The flux behavior of ceramic and polysulfone membranes was examined during cross-flow ultrafiltration (UF) of depectinized pineapple juice. The effects of transmembrane pressure (TMP) and temperature on membrane fouling have been evaluated. The observed flux decay was modeled using a modified form of the differential equation used to describe classical dead-end filtration process. The mechanism of fouling during the cross-flow ultrafiltration was identified by estimation of the parameters model according to a nonlinear regression optimization procedure. Analysis of the results revealed that hollow fiber membrane separation process is controlled by a cake filtration mechanism and a pore blocking fouling mechanism controls ceramic tubular membrane. The model parameter k was modeled as a temperature and transmembrane pressure function for each combination juice-membrane. The main physical chemistry properties of pineapple juice were evaluated in order to determine the condition that supply the highest permeated flux and best clarified juice. (C) 2003 Elsevier Science B.V. All rights reserved.