Manipulating gelatinization, retrogradation, and hydrogel properties of potato starch through calcium chloride-controlled crosslinking and crystallization behavior

Abstract

Due to the inherent susceptibility of single-polymer starch molecules to retrogradation, the practical application of green starch hydrogels is remarkably limited. Here, we propose a simple strategy to achieve the multifunctionality of starch hydrogels by employing polymer amorphization. Calcium chloride was used to promote the gelatinization of starch granules, disrupting their crystalline structure without the need for heating. Additionally, during the initial stage of hydrogel formation, the effects induced by calcium chloride effectively suppressed starch retrogradation. This suppression induced the formation of uniform aggregates of polymer chains, enabling tunable polymer amorphization and the coexistence of free hydroxyl and hydrogen-bonding hydroxyl groups. The multiscale microstructure yielded starch-based hydrogels with favorable water-retention capabilities, high transparency (86.39 %), improved self-adhesive and self-healing properties, excellent stretchability (146 %), tissue-like ultra-softness (Young's modulus <10 kPa), and anti-freezing properties (<−50 °C). Overall, this study systematically elucidates the underlying mechanisms of CaCl₂ impacts on starch gelatinization, retrogradation, and hydrogel properties, paving the way for the on-demand functionality of starch hydrogels through regulated crystallization.