Abstract
κ-Casein can form the complex with β-lactoglobulin by means of heating at 90°C for 10 min in 10 mM imidazole-HCl buffer, pH 7.1, containing 70mM KCl. The complex was dissociated by the addition of 2-mercaptoethanol, while the addition of urea did not affect on the behavior on Sephacryl S-300 gel filtration of the complex. Therefore, the complex formation was confirmed by the Sephacryl S-300 gel filtration with 10mM imidazole-HCl buffer, pH 7.1, containing 70mM KCl and 4.6M urea, and by the sodium dodecylsulfate-polyacrylamide gel electrophoresis in the presence of 2-mercaptoethanol. Effect of carbohydrate moiety of κ-casein was examined by heating at 70°C on the complex formation of β-lactoglobulin with κ-casein components having different sugar contents. It was shown that κ-casein component containing much more carbohydrates formed the complex with β-lactoglobulin easily. This finding may give much information to make clear the function of carbohydrate portion of κ-casein and the mechanism of gelation in long life milk and the utilization of whey proteins in milk industry.
