Combining different ionic polysaccharides and pH treatment improved functional properties of soybean protein amyloid fibrils through structural modifications

This paper reported the effects of different ionic polysaccharides (a cationic polysaccharide (chitosan, CTS), an anionic polysaccharide (high methoxyl pectin, HMP), and a neutral polysaccharide (dextran, DEX)) and pHs (2.0, 4.5, 7.0, and 9.0) on the structural and functional properties of soybean protein amyloid fibrils (SAF) under non-covalent interactions. The fluorescence spectroscopy, ζ-potential, surface hydrophobicity (H0), and turbidity analyses revealed that, at any pH, HMP had a greater effect on the structure of SAF than CTS or DEX. Electrostatic and hydrophobic interactions predominated between SAF and HMP. The addition of negatively charged HMP prevented the exposure of hydrophobic groups, the H0 and ζ-potential decreased. Moreover, compared to SAF, the rheological properties of SAF-HMP complexes were enhanced. In particular, at pH 2.0, HMP was crosslinked with SAF and changed the fibrils conformation, the foaming stability of SAF-HMP increased to 100%. Furthermore, at pHs 2.0 and 4.5, strong electrostatic repulsion occurred between CTS and SAF. Therefore, SAF-CTS exhibited the highest emulsifying activity index and emulsifying stability index, which are 58.21 m2/g and 41.76 min, respectively, followed by SAF-HMP. By contrast, DEX had the least influence on the fibrils. These results will give a hand for industrial production of soybean protein amyloid fibrils.