The efficient dispersion of powders in liquids is required in many fields. For this reason, it is useful to understand the mechanisms of dispersion and the physical properties of powders which influence the dispersion rate. Here, we have chosen to work with a low-fat cocoa powder commonly used in the food industry. Firstly, we have determined the physical properties of the powder (densities, cohesion, flowability, size and surface energy) and then measured the dispersion times of cocoa in water using a novel optical method. Further experiments, using the same technique, are performed using larger grains obtained by granulating cocoa powder. It is found that the dispersion times are shorter for the granules and much shorter than the dispersion time for ungranulated powder. The dispersion times for granules increase with the size of granules.