The clotting and stabilization of milk were studied by using proteolytic enzymes immobilized onto resinous material Milk coagulation was studied in a fluidized-bed reactor. The effect of the concentration of enzyme as well as the cross-linking agent and pH of the coupling medium on the immobilization of enzymes was studied. Immobilized proteolytic enzymes showed improved thermal and chemical stability, for SRF-pepsin and SRF-trypsin. The maximum retention activity occurred between 30 and 40 degrees C. In the study of the effect of the pH of the coupling medium on the extent of coupling of enzymes, it was observed that coupling of trypsin and chrymotrypsin was critically dependent on the pH of the medium, whereas pepsin shows less critical behaviour within the pH range 2-4. The calculated apparent Michealis constants K-m for immobilized pepsin, chymotrypsin and trypsin were 0.76 mu g, 0.66 mM, and 0.03 mM, respectively. The operational half-life ofthe systems was from 15 to 22 days.