EFFECT OF SOAKING TIME ON SOME ENGINEERING PROPERTIES OF COWPEA (Vigna unguiculata)

Abstract

The study evaluated the effect of soaking time on some selected engineering properties of black-eye pea and brown beans cowpea variety with a view to providing the necessary data that will aid the design and development of some specific process equipment such as size reduction, cleaning, sorting and grading machines as well as storage components and facilities . Mature seeds procured from the market were manually cleaned and soaked in water at room temperature within the range of 27-31⁰C for 2minutes, 4minutes, 6minutes, 8minutes and 10minutes and the selected response parameters observed. The results showed that length, width, thickness, geometric mean diameter, mass, aspect ratio and surface area increased non-linearly from 8.10mm to 12.00mm, 5.28mm to 7.89mm, 5.23m to 6.91mm, 6.20mm to 8.05mm, 0.33g to 0.52g, 0.71 to 0.77, and 132.70mm² and 134.69mm² respectively as soaking time increased for black-eye pea; while for brown beans variety the results showed that length, width, thickness, geometric mean diameter, mass, aspect ratio and surface area increased non-linearly from 8.03mm to 11.60mm, 5.25mm to 7.78mm, 5.18m to 6.69mm, 6.17mm to 7.85mm, 0.34g to 0.58g, 0.66 to 0.74, and 131.65mm² and 134.51mm² respectively as soaking time increased. More so shape and bulk density decreased non-linearly from 0.86 to 0.78 and 0.77g/cm3 to 0.64g/cm3 with increased soaking time for black-eye pea while for brown beans, it decreased non-linearly from 0.80 to 0.73. The static coefficient of friction on three different material surfaces increased non-linearly from 0.3773 to 0.7089 on rubber, from 0.3772 to 0.6630 on stainless steel, and from 0.4177 to 0.6576 on galvanized steel as soaking time increases for both varieties; while angle of repose increased non-linearly also from 22.30⁰ to 38.01⁰ for both varieties when soaked. From the results, it is recommended to use materials of construction indicating value for angle of repose lower than 31.670 in the manufacture of process components requiring easy movement of products along its surface.

Keywords: Black eye pea, Brown beans, Soaking time, Engineering properties.