Dual functionality of phosphates in a micellar casein concentrate: reconstitution enhancement while tailoring...

We investigated how dipotassium hydrogen phosphate (DKP), trisodium citrate (TSC), and sodium tripolyphosphate (STPP) at 0-60 mEq/L regulate the reconstitution and glucono-δ-lactone (GDL)-induced gelation of 10 % (w/w) micellar casein concentrate (MCC). Phosphates markedly improved redispersibility, as quantified by the dispersible protein fraction: from 45 % (water) to 97 % with STPP at 20 mEq/L; DKP and TSC reached 88-90 % at 60 mEq/L. In parallel, colloidal restructuring-evidenced by a smaller hydrodynamic diameter, lower polydispersity index, decreased turbidity, and higher surface hydrophobicity-translated into stronger acid gels. STPP had the greatest effect: the maximum storage modulus (G') increased from 2.6 × 10³ to 2.8 × 10⁴ Pa, gel hardness increased from ∼180 to 2.35 × 10³ N, and water-holding capacity increased from ∼20 % to >92 % (30-60 mEq/L). Low-field nuclear magnetic resonance (LF-NMR) indicated the conversion of intermediate/free water into more tightly bound states, whereas Fourier transform infrared (FT-IR) spectroscopy suggested strengthened hydrogen-bonding and ion-dipole interactions within the protein matrix. Overall, phosphate identity and concentration (STPP > TSC > DKP) provide a tunable route to simultaneously enhance MCC reconstitution and engineer acid-gel textures.