Moisture-dependent physical properties of white speckled red kidney bean grains Es ßref IS ß IK * , Halil U ¨ NAL Department of Agricultural Machinery, Faculty of Agriculture, Uludag University, Bursa 16059, Turkey Received 24 April 2006; received in revised form 31 January 2007; accepted 1 February 2007 Available online 20 February 2007 Abstract Physical and mechanical properties of food crops gain importance during harvesting with machines, separation and cleaning processes of this crop and also during the designation or improvement of this type of machines. Therefore, this study was conducted to investigate some moisture-dependent physical properties of round red lentil 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 and shelling resistance. In the study, the average length, width and thickness were 9.222, 12.843 and 7.062 mm, at a moisture content of 9.77% d.b., respec- tively. The arithmetic and geometric mean diameters increased 7.92% and 8.95%, respectively, while the sphericity decreased 3.40% with an increase in the moisture content range 9.77–19.62%. In the moisture range from 9.77% to 19.62% d.b., studies on rewetted white speckled red kidney bean grains showed that the thousand grain mass increased 7.32%, the projected area from 55.17% mm 2 , the true density 12.91%, the porosity from 46.40% to 58.22% and the terminal velocity from 10.40%. The bulk density decreased 13.57% with an increase in the moisture content range of 9.77–19.62% d.b. The static coefficient of friction of white speckled red kidney bean grains increased the linearly against surfaces of six structural materials, namely, rubber (16.48%), aluminum (22.42%), stainless steel (24.45%), galvanized iron (17.64%), glass (25.82%) and MDF (23.71%) as the moisture content increased from 9.77% to 9.62% d.b. The shelling resistance of white speckled red kidney bean grains decreased as the moisture content increased from 98.26 to 53.67 N. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: White speckled red kidney beans; Physical properties; Moisture content 1. Introduction A white speckled red kidney bean (Turkish name’s Barbunia) (Phaseolus vulgaris L.cv. ‘Barbunia’) is a culti- vated plant grown for fresh and dry consumption and raw material of canned food industry. It contains 23.1 g protein, 1.7 g oil, 59.4 g carbohydrates, 163 mg calcium, 6.9 mg iron, 437 mg phosphor and 336 cal energy per 100 g (dry) (Anonymous, 2006a). Turkey has about 155,000 ha of dry bean harvesting area, 250,000 tons of dry bean production per annual with a yield of 1616 kg ha 1 of bean (FAOSTAT, 2004). In addition to this Turkey had about 18,000 ha of white speckled red kidney bean harvesting area and 43,000 tons of white speckled red kidney bean production per annual in 2002 (Cetin, 2007). The knowledge of physical properties constitutes impor- tant and essential engineering data in the design of machines, storage structures, and processes. The value of this basic information is not only important to engineers but also to food scientists, processors, and other scientists who may exploit these properties and find new uses. The size and shape are, for instance, important in their electrostatic 0260-8774/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2007.02.012 * Corresponding author. Fax: +90 0 224 442 91 49. E-mail addresses: dresref@uludag.edu.tr (E. IS ßIK), dresref@gmail.com (H. U ¨ NAL). www.elsevier.com/locate/jfoodeng Journal of Food Engineering 82 (2007) 209–216