FUOYE Journal of Engineering and Technology, Volume 2, Issue 1, March 2017 ISSN: 2579-0625 (Online), 2579-0617 (Paper) FUOYEJET © 2017 118 engineering.fuoye.edu.ng/journal Determination of Selected Moisture -Dependent Physical and Frictional Properties of Shelled Egusi Melon ( Citrullus lanatus Thunb.) 1 *Adesola A. Satimehin and 2 Terseer M. Akaayar 1 Department of Agricultural and Bioresources Engineering, Federal University Oye-Ekiti, Nigeria 2 Department of Agricultural and Environmental Engineering, University of Agriculture, Makurdi, Nigeria adesola.satimehin@fuoye.edu.ng|takaayar@gmail.com Abstract— Physical and frictional properties were determined for shelled (i.e. hulled) seeds of egusi melon (Citrullus lanatus Thunb) at moisture content levels of 11.04, 15.7, 21.03 and 24.78 % dry basis. The physical properties investigated were true density, bulk density and the angle of repose; while the frictional properties were the coefficient of static friction and the coefficient of internal friction. Densities were determined using the volume displacement method, while the bulk porosity was calculated as a function of the true and bulk densities. The angle of repose was measured using the cylinder method. The coefficient of static friction of melon seeds on the surfaces of plywood, galvanized iron and glass was determined by sliding a cell filled with the seeds on a tilting table overlaid with the test material surfaces. The coefficient and internal angle of friction were determined by means of a shear test apparatus. Within the range of moisture investigated, the true density of shelled melon seeds decreased from 1,264 to 1,239 kg/m 3 while its bulk density increased from 668 to 681 kg/m 3 . The porosity decreased from 47.19 to 45.36 % while the angle of repose increased from 31.0 to 34.9°. The coefficient of friction of shelled melon seeds on the surfaces of glass, galvanised iron and plywood increased from 0.329 to 0.475, 0.364 to 0.476 and 0.408 to 0.559 respectively. The coefficient and angle of internal friction increased from 0.638 to 0.668 and 32.52 to 33.74°, respectively. These findings are valuable data for efficient design of machines for processing, handling and storage of hulled seeds of egusi melon. Keywords— Moisture content, shelled egusi melon seeds, friction, flow characteristics. ——————————  —————————— 1 INTRODUCTION elon (Citrullus lanatus Thunb.), popularly called "egusi" in many parts of West Africa, is a tendril herbaceous plant, belonging to the family Cucurbitaceae. The seeds of Citrullus lanatus are generally small. When dry (≤ 14.65 % dry basis) they measure about 12 - 13.63 mm long, 8.0 - 8.03 mm wide and 2.02 - 2.30 mm thick (Oloko and Agbetoye, 2006; Bande et al., 2012). The seeds of C. lanatus are flat comprising a thin golden yellow shell (Fig. 1a) and a white cotyledon (Fig. 1b). The cotyledon contains about 30% protein and over 50% oil (Oloyo, 1977). Out of the oil content, 50% is made of unsaturated fatty acids (35% linoleic and 15% oleic) while the remaining 50% oil content is made of saturated fatty acids, which are stearic and palmitic acids. The presence of unsaturated fatty acid makes melon nutritionally desirable. It is also a good source of vitamin B1, vitamin B2 and many minerals including zinc, iron potassium, phosphorus, sulphur, manganese, calcium, lead and magnesium (Eugene and Gloria, 2002; Bande et al., 2012). The oil of Citrullus lanatus seed can be used in the manufacture of margarine, shortening, cosmetics and cooking oils, while the residual cake is a useful source of protein for livestock feed. (a) (b) Fig 1: Pictorial representation of unshelled seeds (a) and cotyledon (b) of egusi melon (Citrullus lanatus Thunb) *Corresponding Author The seed of C. lanatus may be fermented to yield a highly proteinaceous condiment called 'ogiri'. Soups and gravies prepared using 'ogiri' are generally relished much the same way as those that contain condiments made from the locust bean seed (i.e. iru or dawadawa). According to Giwa, Abdullah and Adam (2010) egusi melon seed oil is a potential feedstock for biodiesel production. However, freshly harvested fruits of egusi melons do not store well. Soon after harvest, the seeds begin to germinate and thereby become unfit for human consumption. Besides, and quite unlike watermelon (Citrullus colocynthis Schrad.) the fruits of C. lanatus are not edible in their fresh state because of their bitter, hard, white flesh. Accordingly, they must be processed into more utilizable products such as margarine and the other products earlier mentioned. The postharvest processing and handling of egusi melon involve certain unit operations such as depodding, washing, drying, hulling (also called shelling), seed milling, and oil expression. Most of these operations when performed manually are often boring, strenuous, time-consuming, and tedious. In order to reduce or eliminate the tedium and drudgery associated with manual processing, it is imperative to mechanize the operations, especially as they apply to the processing of the cotyledon (or kernel) of melon seeds. In the design of machines for handling and processing of food and agricultural products, certain engineering properties of the material constitute important and essential engineering data (Karimi et al., 2009). Obi and Offorha (2015) stated that various physical and mechanical properties of seeds depend on moisture content and are important in the design of handling, transportation, storing, drying and processing equipment. Therefore, knowledge of engineering properties of melon seeds, is fundamental because it facilitates the efficient design of M