Effect of period of harvest on drying characteristics of an improved variety cowpea (IT 97K-56S-IS)

Abstract

Shattering loss and loss due to pest attack significantly reduce the quantity and quality of cowpea that can be harvested from the field, hence, the possibility of early harvest of cowpea was investigated. Thin-layer drying kinetics of IT 97K-56S-IS was experimentally investigated in a convective dryer and mathematical modelling was performed by using five thin layer drying models. Experiments were performed on samples harvested 60, 64, 68 and 72 Days After Planting (DAP) and drying temperature of 55, 65, 75 and 85ºC. The effect of period of harvest and drying temperature on the drying characteristics and nutritional content of the dried products were determined. The models performance was evaluated by comparing the coefficient of determination (R²) and root mean square error (RMSE) relating the experimental and predicted moisture ratios through non-linear regression analysis. The values of the R² and RMSE vary from 0.967 - 1.000 and 0.001 - 0.061 respectively. Drying process was discovered to have taken place during falling rate period; Page and Logarithmic model gave the best fit with the highest R² value of 0.998 and 1.000 and lowest RMSE values of 0.015 and 0.001 respectively. Proximate analysis result of IT 97K-56S-IS indicates that, carbohydrate content and crude protein ranges between 61.91 - 64.40%; 20.74 - 21.17% respectively.