Structural modulation of eggshell membrane hydrolysates by tannic acid: Simultaneous enhancement of antioxidant and emulsifying properties

In this study, eggshell membrane hydrolysate (ESMH) and tannic acid (TA) complexes were prepared through both covalent and non-covalent interactions, with their structural properties, antioxidant activity and emulsifying properties being evaluated. The results revealed that the covalent complexes have lower sulfhydryl content (5.3 μmol/g) and higher TA binding capacity (0.15 mg/mL Protein) than the non-covalent complexes at the same TA concentration. FTIR and fluorescence analyses indicated that the structure of ESMH changed after binding with TA. Antioxidant assays demonstrated that TA significantly enhanced the free radical scavenging ability and Fe²⁺chelating ability of ESMH. Furthermore, when the ESMH-TA covalent complex was applied to a storage test of fresh mayonnaise, the rate of lipid oxidation was effectively slowed down. In addition, the covalent complexes successfully prepared emulsions with smaller particle sizes (8.5 μm) and provided improved stability against lipid oxidation by altering the protein conformation.