Storage stability of selected agricultural grains

Abstract

Three grains maize, sorghum and millet were stored at different levels of moisture contents 10%, 20%, 30%, 40%, 50 %, 60 %, 70 %, 80%, 90 % and 98 % wet basis in order to determine the optimum moisture content for maximum grain stability. The effects of moisture content levels on their quality at three different temperatures levels (20 °C, 25°C and 40°C) were cvaluated. The Rockland (1969) concept of local isotherm was used to interpret the responses of the physical properties while the free energy equation was used to evaluate the energy levels of the grains at these moisture contents. This resulted in stability curves which showed that grains equilibrated by desorption (drying) have a two point minima levels (11.40 and 18.81 % at 20 °C, 12.75 and 18.84 % at 25 °C and 15.00 and 18.48 % at 40 °C for maize; 11.46 and 18.92 % at 20 °C, 11.36 and 18.92 % at 25 °C and 12.29 and 18.62 % at 40 °C for sorghum; 13.45 and 19.81 % at 20 °C, 14.79 and 21.20 % at 25 °C and 14.25 and 20.85 % at 40 °C for millet) that gives rise to a wider safe moisture range than by adsorption (humidification). The results further revealed that the three grains showed optimum moisture for stability above which deterioration takes place rapidly.