Design and construction of a milling machine for milling of cocoa press cake into micro-particle powders.

Abstract

Cocoa is one of the most important agricultural export commodities in the world and the fundamental ingredient in chocolate manufacture. Cocoa beans are mostly processed into chocolate and cocoa products using a wide range of intermediate products such as cocoa liquor, cocoa butter, cocoa cake and raw cocoa powder. Cocoa powder is obtained by pulverizing the cocoa press cake which remains after the extraction of cocoa butter from cocoa paste and is essentially used in flavouring biscuits, ice cream and other dairy products, drinks and cakes and in the manufacture of coatings for confections and frozen desserts and is also used in the beverage industry. Cocoa powders are increasingly demanded for their prediscussed functions not only as mere powder but rather in a finer form or micro-particle size. The need for micro size milling is because particle size influences many properties of particulate materials like powders, suspensions and is a valuable indicator of quality. The size of powders influences the dissolution property as smaller particles dissolve more quickly and lead to higher suspension viscosities than larger particles. Micro particles are particles with dimensions between 1 * 10 -7 and I * 10—4m. and are obtained by milling using; jet mill, mechanical mills (hammer mills), and stone mills. However stone mills generate considerable heat due to friction which can result in considerable damage to protein and jet mills have lower productivity, large equipment size and high process gas flow. Therefore, the objective of this study was to design and construct a milling machine for milling of cocoa press cake into micro particle powder and that is locally available- The methods used for achieving the objective were making engineering drawing of the parts, fabricating the parts and their assembly to form the complete machine. The designed cocoa press cake milling machine was constructed, tested with the milling efficiency of 79.5% and loss of 20-5%, through put of 34.5kg/hr- It can be used by local entrepreneurs for running a business and to earn a living from it.