Microencapsulation of liquid lipid with a wall material can suppress its oxidation. Integrated investigation on the mechanism for the suppression revealed that interaction of the lipid with the wall material played an important role. Fatty acids were condensed with hydrophilic food components using immobilized lipase in a water-miscible organic solvent to produce a variety of emulsifiers. It was found that an interaction between water and hydrophilic substrate or between fatty acid and the solvent greatly affected the apparent reaction equilibrium constant. Continuous or semi-continuous reactor systems were also constructed for the production of the emulsifiers on a large scale. The solubility of fatty acids in subcritical water was measured. The measurement brought about a proposal of a novel method for preparing an oil-in-water nano-emulsion.