Effects of moisture content on some physical properties of lentil seeds M.N. Amin * , M.A. Hossain, K.C. Roy FMP Engineering Division, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur 1701, Bangladesh Received 5 July 2003; accepted 15 December 2003 Abstract This study was carried out to determine the effect of moisture content on some physical properties of lentil seeds. Four levels of moisture content ranging from 10.33% to 21.00% (wet basis) were considered in this study. The shape of the lentil seed was a disc shape with dimensions of diameter and thickness. Diameter, thickness, porosity, mass of 1000 seeds and angle of repose increased linearly from 3.84 to 4.06 mm, 2.18 to 2.48 mm, 34.48 to 37.00%, 20 to 25.5 g and 24.80 to 27.78°, respectively with increase in moisture content from 10.33% to 21.00%. Bulk density and kernel density decreased linearly from 832 to 768 kg/m 3 and 1270 to 1212 kg/m 3 , respectively with increase in moisture content from 10.33% to 21.00%. Static and kinetic coefficients of friction of lentil seeds were determined on a smooth concrete, galvanized iron, plywood and glass sheets at various moisture contents. They varied from material to material and depended on the roughness and wetness of the seeds. The highest static and kinetic coefficients of friction were found on the concrete surface and the lowest on the glass sheet among the materials tested. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Coefficient of friction; Lentil; Moisture content; Physical properties 1. Introduction Lentil (Lens culinaris Medik) is an important pulse crop in Bangladesh. It has good digestibility, flavour and high protein content. It has the ability to overcome malnutrition problems of the poor due to being rich in protein (23–24%) (Rajput & Sarwar, 1988). In Bangla- desh, each year about 128 000 tons of lentil are produced from 412 000 ha of land (Anon, 2000). Lentil has a po- tential export market in India, Pakistan, countries of the Middle East and some extent in European countries. Recently scientists have made great efforts in evalu- ating basic physical properties of agricultural materials and have pointed out their practical utility in machine and structural design and in control engineering (Waziri & Mittal, 1983). Recent scientific developments have improved the handling and processing of bio-materials through mechanical, thermal, electrical, optical and other techniques, but little is known about the basic physical characteristics of bio-materials. Such basic information is important not only to engineers but also to food scientists, processors, plant breeders and other scientists who may find new uses (Mohesenin, 1980). Dimensions are important to design the cleaning, sizing and grading machines. Bulk density, kernel density and porosity are major considerations in designing the dry- ing and aeration and storage systems, as these properties affect the resistance to air flow of the mass. Angle of repose and coefficient of friction are important in designing equipment for solid flow and storage struc- tures. The coefficient of friction between seed and wall is an important parameter in the prediction of seed pres- sure on walls (Gumble & Maina, 1990). Several investigators determined the physical proper- ties of pulse and oilseed seeds at various moisture con- tents such as Dutta, Nema, and Bhardwaj (1988) and Chowdhury, Sarker, Bala, and Hossain (2001) for gram; Shepherd and Bhardwaj (1986) for pegionpea; Sreen- arayana, Visvanathan, and Subramanijam (1988) and Hossain, Alam, and Huq (1995) for sunflower seeds; Kaleemullah (1992) and Hossain, Khaleque, and Has- san (1998) for groundnut kernel and Kanawde, Bhosale, and Kadam (1990) for pegeonpea, pea, green gram, blackgram, soybean and mothbean. Carman (1996) determined physical properties such as diameter, thick- ness, unit mass, volume, bulk density and porosity of Turkish lentils in the moisture range of 6.5–32.6% (db). He also presented the static and dynamic coefficients of friction of lentil seed against galvanized sheet, plywood and rubber surfaces. Although Bangladesh does not Journal of Food Engineering 65 (2004) 83–87 www.elsevier.com/locate/jfoodeng * Corresponding author. E-mail address: barifmpe@bttb.net.bd (M.N. Amin). 0260-8774/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2003.12.006