The results of a study of the enzymatic hydrolysis of sunflower oil are presented. The influence of the enzyme and substrate concentrations has been investigated. The interfacial area was modified by changing the volume fraction of oil, while keeping other variables constant. A phase inversion is indicated, which influenced the reaction kinetics by the possible formation of enzyme multilayers, because of steric hindrance. By means of the initial hydrolysis rate, the lipase concentration for achieving interface saturation was estimated. A Lewis cell type contactor was used for the determination of the interface surface, and droplet diameters were deduced.