Thin film evaporation - reduction of conching time  

The cocoa mass as well as the chocolate need a special treatment to reduce the low water content (around 10%) and more important, remove some undesirable flavouring substances. This process basically is part of the conching, that is necessary to redistribute the substances from the dry cocoa into the fat phase creating flavour. Typical conching time in traditional conches is up to three days or even more.

This time consuming step can be reduced by about 60 % using a thin film evaporator in a pre-treatment step. The working principle of thin film evaporators allows the treatment even of very temperature sensitive products. For the thermal separation of a mixture, a thin film is produced at the heated wall of a cylindrical or conical evaporator. A distribution ring on the rotor distributes the liquid evenly across the periphery. Then, the blades fitted at the rotor spread the liquid as a thin film of min. 0.5 mm over the heat transfer surface and form a bow wave, which avoids deposits, intensively mixes the product and finally protects temperature-sensitive products from overheating. The residence time is short and
the product is exposed to elevated temperature only for a very limited time. This working principle provides ideal conditions to reduce the water content and the concentration of undesirable flavours of cocoa mass and chocolate:

• The products can be processed under vacuum, so that temperature can be low, in chocolate production around 50 to
  80°C.
• The water content of cocoa mass is reduced by about 80%.
• The undesired flavours are removed to a minimum.