It is necessary to reduce the size of the particles to ensure that the consumer of the chocolate does not perceive any separate coarse particles in the mouth. Chocolate with particles larger than the required fineness of 25-30mm will taste gritty to the consumer. Chocolate may vary in fineness, depending on the manufacturer, and the application required.
Highly intensive grinding methods ensure a large amount of very fine particles, but also there can be a number of technological consequences:

• the smaller the particle size, the higher the energy consumption;
• further particle size reduction changes the texture and makes the chocolate
  clay-like;
• further particle size reduction also increases the total surface of the particles
  per unit of weight; extra fat, for instance, cocoa butter or milk fat, must be added to cover or lubricate this larger surface to obtain the same rheological properties.

A well-refined product contains only very few coarse particles and not too many fine particles. Practice has shown that the best particle size distribution can be obtained by roll refining, using either a one-roll or a two-roll system.