THE DRYING KINETICS AND POLYPHENOL DEGRADATION OF COCOA BEANS

This study investigated the kinetics of drying and polyphenol degradation during hot air and sun drying of cocoa beans. Hot air drying was carried out using a constant humidity-controlled (50% relative humidity) oven at temperature range of 60-80C, and sun drying was carried out by exposing the beans under direct sunlight. Several semi-theoretical models were used to model the kinetics of moisture diffusion and it was found that the Page and Logarithmic models were able to provide good prediction. A first-order reaction kinetics was used to predict the polyphenol degradation process with rate constants ranging from 0.011/h to 0.052/h. Activation energy for polyphenol degradation was determined at 8.97 kJ/mol using the Arrhenius equation. Effective diffusivity during drying was found within the order of magnitude (10(-12)-10(-10) m(2)/s) reported in most drying literatures. PRACTICAL APPLICATIONS The understanding of moisture diffusion is important in dryer design especially in the determination of effective diffusivities during drying. Polyphenols are important antioxidants that are beneficial to human health. By investigating the polyphenol degradation kinetics, this helps to link the reactions with moisture diffusion kinetics.