Preparation optimisation and storage stability of nanoemulsion-based lutein delivery systems

The present work formed lutein-enriched nanoemulsions stabilised by sodium caseinate (SC) using a high-pressure homogenisation process, and the influence of environmental conditions on the physicochemical stability of the nanoemulsion was investigated. The results showed that the droplet diameter of the nanoemulsion was largely dependent on homogenisation conditions. Optimum results were obtained for 1.0% (w/w) SC, 100 MPa pressure, and 7 homogenisation cycles, which produced a nanoemulsion with a mean droplet diameter of 234.01 ± 3.40 nm, polydispersity index of 0.123 ± 0.028, and zeta potential of −36.56 ± 1.51 mV. The nanoemulsion remained physically stable after a 30 d storage at 4 °C, and the chemical degradation rate of lutein was considerably decreased. Thermal treatment at 60–100 °C had little effect on its physicochemical stability; conversely, pH, ionic strength (NaCl or CaCl2), concentration treatment, and freeze–thaw cycling had major impacts on the physicochemical stability of nanoemulsion.