Protease-antiprotease balance is involved in a number of biological and pathological processes and in egg white, proteases are thought to have role in embryogenesis and antimicrobial defense. Other biological activities associated with egg white include immunomodulatory, anti- cancer, antioxidant and anti-hypertensive properties. The avian egg is an important source of nutrients, containing all of the proteins, lipids, vitamins, minerals and growth factors required by the developing embryo Ovomucoid, a serine protease inhibitor, is useful in oral delivery of protein/ peptide therapeutics. Co-administration of ovomucoid with calcitonin, is often used in the management of osteoporosis. Because ovomucoid inhibits digestive enzymes, such as trypsin, a- chymotrypsin and elastase, it has been found to improve the oral delivery of insulin. In view of its various important roles, ovomucoid was isolated from duck and its third domain was characterized. The present study highlights the characterization of chemicallymodified third domain.