Tannic acid-assisted cross-linked nanoparticles as a delivery system of eugenol: The characterization, thermal degradation and antioxidant properties.

Abstract In this paper, eugenol-loaded nanoparticles (sodium caseinate and gum arabic) cross-linked by tannic acid were prepared and characterized. The fourier transform infrared spectroscopy, fluorescence spectrum and circular dichroism confirmed the reaction mechanism between eugenol or tannic acid and protein. Circular dichroism demonstrated that the addition of tannic acid had a great impact on the secondary structure of sodium caseinate. The encapsulation efficiency of eugenol reached 70% and the particle size was about 150 nm. Thermal gravimetric analysis revealed that the degradation temperature of eugenol significantly increased from 77-230 °C to 200-387 °C through the nanoencapsulation. Additionally, the nanoparticles cross-linked by tannic acid remained stable at acidic conditions and after 15 days of storage, and also exhibited slow release and improved antioxidant effects. Therefore, this study provided new insights into the interaction mechanism between polyphenols and proteins, and the possibility of nano-delivering plant essential oils and bioactive molecules using tannic acid as the crosslinking agent.