Interaction of ovalbumin with lutein dipalmitate and their effects on the color stability of marigold lutein esters extracts

• The color stability of lutein esters was improved by OVA during storage and light. • Changes in secondary and tertiary structure of OVA were observed. • Lutein dipalmitate quenched the intrinsic fluorescence of OVA in a static manner. • Lutein dipalmitate bound to OVA by van der Waals force and hydrogen bond. In this study, the interaction of ovalbumin with lutein dipalmitate and the effect of ovalbumin on marigold lutein esters extracts were investigated. Lutein dipalmitate quenched the fluorescence of ovalbumin by static quenching. Binding and thermodynamic parameters proved that lutein dipalmitate bound to ovalbumin spontaneously by van der Waals force and hydrogen bond, and the complex stoichiometry was 1:1. Through three-dimensional fluorescence spectroscopy, Fourier transform infrared spectroscopy and circular dichroism experiments, the conformation of ovalbumin was unfolded, and alteration in the ovalbumin secondary structure induced by lutein dipalmitate was observed. The results of transmission electron microscopy and particle size revealed that there were spherical and nano-sized aggregates in the ovalbumin-lutein dipalmitate system, indicating the lutein dipalmitate not only could bind to ovalbumin at molecular level, but also promote the aggregation of ovalbumin. Additionally, the addition of ovalbumin had a positive effect on the stability of marigold lutein esters extracts.