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

A sodium caseinate (NaCN)–maltodextrin (Md100) conjugate was prepared by a Maillard-type reaction by dry heat treatment of a NaCN–Md100 mixture at 60 °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.