ABSTRACT Protein‐polyphenol conjugates have gained attention as antioxidant emulsifiers, yet their performance in diverse food systems with different pH conditions remains limited. This study investigated the structural characteristics of pea protein isolate (PPI) bound with different levels of tannic acid (TA), and their applicability as protein‐based antioxidant emulsifiers in oil‐in‐water emulsions at pH 3 and pH 7. The structural modifications of PPI by TA addition were confirmed using Fourier‐transform infrared (FTIR) spectroscopy and surface hydrophobicity, resulting in a change in emulsifying performance. At pH 3, the surface charge of oil droplets in PPI‐TA‐stabilized emulsions was close to zero, suggesting that steric repulsion played a predominant role in emulsion stability. At pH 7, all emulsions stabilized with PPI or PPI‐TA exhibited negatively charged droplets, suggesting that both electrostatic and steric repulsion contributed to emulsion stability. The DPPH inhibition of PPI‐TA increased with higher TA concentration used, whereas the Fe 2+ chelating activity decreased beyond a certain TA concentration, indicating that a proper balance between polyphenol and protein is essential for effective antioxidant emulsifiers. Overall, the fabricated PPI‐TA exhibited comparable physical and chemical stability to PPI while providing additional antioxidant activity, highlighting the potential of protein‐polyphenol as antioxidant emulsifiers in food‐grade emulsion systems.
Gong et al. (2026) studied this question.