Theoretical Analysis and Experimental Investigation of a Small-Scale Centrifugal Cocoa Bean Cracker

Efficient separation of cocoa shell and kernel is a critical operation in semi-finished cocoa processing, where conventional mechanical methods such as grinding, cutting, and rubbing often generate excessive heat, leading to cocoa butter melting and degradation of kernel quality due to its high fat content. To overcome these limitations, this study pro-poses a dynamic impact-based framework for a small-scale centrifugal cracking system, in which fracture is induced by controlled kinetic impact rather than compressive loading. A combined theoretical and experimental investigation was conducted on roasted cocoa beans at a small industrial scale. Mechanical characterization showed that the mean and maximum shell fracture forces were 23.515 N and 54.382 N, respectively, while kernel fracture forces were significantly higher at 91.896 N and 195.327 N. A dynamic analysis of the centrifugal cracker identified a critical rotational speed range of 812–975 rpm, corresponding to impact velocities of 17.14–20.57 m/s and kinetic energies of 0.17–0.25 J per bean. Experimental validation indicated an optimal operating range of 860–900 rpm, achieving less than 1.1% uncracked beans and less than 2% fine nibs (<3 mm). Below 800 rpm, incomplete cracking was observed, whereas speeds above 950 rpm increased kernel fragmentation. These results demonstrate that precise control of impact energy is the key factor governing efficient centrifugal cracking performance in cocoa processing.