Influence of the time-temperature-profile during convective and microwave assisted roasting on physical properties of cocoa

The roasting of cocoa is essential for flavor generation and physical properties of manufactured products. Focus of the presented research was to investigate the influence of convective and microwave assisted roasting on physical properties (moisture content & color) of cocoa as well as energy consumption. The investigations were carried out with nibs and beans from Nacional cocoa (Ecuador) roasted with a modular lab roaster. An increase of final cocoa surface temperature during convective roasting and an increase of microwave power at constant final cocoa surface temperature resulted in a decreasing moisture content and an increasing color difference compared to raw cocoa. It was possible to achieve the same physical properties with both roasting types. A simplified calculation of the energy consumption at the different roasting conditions revealed a potential energy reduction by about one third using microwave assisted roasting at slightly lower cocoa surface temperature while obtaining the same physical properties as during convective roasting. Maintaining the physical properties is presumably promoted by the effect that microwave assisted roasting can result in a more homogeneous heating of the whole cocoa.