarakhsi, Kolaleh and Red, at the moisture content of 4.55, 4.75 & 5.02% (w.b.), were selected to study the physical properties, respectively. Linear dimensions, mean diameters, sphericity, surface area, volume, true and bulk densities, porosity, repose angles and static coefficient of friction of the three varieties’ seeds were measured using standard methods. The results showed that the length, width, thickness, arithmetic mean diameter and geometric mean diameter of watermelon seeds varied from 13.45 to 18.97 mm, 8.4 to 10.7 mm, 2.91 to 3.10 mm, 8.256 to 10.894 mm and 6.893 to 8.456 mm, respectively. While The sphericity by Jean & Ball’s method, sphericity by the Mohsenin’s method, surface area by McCabe et al’s method and surface area by Jean & Ball’s method, changed from 2.004 to 2.125, 0.446 to 0.513, 149.68 to 225.03 mm2, 128.09 to 198.01 mm2, respectively. The values of the seed volume, true density, bulk density and porosity of watermelon seeds were between 179.53-311.62 mm3, 861.75-866.66 kg/m3, 416.33-527.265 kg/m3 and 39.14-51.68% respectively. The study over the coefficient of friction of watermelon seeds on some materials such as plywood, galvanized metal sheet, glass, fiberglass and rubber showed that the static coefficient of friction varied from 0.26 on glass to 0.676 against rubber. Furthermore, the filling and funneling angles of repose for three watermelon seeds ranged from 27.092 to 32.38, 21.662 to 28.146, respectively. It is concluded that the physical properties of watermelon seeds vary from variety to variety and it is also a function of the seed moisture content, environmental and growth conditions.
Key words: Watermelon seeds; Gravimetrical properties; Geometrical properties; Frictional properties
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