From micropores to mechanical strength: Fabrication and characterization of edible corn starch-sodium alginate double network hydrogels with Ca2+ cross-linking

Abstract

This study explores the fabrication and characterization of corn starch‑sodium alginate double network hydrogels using two distinct calcium ion cross-linking methods: the gluconolactone immersed method (GIM) and the calcium chloride immersed method (CCIM). We investigated the ionic cross-linking mechanism of these hydrogels and compared their microstructure and mechanical properties. Our results highlight significant differences between GIM and CCIM hydrogels, with the CCIM method producing a more uniform and compact network. At the same calcium ion concentration, CCIM hydrogel exhibited higher mechanical strength and viscoelasticity properties compared to GIM hydrogel. The rapid release of Ca2+ in CCIM allowed for complete cross-linking with sodium alginate, forming a uniform 3D network structure. In contrast, the slow released Ca2+ in GIM resulted in a heterogeneous structure with a tough outer shell and incomplete internal cross-linking. Specifically, the CCIM hydrogel showed a compact network structure and the highest mechanical strength at a calcium chloride concentration of 1.6% (w/v). This study demonstrates that the Ca2+ release rate significantly impacts the microstructure and mechanical properties of double network hydrogels prepared by the immersion method. With this preparation strategy, corn starch‑sodium alginate edible gels that provided higher strength could be fabricated.