Effect of moisture content on the physical properties of tiger nut (Cyperus esculentus)

Abstract

The effect of moisture content on the physical properties of the black variety of tiger nut was investigated using a completely randomized design, for four moisture content levels initially at 320 and sun dried to 27, 22 and 17% (wb) moisture contents. In these moisture contents, the major (length), intermediate (width), minor (thickness) and geometric diameter decreased with decreasing moisture content from 16.16 to 13.71, 14.51 to 12.46, 11.94 to 10.40 and 13.69 to 11.80 mm, respectively. The values of the width were generally the highest, followed by generic mean diameter and thickness. The roots surface area decreased with decreasing moisture content but the sphericity decreased from C).8öö to 0.847 at 32 to 27% moisture content and increased thereafter from 0.847 to 0.864 at 27 to 17% moisture content. The particle density increased from 1.095 to 1.197 g cm s at 32 to 27% moisture content, decreased to 1.134 g cm¯3 at 22% (wb) and increased thereafter to 1.175 g cm at 17% moisture content. The bulk density decreased non-linearly with decreasing moisture content from 570.64 to 545.81 kg m % the 1000-root mass also decreased with decreasing moisture content from 1341.82 to 1087.54 g. The porosity followed a polynomial function from 47.35 to 52.32% with decreasing moisture content at 32 and 17%, respectively. The angle of repose decreased non-linearly with tuber moisture content from 24.7 0 at 32% moisture content to 23.30 at 27% moisture content and increased sharply thereafter to 24.5 0 at 17% moisture content. The coefficient of friction decreased non-linearly from 0.57 to 0.39 at 32 to 17% moisture content, increased non-linearly from 0.52 to 0.58 and 0.30 to 0.38 at 32 to 22% moisture content for plywood, paper and rubber, respectively