Role of the polysaccharide content and net charge on the emulsifying properties of beta-lactoglobulin-carboxymethyldextran conjugates

beta-Lactoglobulin (beta-LG)-carboxymethyldextran (CMD) conjugates were prepared by using water-soluble carbodiimide. Three kinds of CMD differing in molecular mass (40, 70, and 162 kDa) were used to investigate the effects of different CMD contents and net charge on the functional changes in beta-LG. The emulsifying properties of these beta-LG-CMD conjugates were investigated under various conditions by evaluating the stability of oil/water emulsions prepared with oleic acid and the beta-LG-CMD conjugates. The emulsifying ability of beta-LG was greatly improved by conjugating with CMD in the acidic pH range in the presence of less than 0.5 M NaCl. After heating at 80 degrees C for 10 min, the emulsifying stability of the beta-LG-CMD conjugates was higher than that of beta-LG. It is thought that increasing the polysaccharide content and shifting the isoelectric point of beta-LG to the acidic side by conjugating with CMD of a high molecular weight would be effective in improving the emulsifying properties of beta-LG under unfavorable conditions.