Methods were modified to improve preparation of αs1- and β-casein from the precipitate obtained when k-casein was prepared by Hill's method. A concentration of 3.3 M urea was used instead of 4.6 M urea to precipitate all the αs1-casein. β-Casein was precipitated from the second-cycle casein fraction P at pH 4.9 as described by others, the gummy precipitate was washed with alcohol, and then air dried. Starch-gel electrophoresis showed that αs1- and β-casein prepared by this method followed by further purification through redissolving and reprecipitating, was essentially free from specific fractions.
1Visiting scholarship under Indo-U.A.R. exchange program at National Dairy Research Institute, Bangalore, India. Present address: Statens Forsøgsmejeri, Hillerød, Denmark.