Structural Characterization of Sodium Alginate-Albumen Gel Beads for Loading of Fe(Ⅲ): 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 Fe(Ⅲ) 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 Fe(Ⅲ) loading. The adsorption of Fe(Ⅲ) was more in line with the pseudo-second-order kinetic model, indicating that chemisorption could be considered as the dominant mechanisms of Fe(Ⅲ) adsorption. In the first adsorption stage of the intraparticle diffusion model, the rapid diffusion of Fe(Ⅲ) 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 Fe(Ⅲ) 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 Fe(Ⅲ) 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.