Fabrication of pea protein isolate-folic acid conjugates via free radical grafting: Formation mechanism, stability, and curcumin delivery potential evaluation

Plant proteins are increasingly used to encapsulate hydrophobic nutrients to formulate functional foods. A major challenge for plant protein-based nanocarriers is to improve the solubility and stability, thereby enhancing the absorption efficiency and bioavailability of hydrophobic nutrients within them. To address this issue, a free radical grafting strategy of folic acid (FA) modified pea protein isolate (PPI) was developed. The FA loading capacity of PPI-FA conjugates was 2.1-fold higher than that of PPI-FA mixtures. Conjugation of FA improved the solubility, thermal stability and storage stability of PPI. The photostability of FA was also enhanced (retention rate increased from 75.76 % to 94.92 %). Complexation with PPI-FA conjugate elevated the solubility, anti-cancer activity and cellular uptake of curcumin (Cur). The bioavailability of PPI-FA-Cur was 63.27 %, far exceeding those of free Cur (6.95 %) and PPI-Cur (24.47 %). These findings expand PPI's application and provide new reference for the development of advanced food delivery systems.