Applied Engineering in Agriculture Vol. 22(2): E 2006 American Society of Agricultural and Biological Engineers ISSN 0883-8542 DETERMINATION OF SELECTED PHYSICAL PROPERTIES AND THEIR RELATIONSHIPS WITH MOISTURE CONTENT FOR MILLET (PENNISETUM GLAUCUM L.) V. I. O. Ndirika, O. O. Oyeleke ABSTRACT. Selected physical properties of millet crop (Pennisetum glaucum L.) such as kernel volume, length, width, thickness, geometric mean diameter, surface area, sphericity, roundness, angle of repose, thousand kernel weight (TKW), specific gravity, bulk density, and porosity were determined as a function of moisture content. Kernel volume and other dimensions such as length, width, thickness, and geometric mean diameter vary linearly and are directly proportional with the grain moisture content (ranging between 7.5% and 21.2% wet basis). A comparative evaluation of two varieties of millet (Ex-Borno and Zango) for the above properties revealed that only the difference in the means of surface area, specific gravity, and grain density were not statistically significant at the 5% level of significance, while the difference with the other properties such as length, width, thickness, geometric mean diameter, volume, sphericity, roundness, angle of repose, thousand kernel weight, bulk density, and porosity were statistically significant at the 5% level. Correlation coefficients between 76% and 95% were obtained with the relationship between moisture content and grain length, width, geometric mean diameter, and grain volume for both varieties of millet. Keywords. Physical properties, Moisture content, Millet. illet (Pennisetum glaucum L.) which is one of the most important cereal crops in the tropics can be processed into flour and used for making pap and porridge. It belongs to the graminea (poaceae .I) family, producing small edible seeds used as for- age crops and as food cereals. In Sub-Sahara, millet grains are used for human consumptions while the remain are used as fodder, although some farmers would feed their working (draught) animals as supplements during the working season. The varieties mainly grown in the savannah zone of Nigeria are Zango, Ex-Borno, Maiwa, and Gaura. The Ex-Borno va- riety constitutes 90% of all millet grown (Ndirika, 1994) and grows at an annual production rate of 2.1% (Abalu, 1978). Some varieties of millet such as Zango and Ex-Borno are being used for the production of biscuits, confectionaries, beverages, pharmaceutical syrups, and brewing beer. In developed countries, particularly the United States, millet is grown mainly as feed for livestock and poultry production as well as for production of starches, crystalline sugar, and paper adhesives (Dogett, 1970; Jackson et al., 1981). Determination of the physical properties of agricultural materials is often problematic because of their diversity of Article was submitted for review in February 2005; approved for publication by the Food & Process Engineering Institute Division of ASABE in December 2005. The authors are Victor I. O. Ndirika, Senior Research Fellow/Senior Lecturer, and Oyelola Oyeleke, Department of Agricultural Engineering, Institute for Agricultural Research, Ahmadu Bello University, Zaria, Nigeria. Corresponding author: Victor I. O. Ndirika, Department of Agricultural Engineering, Institute for Agricultural Research, Ahmadu Bello University, Zaria, Nigeria. Phone: 2348035929353; fax: 234069-550563; email: vndirika@yahoo.com. shape, size, moisture content, and maturity level. Recent scientific developments have improved the handling and processing of biomaterials through mechanical and thermal devices, but little is known about the basic physical characteristics of these materials (Waziri and Mittal, 1983). Such basic information is not only important to engineers but also to food scientists and processors, plant and animal breeders, and other scientists involved in handling and processing (such as transportation, drying, threshing, clean- ing, aeration grading) and design of post-harvest machines. Oyeleke (2002) and Mohammed (2002) reported that grain length, width, thickness, and volume increases as moisture content increases for millet and wheat grain; sorghum and maize grains, respectively. A review of literature revealed limited works have been performed on the physical properties of millet (Waziri and Mittal, 1983). However, post-harvest machines designed with their data can, to some extent, not function effectively because of the peculiarity of some of the grains obtained and also the differences in agroclimatic zones, which can cause the grains to be smaller or larger in size. Recent studies on cereal threshing using a mechanical thresher indicate that moisture content is an important parameter influencing threshing effectiveness and mechani- cal damage of crop (Ndirika, 1997). The importance of moisture content in relation to handling, processing, and design of post-harvest machines is justified. OBJECTIVE The objectives of this study were: (1) to compare selected physical properties of Zango to Ex-Borno varieties of millet, and (2) to determine the relationship between moisture content and the physical properties. M