Development of curcumin-loaded nanoemulsion stabilized with texturized whey protein concentrate: Characterization, stability and in vitro digestibility

The impacts of pH (2.8, 4.5, and 7.2) and extrusion cooking temperature (60 degrees C, 85 degrees C, and 110 degrees C) on properties of native whey protein concentrate (NWPC) were evaluated, followed by delivering of curcumin through a nanoemulsion system stabilized with extruded WPC (EWPC). Protein solubility, surface hydrophobicity, and emulsion properties such as emulsion activity index (at 1% [w/w] protein concentration), stability index (at 0.5%, 1%, 2%, and 4% [w/w] protein concentration) and creaming index (evaluated at different protein concentrations [0.5%, 1%, 2%, and 4% w/w] and oil levels [20%, 40%, 60%, and 80%]) were improved as a function of the extrusion process. It was found that both covalent and non-covalent interactions contributed to the stabilization of the extrudates. The rheological investigation of the emulsions stabilized with EWPC (at different oil levels [20%, 40%, 60%, and 80%]) revealed high viscosity and shear thinning behavior as well as much higher G ' and G '' values. Encapsulation efficiency was increased from 90.8% to 95.7% when NWPC and EWPC were used, respectively. The curcumin-loaded nanoemulsion containing EWPC presented high stability in confronting with ionic strength (NaCl salt with a concentration of 0.1-1 M), pH (3, 5, and 7), thermal treatments (pasteurization at 63 degrees C for 30 min and sterilization at 95 degrees C for 10 min) and storage time (1 month at 4 degrees C and 25 degrees C). In vitro release behavior revealed that samples stabilized with EWPC showed burst release in simulated intestine conditions. However, it was more stable in stomach conditions.