Concentration-dependent ion-specific amyloid fibrillation of Phaseolus vulgaris protein for dysphagia-oriented...

Fibrillation of plant proteins to enhance their gel properties has potential in the development of texture-modified protein gel foods. In this study, various concentrations (12.5-150 mM) of divalent mineral ions (Ca²⁺, Fe²⁺, and Zn²⁺) were used for regulating the aggregation behaviour of black kidney bean protein fibrils (BKPFs). The rheology, water-holding capacity, and microstructure of BKPF hydrogels were investigated. The addition of Ca²⁺ and Zn²⁺ to BKPFs promoted fibril formation and entanglement, with the BKPFs forming a denser gel network at low ion concentrations (12.5-50 mM). However, excessive electrostatic shielding induced random particle aggregation at higher Ca²⁺ and Zn²⁺ concentrations (>100 mM), producing disordered gel networks. The addition of Fe²⁺ inhibited the fibrillation and aggregation of the BKPFs. The results of X-ray photoelectron spectroscopy (XPS) and molecular interaction revealed that the mineral ions coordinated with the BKPFs, strengthening the hydrogen bonds and hydrophobic interactions. The addition of the optimal concentrations of mineral ions substantially increased the self-supporting ability, storage modulus, and water-holding capacity of the gels and decreased the critical strain and creep recovery. The mineral ion-BKPF composite gel met the level 4-5 International Dysphagia Diet Standardization Initiative (IDDSI) requirements. The study findings provide theoretical insights into the role of divalent ions in modulating the fibrillation and gelation of plant proteins and support the development of nutritious, easy-to-swallow foods for managing dysphagia.