Investigation into the physical and chemical properties of sodium caseinate-maltodextrin glyco-conjugates

Casein-maltodextrin glyco-conjugates were prepared using an economical, food-grade process based on the Amadori re-arrangement of the Maillard reaction. The resultant glyco-conjugates were slightly yellow in colour and the degree of discolouration was dependent on heating time. Formation of glyco-conjugates was demonstrated by determining the reduction of free amino-groups by the O-phthaldialdehyde (OPA) assay and sugar reducing ends by gas chromatography-mass spectrometry (GC-MS). Increases in molecular weight were monitored by SDS-polyacrylamide gel electrophoresis (PAGE) and were in agreement with those predicted for the conjugation of casein monomers with malto-oligosaccharides of average DP 7-10. 2D-Urea-SDS-PAGE demonstrated that both protein and saccharide components co-migrate, indicating that covalent bonds were upon heating. This resulted in increases in mass-to-charge ratio of the materials, which suggested decreases in pI. These observed chemical and physical changes were reconciled with previously documented improvements in emulsifying properties.