MOISTURE DESORPTION ISOTHERMS OF COCOA BEANS

Moisture desorption isotherms (ERH-EMC) of cocoa beans were determined using a constant environment chamber for various combinations of air relative humidity (30 to 90%) and temperature (20 degrees to 70 degrees C). The sigmoidal desorption isotherms show that moisture is being adsorbed in multilayers and that the cocoa beans are macroporous. The new modified Hasley, Henderson, and Chung equations whose parameters are fitted to a fifth-order polynomial with respect to temperature, can be used to represent the desorption isotherms of cocoa beans satisfactorily in the temperature range investigated. All three equations fitted the data better at low and high temperatures than at the middle of the range (40 degrees to 60 degrees C). This is most probably due to the evaporation of volatile material and significant chemical reactions and enzymatic activities at those temperatures.