Journal on Processing and Energy in Agriculture (Jan 2011)
Agglomeration of cocoa powder mixtures: Influence of process conditions on physical properties of the agglomerates
Abstract
Nowadays agglomerated cocoa drink powder represents a very appealing beverage for children as well as for adult customers. It is produced by mixing basic ingredients (cocoa powder, sugar, vitamin and lecithin, which is followed by agglomeration. Agglomeration is necessary, because non-agglomerated cocoa powders exhibit very poor flow and reconstitution properties. This research showed the influence of process conditions and composition of the cocoa powder mixtures on the physical properties of the agglomerated final product. Eight mixtures were prepared, four containing cocoa powder with 10-12% fat and four containing cocoa powder with 16-18% fat. Three different kinds of sugars (sucrose, glucose and trehalose) and a sweetener (erythritol) were added to cocoa powder while preparing the mixture. Agglomeration was conducted using STREA 1TM fluid bed agglomerator at a constant air temperature (60°C), with a constant addition of water soluble lecithin (Metarin®) with varying duration of the process and varying amount of added water. Bulk density (Engelsmann jolting volumeter), particle size (Malvern Mastersizer 2000) and colour measurements (Minolta colorimeter; L = brightness, a = redness, b = yellowness) were conducted prior to and post agglomeration, while agglomerate hardness was estimated by conducting a compression test with a 30 mm probe on TA.HDPlus Texture Analyser. Percentage of added water had a significant effect on colour, bulk density and the duration of the agglomeration process. This effect was more significant with mixtures made with cocoa powder containing 10-12% fat. As for mixtures with 16-18% fat, a significant influence of water addition on agglomerate median diameter was found. Agglomeration time and the percentage of added water showed dependence towards the composition of the mixture. This research showed that, in order to agglomerate powder mixtures successfully, parameters such as mixture composition, particle size, percentage of added water and lecithin, drying temperature, process duration and ambient conditions should be well coordinated and controlled to get agglomerates with optimal quality.
