Abstract: A proteinaceous emulsifier can be obtained by reacting an amino acid ester with a hydrophilic protein in the presence of an endopeptidase to form decomposition products of the hydrophilic protein having a carboxyl end group joined to the amino group of the amino acid ester by amide linkage.This proteinaceous emulsifier has a typical surfactant structure in which a hydrophobic portion consisting of the amino acid ester is attached to the rear end of a hydrophilic portion consisting of the protein, and is characterized by causing little irritation to the skin, exhibiting strong emulsifying power and possessing moisture retention properties. Thus, it is very suitable for use as an emulsifier in various cosmetics such as creams, milky lotions and the like.

Abstract: This invention relates to a cosmetic composition of the oil-in-water type comprising an oily substance having no free carboxyl group, water, and an emulsifier composed of either a combination of a basic polypeptide and a higher fatty acid or a salt (soap) formed from these compounds. This cosmetic composition using such an emulsifier derived from naturally occurring materials causes no irritation to the skin, as contrasted with cosmetic compositions using synthetic emulsifiers. In addition, it shows excellent emulsion stability and storage stability, gives an agreeable feeling, and presents an attractive appearance (fine texture and good gloss).