Chitosan can improve the storage stability of ovalbumin fibrils at pH higher than isoelectric point

Food protein fibrils display superior mechanical and interfacial properties compared to the native protein. During processing, protein fibrils are stored for a long time and undergo pH shifts, which accelerate their degradation. In this study, the effects of chitosan on the morphology, structural and rheological properties of ovalbumin (OVA) fibrils after storage at pH higher than isoelectric point were studied. The results showed that OVA fibrils prepared at pH 2.0 remained stable after 7 days of storage. However, after storage at pH 8.0 for 7 days, the turbidity of OVA fibrils increased, the contour length and ThT fluorescence intensity decreased. Furthermore, OVA fibrils became stable again by interacting with chitosan via electrostatic interaction, which was confirmed by zeta potential. In addition, based on the results of Fourier transform infrared spectroscopy, sodium dodecyl sulfide polyacrylamide gel electrophoresis, and fluorescence spectra, it could be concluded that chitosan could interact with OVA fibrils at pH 8.0 during storage. Transmission electron microscope images indicated that the structure of OVA fibrils was maintained by the addition of positively charged chitosan. Finally, the viscosity and storage modulus of OVA fibrils after storage at pH 8.0 increased with the addition of chitosan. These findings implied that OVA fibrils were degraded when stored at pH above isoelectric point, but this degradation could be ameliorated by the addition of chitosan.