Mathematical Modeling of Thin Layer Drying of Onion Slices

Onions play significant role in preparing meals and are known to have great medicinal values. An important operation normally deployed in preserving this important vegetable is drying. Dried onions can come in a variety of state which includes flaked, powdered, minced or even chopped. Sun drying with its attendant problems sees the need for  dryers designed and constructed based on models. Drying using an electric oven was tested on onion (Allium cepa) in this study. The drying experiments were performed at different temperature of 50^°C, 60^°C and 70^°C. Drying characteristics of onion was studied and a model that describes its behavior was determined. A non-linear regression procedure was used to fit four thin layer drying models (Newton, Page, Modified Page 1, and Henderson & Pabis Models). The models were compared with experimental data of onion drying. The adequacy of fit was evaluated using the coefficient of determination (R²), mean bias error (MBE) and root mean square error (RMSE). The R² and RMSE values indicated that the Page model best describe the drying characteristics of onion. It provides a very good theoretical insight for the design of drying equipment needed for the drying of onion slices.