Mass yield and product crystal size were evaluated in crystallization of anhydrous citric acid on a vibrated bed bath crystallizer, using large number of seed crystals. An operational optimization of the process was investigated by using central composite design (CCD) considering three independent variables: supersaturation level, dimensionless vibration number and crystallization time. The seed population (100,000 units) and operation temperature (55.0 degrees C) were fixed. A condition of maximum yield and mean crystal size of products, 154.8% and 1.105 x 10(-3) m, which were obtained by optimization, have been experimentally tested and resulted in yield and mean crystal size of 178.4% and 1.030 x 10(-3) m. An evaluation of secondary nucleation in the crystallization process was performed in order to monitor possible microstructures present on the surface of crystals or irregular growth of the same, which are caused mainly by high supersaturations that associated with mechanical abrasions that act as nucleation centers. (C) 2011 Elsevier B.V. All rights reserved.