Effects of rosmarinic acid covalent conjugation on the allergenicity and functional properties of egg white protein

Polyphenols can form complexes with proteins, potentially enhancing the properties of egg white protein (EWP) by altering its structure. This study aimed to explore the effect of covalent conjugating with rosmarinic acid (RA), a bioactive polyphenol found in various edible Lamiaceae herbs, on the structure, allergenicity, and functional properties of EWP. The successful preparation of EWP-RA conjugates was confirmed through RA binding equivalent analysis. Fluorescence spectroscopy, Fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD), and ultraviolet (UV) absorption spectroscopy collectively indicated that the covalent conjugation with RA led to significant structural alterations in EWP. Furthermore, the conjugation of RA markedly enhanced the antioxidant capacity of EWP, as evidenced by its improved ability to scavenge DPPH and ABTS + radicals. Enzyme-linked immunosorbent assay (ELISA) results indicated a substantial reduction in the binding capacity of EWP-RA conjugates to IgG and IgE, indicating a decrease in the allergenic potential of EWP. Moreover, the incorporation of RA was associated with an increase in the absolute zeta potential, protein flexibility, and free sulfhydryl content of EWP, alongside a reduction in surface hydrophobicity. The findings also revealed that RA enhanced the emulsifying activity, emulsion stability, foaming ability and foaming stability of EWP. Furthermore, the storage performance of EWP improved after conjugation with RA. In conclusion, the covalent conjugation of EWP with RA not only diminished its allergenic potential but also improved its functional properties through structural modification. This study posits that such an approach could be an effective strategy for enhancing the functional properties of EWP while concurrently mitigating its allergenic potential, thereby offering promising applications in the formulation of future food products.