Mathematical modelling of drying kinetics of oven dried Hibiscus Sabdariffa seed

Abstract

Hibiscus sabdariffa or Roselle seed is an agricultural product which possesses a large amount of nutritional content that could be useful in wide application. Drying process can be helpful to conserve the seeds for long storage periods. For this reason, the drying behavior of Roselle seeds was investigated using laboratory oven at various drying temperatures (35, 45, 55, 60 and 65°C). It is found that the drying process of the Roselle seeds consists of constant rate and mostly falling rate period at where the moisture content of Roselle seed decreases as time goes. Adequately suitable drying temperature is found to be 65°C with the drying time of 240 minutes. The drying behavior of Roselle seeds is further understood through the drying kinetics of the Roselle seeds. Five empirical mathematical models were selected to describe and compare the drying characteristics of Roselle seeds at respective drying temperatures. Drying rate constants, coefficients and statistical parameters were determined by non-linear regression analysis, and therefore, the diffusion approach model was selected as the best model with R value obtained is 0.999 while MBE, RMSE and χ2 values of 2.37E-04, 0.01335 and 0.007794 respectively.