Thin layer drying and effect of temperature on the drying characteristics of bushbuck (Gongronema latifolium) leaves

Determination of the drying properties of agricultural products holds several benefits, such as nutrient preservation, processing and storage. The effect of air temperature on the drying properties and kinetics of bushbuck leaves at 30, 40, 50, 60 and 70 °C temperature was investigated. The drying time declined as the temperature rose, indicating a falling rate drying phenomenon. Drying models such as Henderson and Pabis, Newton, Modified Page, Page, Midilli and others, Logarithmic, and Two-term were applied and fitted to the experimental data's moisture ratio. The non-linear regression fitting method results showed that the Midilli and other models gave the best-fit description for the drying process. The values obtained for the coefficient of determination (R 2 ) were observed to have varied from 0.9948 to 0.9995 for the various drying models evaluated. In contrast, the sum of square error (SSE) and root mean square (RMSE) estimate was observed to vary from 0.0056 to 0.0007 and 0.0310 to 0.0163, respectively. On the estimate for the effective moisture diffusivity ( D e f f ), it was observed that it depends on temperature and extends from 1.33 × 10 − 9 to 4.83 × 10 − 9 m 2 /s. The value of the activation energy was 26.05 kJ/mol. From this study, it can be deduced that the Arrhenius model could predict the temperature effect on the drying process of bushbuck leaves. • This study investigated the drying properties of bushbuck leaves. • Drying occurred in falling rate period with absence of constant rate period. • The Midilli model shows better fits with experimental data among the models tested. • The values of effective diffusivity ranged from 33 × 10 − 9 to 4.83 × 10 − 9 m 2 /s. • The activation energy for the study was 26.05 kJ/mol.