Milling and micronization of whey protein concentrate (WPC) and zeolite (type clinoptilolite) were carried out. In this work, samples were treated using laboratory equipment for tribomechanical micronization (TMA equipment) at three different rotor speeds. Before and after the tribomechanical treatment, analysis of the particle size and particle size distribution, as well as the specific area, was carried out, in addition to scanning microscopy.A suspension of the investigated materials was treated with ultrasound (1-10 min) immediately prior to determining the particle size distribution.The results showed that the TMA treatment causes a significant decrease in particle size, a change in particle size distribution, and an increase in specific area of WPC and zeolite. These changes in the treated materials depend on the type of the material and the rotor speed of the TMA equipment.The most significant changes in tested materials were observed in samples treated at the maximum rotor speed (22,000 rpm) of the tribomechanical micronization device.As a consequence of the ultrasonic treatment of the suspension of tribomechanically treated WPC, further destruction of partly damaged protein globules occurs. Ultrasonic treatment of the suspension of tribomechanically treated zeolite produced no significant change in its granulometric composition. (C) 2003 Elsevier B.V. All rights reserved.