Development and Performance Evaluation of a Cocoa Bean Sheller cum Winnower

Abstract

Cocoa (Theobroma cacao L.) is a commercial plantation crop in India. It is the main raw material in the production of chocolates, cosmetics, health drinks, pharmaceuticals etc. The cocoa beans which are embedded in a mucilaginous pulp inside the pod consists of two parts- seed coat (shell) and seed cotyledon (nib). Shell is removed from the cocoa bean before or after the seeds are roasted. Shelling is one of the primary processes and critical step in the processing of chocolate or any product that is derived from cocoa beans. It affects the quality of the cocoa nibs in terms of flavour and purity. Shelling of cocoa bean is a very difficult and time-consuming operation. Traditionally, cocoa shelling was done manually or with the help of animals. But nowadays, different shelling machines are available in the industry. The present study focuses on the development of a cocoa bean sheller cum winnower and its performance evaluation in terms of percentage of cracked and uncracked beans, shelling efficiency, capacity, cleaning efficiency and energy requirement. Physical properties viz., shape, size, true density, bulk density, specific gravity etc and optical properties like colour, frictional properties like angle of repose etc. of roasted cocoa beans were examined to design and develop the model. Roasted cocoa beans were shelled using the developed cocoa bean sheller. The shelled cocoa beans underwent winnowing operation by cocoa bean winnower to remove the shells from the nibs, which were later kibbled, ground and pressed to obtain cocoa butter and cocoa powder. The difference in size, shape and the specific gravity of particles were utilised to separate the lighter shell from the nib with the help of a cocoa bean winnower. The actual separation took place in the vertical direction at first by stratification of seeds and second in the horizontal direction by the table motion and gravity. The performance evaluation of the developed machine was carried out using standard methods. Capacity, shelling efficiency, energy requirement, cost of operation of the developed cocoa bean sheller was found to be 155 kg/h, 96%, 0.373kWh and ₹ 76.35/h, respectively. The cleaning efficiency of the cocoa bean winnower was found to be around 89.38% and its cost of operation was estimated as ₹ 82.85/h.