Covalent interaction of ovalbumin with proanthocyanidins improves its thermal stability and antioxidant and emulsifying activity

Abstract Background The structure of proanthocyanidins (PC) contains a large number of active phenolic hydroxyl groups, which makes it have strong antioxidant capacity. This study investigated the structural and functional properties of ovalbumin (OVA) modified by its interaction with PC. Results It was found that on increasing the concentration ratio of PC to OVA from 10:1 to 40:1, the free amino and total sulfhydryl contents of OVA decreased from 470.59 ± 38.77 and 29.81 ± 0.31 nmol mg −1 to 96.61 ± 4.55 and 21.22 ± 0.78 nmol mg −1 , respectively, and the free sulfhydryl content increased from 7.65 ± 0.41 to 9.48 ± 0.58 nmol mg −1 . These results indicated that CN and CS bonds were formed and PC was covalently linked with OVA. The PC content in the OVA–PC conjugates increased from 281.93 ± 12.92 to 828.81 ± 46.09 nmol mg −1 on increasing the concentration ratio of PC to OVA from 10:1 to 40:1. The contents of α ‐helix and β ‐turn of OVA decreased, and the contents of β ‐sheet and random coil increased, confirmed by circular dichroism. The tertiary structure of OVA was also altered according to the results of fluorescence and ultraviolet absorption spectra. The surface hydrophobicity of OVA–PC conjugates decreased with increasing bound polyphenol content. The conjugation of OVA to PC significantly improved its emulsification and antioxidant activity and denaturation temperature. Conclusion This study may provide valuable information for improving OVA's functional properties and its PC conjugates for applications in the food industry. © 2024 Society of Chemical Industry.