MODELING OF DRYING COCOA BEANS (Theobroma cacao I) AND QUALITY EVALUATION UNDER OPEN SUN AND SOLAR DRYER

Abstract

In this study, thin layer drying experiments were conducted on fermented cocoa beans. An indirect natural convection solar dryer consisting of a solar collector and a drying cabinet was used. Drying under open sun was conducted at the same time for comparison. Loading rate of 2.97, 3.21 and 3.97gicm2 of fermented beans were examined under field conditions of Akure. The drying process took place only in the falling rate period. The drying data were fitted into thirteen (13) different thin layer mathematical models. The result showed that the Verma et. al model was found to be the most suitable model for describing the drying curve of the convective , indirect solar drying process of cocoa beans with R2 = 0.9562,x2 = 0.0069,MBE = 0.0383 and RMSE = 0.0067.while, the Midilli and Kucuk model, best described the drying curve of fermented cocoa beans under open sun with R2 = 0.9866, X2 = 0.0024,MBE = 0.0078 and RMSE = 0.0023.The result from the cut test showed that all the dried cocoa beans falls in the first grade cocoa standard on the international standard which indicates good quality cocoa beans for both solar dryer and sun drying. The chemical assessment test based on pH showed that the beans dried in free convectional indirect solar dryer were of superior qualities with pH values between 5.50- 6.00 against the corresponding values of 4.50-5.00 obtained under open sun drying. Indirect solar dryer is recommended for farmer as it is a cheaper alternative in terms of cost and convenience.