Catalase was immobilized in alginate capsules (diam. 2, 4 and 8 mm) and used for decompn. of H2O2 in its aq. solns. (pH 5.5-8.0, 10-40 degrees C). The decompn. kinetics was described by the 1-st order model The substrate concn. ratio (inside of the capsule and on its surface) decreased strongly with increasing Thiele module. The optimum process parameters (pH 6-8, temp. 24-35 degrees C) were recommended for the H2O2 removal after pasteurization of milk.