Improvement of process parameters and evaluation of milk chocolates made by the new coarse conching process

Abstract

Chocolate mass is produced by roller refining and downstream conching or alternatively by ball milling. The latter requires high fat contents; water and off-flavours cannot be volatilized as in classical dry conching. To overcome this, coarse conching is performed first, applying the high shear vortex chamber built into the kneading zone. It does not only intensifies energy and mass transfer, but also reduces particle size of crystal sugar. Finally, grinding is done downstream. Only some examples from the extensive initial development phase are shown, e.g. on the behaviour of skim and whole milk powder. During process optimization, three variables were combined with two full factorial experimental designs carried out using differently scaled ball mills. The resulting flow properties of the samples were combined in model equations. All results showed evidence that during grinding, the lecithin must be added as late as possible in order to achieve low viscosities over the entire flow curve. Using smaller grinding balls resulted in higher yield values, but lower viscosities at higher shear. Intensive extra shear after industrial-scale milling had little impact, but did resulted in lower viscosities at high shear after using the pilot-scale mill. After finding optimized settings, confirmation trials were run allowing reduced energy consumption by the vortex chamber. Evaluation of sensory perception showed cocoa taste to be more intense in samples from the coarse conching process when compared to the conventional process. Finally, the results allowed line set-ups for small scale as well as for continuous large-scale production.