Preparation, characterisation and selected functional properties of sodium caseinate–maltodextrin conjugates

Sodium caseinate (NaCN)–maltodextrin (Md40 or Md100) conjugates were prepared by a Maillard-type reaction by dry heat treatment of mixtures of NaCN and Md at 60 °C and 79% relative humidity for 4 days. Minimal levels of coloured reaction products were formed during conjugate preparation. Conjugation resulted in a 35.6% and a 36.2% loss of available amino groups in the NaCN, and a 17.8% and a 25.7% loss of available reducing groups in Md40 and Md100, respectively. SDS–PAGE and gel permeation chromatography confirmed conjugation. When assessed in the pH range 2.0–8.0 at 20 °C and 50 °C, conjugates had improved solubility compared to NaCN, particularly around the isoelectric point of the protein. The emulsifying properties of NaCN–Md conjugates were assessed in oil-in-water (o/w) emulsions and in model cream liqueurs. The conjugate stabilised o/w emulsions and liqueurs showed improved stability when compared to NaCN stabilised o/w emulsions and liqueurs. These results indicate a potential for these NaCN–Md conjugates as speciality functional food ingredients.