Structural Characterization of Sodium Alginate-Albumen Gel Beads and Their Fe³⁺ Loading Performance

To develop a novel carrier for mineral delivery, sodium alginate-albumen composite gel beads (SA-A) were prepared using sodium alginate and albumen as substrates, and further iron-loaded composite gel beads (SA-A-Fe) were synthesized. The physicochemical properties and Fe³⁺ loading capacity of the beads were evaluated through structural characterization. Results revealed that the binding between sodium alginate and albumen was governed by non-covalent interaction. Compared to pure sodium alginate beads (SA), the SA-A beads exhibited markedly enhanced viscoelasticity and thermal stability, with both viscoelastic and thermal properties further improved upon Fe³⁺ loading. The adsorption of Fe³⁺ was more in line with the pseudo-second-order kinetic model, indicating that chemisorption could be considered as the dominant mechanisms of Fe³⁺ adsorption. In the first adsorption stage of the intraparticle diffusion model, the rapid diffusion of Fe³⁺ from the aqueous phase to the bead surface was identified as the rate-limiting step, followed by gradual intra-particle diffusion until equilibrium was attained. The adsorption process was characterized by heterogeneous surface sites and multilayer adsorption behavior. In vitro release studies demonstrated that the SA-A bead, as a wall material, effectively delayed premature Fe³⁺ release in simulated gastric fluid while promoting sustained release under simulated intestinal conditions, demonstrating that the SA-A-Fe gel beads possess unique sustained-release characteristics and good stability. Collectively, these findings demonstrate that SA-A beads possess excellent structural integrity and high Fe³⁺ loading efficiency, with controlled iron ion release under simulated gastric and intestinal fluid conditions, highlighting their promise as an effective carrier for iron delivery. This work provides a scientific foundation for the rational design and application of novel iron supplements.