In general, conching machines are used for mixing and refining a chocolate mass. Such conching machines comprise typically shearing tools extending mainly in radial direction from a rotor arranged in a partially cylindrical trough. These shearing tools have a surface inclined to the trough wall and end often in a relative sharp edge. In this way, they may act in a double manner, i.e. either by shearing chocolate mass off the trough walls when running in one direction, or by providing a rheological shearing effect onto individual layers of the chocolate mass when running in the other direction where the mass is caught in the gap between the trough walls and the converging surface of the shearing tools.
The expenditure for manufacturing such conching machines is considerable, and so are they in operation. For the individual chocolate mass remains in such a conching machine for a long period while mechanical energy is introduced into the mass to bring it from a more or less dry condition to a pasty condition and to make it eventually liquid.
Therefore, attempts have been made to shorten the conching time and/or to replace conching by other processes, or, at least, to simplify the conching process. An increase of introduced energy to shorten the process is, however, not possible to an unlimited extent, because any mechanical energy introduced into the mass converts itself into heat energy, thus heating up the mass. In doing this, there are certain limits not to be exceeded. Heretofore, conching machines were surrounded by an outer tempering or cooling jacket (at the beginning of operation, a conching machine has often to be first to be heated by means of this jacket to soften the chocolate mass. Thus, "tempering" means both heating and cooling)). This jacket provided for heat dissipation during operation, but had, of course, also some limits.