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

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.