Thin layer drying characteristics of alligator pepper, ginger and turmeric

The delightful pungency, aromatic compounds and phytochemicals in some spices make them indispensable in local food systems and native medicine, hence, driving a robust market in many parts of the world. The understanding of their drying characteristics is very important for processing and adding value, and a thin layer drying study is a proven method for achieving this. In this study, changes in the moisture content, moisture ratio, drying rate and effective diffusivity of alligator peppers, ginger and turmeric were investigated at three drying temperatures 50, 60, and 70 °C following standard procedures. Five models were proposed to simulate the drying process. Non-linear regression was used to establish the coefficient of determination (R2), sum of square error (SSE) and root mean square error (RMSE) for each model to determine the model of the best fit. The Page model gave the best fit for ginger while the logarithmic model was best fitted for alligator peppers and turmeric. The effective diffusivity ranged from 1.79-3.08 × 10-9, 8.44-9.74 × 10-9, and 4.06-6.49 × 10-9 m2.s-1 for alligator peppers, ginger and turmeric, respectively. The activation energy ranged from 16.5-22 kJ.mol-1.K-1 for the three spices. These findings promise improvement in the drying, processing and handling of spices, thereby boosting the obtainable income from the value chain.