Understanding of physicochemical properties and antioxidant activity of ovalbumin-sodium alginate composite nanoparticle-encapsulated kaempferol/tannin acid.

In this research, ovalbumin (OVA) and sodium alginate (SA) were used as the materials to prepare an OVA-SA composite carrier, which protected and encapsulated the hydrophobic kaempferol (KAE) and the hydrophilic tannic acid (TA) (OVA-SA, OVA-TA-SA, OVA-KAE-SA, and OVA-TA-KAE-SA). Results showed that the observation of small diffraction peaks in carriers proved the successful encapsulation of KAE/TA. The protein conformation of the composite nanoparticles changed. OVA-TA-SA composite nanoparticles had the highest α-helix content and the fewest random coils, so the protein structure of it had the strongest stability. OVA-TA-KAE-SA composite nanoparticles had the strongest system stability and thermal stability, which might be due to the synergistic effect of the two polyphenols, suggesting the encapsulation of KAE/TA increased the system stability and the thermal stability of OVA-SA composite nanoparticles. Additionally, the composite nanoparticles were endowed with antioxidant ability and antibacterial ability (against Staphylococcus aureus and Escherichia coli ) in the order OVA-TA-SA > OVA-TA-KAE-SA > OVA-KAE-SA based on the difference in antibacterial diameter ( D , mm) and square ( S , mm 2 ), indicating that polyphenols enhanced the antibacterial and antioxidant ability of OVA-SA composite nanoparticles, and the enhancement effect of TA was stronger than that of KAE. These results provide a theoretical basis for the application of OVA-SA composite nanoparticles in the delivery of bioactive compounds.