Effect of Drying Temperature and Drying Air Velocity on the Drying Rate and Drying Constant of Cocoa Bean

Abstract

The effect of some drying parameters and drying conditions of cocoa bean were determined. Three levels of temperatures (55, 70 and 81 °C) and three air velocity levels (1.3, 2.51 and 3.7 m/s) were used in the presented study. The moisture content of the cocoa bean used was 79.6 % (db). The heated batch cocoa bean dryer used in the evaluation was successful in drying thin layer of cocoa bean 5 cm deep at initial moisture content of 79.6 % (db) to 6 % (db), in 4-6 h of continuous drying at the above mentioned temperature range. The drying constant ranged from 0.009583 h^-1 to 0.12666 h^-1 under the above drying conditions. Coefficient of determination of 84.8 % was obtained with relationship of temperature and drying constant but when air velocity was incorporated it decreased to 80.9 %. The drying rate increased with increase in temperature and air velocity but decreased with time. The dryer can remove an average of 4.66 kg of water per day at 55-81 °C and air velocity of 1.3 m/s while at 2.51 m/s it can remove an average of 5.3 kg of water per day under the same drying conditions.