Stable complex of sodium caseinate and hexaglycerol monooleate with improved oil-in-water emulsion stability and curcumin encapsulation

To improve the emulsifying property of sodium caseinate (NaCas) as stabilizer of oil-in-water emulsions and encapsulation of bioactive compounds, three hexaglycerol mono-fatty acid esters were chosen as small molecular weight surfactants to complex with NaCas. Hexaglycerol monooleate (HGMO) was found to be the optimal surfactant and the optimal mass ratio was 1:1, through characterization of particle size, Zeta-potential, and turbidity. Fluorescence and FTIR spectra indicated that the hydrophobic interaction and hydrogen bond provided driving forces to the formation of stable complex. The complexation of HGMO to NaCas increased the surface hydrophobicity and decreased surface tension compared with NaCas, and strengthened the EAI and ESI. The NaCas-HGMO complex had good stabilization on rice bran oil-in-water emulsions, in a wide pH and ionic strength, and the forwarding Cur encapsulation in O/W emulsions dramatically reduced the degradation during storage at 4℃. Therefore, the present NaCas-HGMO complex might be employed as an effective emulsifier to stable O/W emulsions that load lipophilic bioactives in functional foods or beverages.