Energy reduction during chocolate conching using a reciprocating multihole extruder

Chocolate consists of finely ground sugar, milk powder and cocoa, which must be mixed with cocoa butter, to obtain the final product. The mixing of the chocolate takes place within the 'conche' although this is not an efficient part of the chocolate making process, as it is both time and energy consuming. The complexity of conching is due to the number of physical constraints that must be achieved, such as the breaking of agglomerates, the coating of particles with fat, reduction in viscosity, elimination of undesirable volatiles and final flavour development. As an addition to the conche, a 'reciprocating multihole extruder' (RME) was used within this study to pre-mix the chocolate before further processing within a 'Kemutec' mixer. The Kemutec mixer was used in order to simulate the typical mixing characteristics that occur in a traditional conche. Efficiency was then compared to mixing in the Kemutec mixer alone, without a pre-mix. Results showed that the RME could quickly reduce the viscosity of the chocolate whilst at the same time consuming little energy. In addition, the RME also reduced the energy required for further processing in the Kemutec mixer. An analysis of experimental data showed that these benefits resulted in an energy saving of up to 32% when the RME was used prior to Kemutec mixing. (C) 2003 Elsevier Science Ltd. All rights reserved.