Characterization and Evaluation of Physical and Mechanical Properties of un hulled Arabica Coffee Bean

Abstract

This work was carried out to characterize the physical and mechanical properties of unhulled arabica coffee bean. The results of this work found that at moisture content of 18.76 ± 0.19 % wb, the average length, width, thickness, geometric diameter and surface area of unhulled coffee bean ranged from 12.04 ± 1.06 mm, 8.24 ± 0.45 mm, 4.99± 0.34 mm, 7.90 ± 0.38 mm and 196.44 ± 19.09 mm2 respectively. The average mass and volume ranged from 0.21 ± 0.06 g and 0.21 ± 0.06 cm3 respectively. The average particle density, bulk density and sphericity ranged from 1.00 ± 0.02 g/cm3, 0.40 ± 0.01 g/cm3 and 0.66 ± 0.04% respectively. The average porosity, aspect ratio, and shell content ranged from 60.16 ± 1.09 %, 68.88 ± 6.38% and 16.55 ± 5.70% respectively. The average hardness and fracturability ranged from 12.34 ± 1.28 gf and 2.45 ± 0.08 gf respectively. Regarding the angle of repose on the surface of stainless steel, aluminum, acrylic, and plywood results showed that the average emptying angle of repose ranged from 26.88 ± 3.67°, 29.44 ± 3.35°, 30.01 ± 4.83° and 40.0° ± 7.00° respectively, and the average filling angle of repose ranged from 32.02 ± 2.880°. Concerning friction, results of measurement indicated that average static friction of stainless steel, aluminum, acrylic, and plywood ranged from 0.36 ± 0.02, 0.40 ± 0.03, 0.38 ± 0.04 and 0.45 ±0.03 respectively. The highest emptying angle of repose occurred on the surface of plywood inversely of that was occurring on the surface of stainless steel. There was a positive relationship between the angle of repose and the static friction.