Heat stability and freeze-thaw stability of oil-in-water emulsions stabilised by sodium caseinate-maltodextrin conjugates

A sodium caseinate (NaCN)-maltodextrin (Mc1100) conjugate was prepared by a Maillard-type reaction by dry heat treatment of a NaCN-Md100 mixture at 60 degrees C and 79% relative humidity for 4 days. Conjugation resulted in a 35.7% loss of available amino groups in the NaCN and a 25.9% loss of available reducing groups in the Md100. The crude conjugate was purified by batch anion exchange chromatography to remove non-conjugated Md100. Purification reduced the available reducing groups in the conjugate from 74.1% to 23.7% and increased the protein content from 45.6% to 83.9%. The emulsifying properties of the conjugates were assessed in oil-in-water (o/w) emulsions: crude and purified conjugate stabilised emulsions had improved storage stability and freeze-thaw stability when compared to NaCN stabilised emulsions. Purified conjugate stabilised emulsions had better thermal stability than NaCN, NaCN-Md mixture and non-purified conjugate stabilised emulsions. These results indicate a potential for these NaCN-Md conjugates as speciality functional food ingredients. (C) 2009 Elsevier Ltd. All rights reserved.