J. Agric. Food Chem. 44 : 2538-2543 (1996)

Role of the Polysaccharide Content and Net Charge on the Emulsifying Properties of b-Lactoglobulin-Carboxymethyl Dextran Conjugates

K. Nagasawa, K. Ohgata, K. Takahashi and M. Hattori

Department ofApplied Biological Science,
Faculty of Agriculture,
Tokyo University of Agriculture and Technology
Tokyo 183, Japan

Beta-Lactoglobulin (BLG)-carboxymethyl dextran (CMD) conjugates were prepared by using water-soluble carbodiimide. Three kinds of CMD differing in molecular weight (40, 70 and162 kDa) were used to investigate the effects of different CMD contents and net charge on the functional changes in BLG. The emulsifying properties of these BLG-CMD conjugates were investigated under various conditions by evaluating the stability of oil/ water (O/W) emulsions prepared with oleic acid and the BLG-CMD conjugates. The emulsifying ability of BLG 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 degree C for 10 min, the emulsifying ability of the BLG-CMD conjugates was higher than that of BLG alone. It is thought that increasing the polysaccharide content and shifting Isoelectric point (pI) of BLG to acidic side by conjugating with CMD of a high molecular weight would be effective to improve the emulsifying properties of BLG under unfavorable conditions.