Comparison of legume and dairy proteins for the impact of Maillard conjugation on nanoemulsion formation, stability, and lutein color retention

While dairy proteins have traditionally been used to stabilize nanoemulsions, there is a trend towards plant-based formulations. Additionally, both types of protein are poorly soluble near their isoelectric point. The main goals of this research were to develop and characterize Maillard conjugates from pea protein (PPI) or caseinate and dextran, and to evaluate the physical stability of nanoemulsions made with such emulsifiers at various ionic strengths, pH = 4.6, and temperatures during storage, as well as lutein color retention over storage. Protein conjugates formed nanoemulsions with diameters of 125 ± 12 nm (PDI = 0.13 ± 0.00) and 269 ± 36 nm (PDI = 0.76 ± 0.42) (pH = 7) for caseinate and PPI, respectively. Conjugation improved the physical stability (droplet size) of emulsions at the isoelectric point, during storage at 4–55 °C, and in ionic solutions. Lutein color degradation was better associated with particle size than conjugation and was lowest for PPI-stabilized emulsions. This study suggests that Maillard conjugation could improve PPI emulsification properties.