Ultra-high pressure processing enhances structural, rheological and in vitro digestibility properties of rice starch‑calcium gluconate complexes

Calcium gluconate (CG) is widely used as both a nutrient fortifier and starch modifier. This study pioneers the application of ultra-high pressure (UHP) processing for the preparation of rice starch-CG complexes, in comparison to conventional hydrothermal (H) treatment. The structural characteristics, rheological properties and <i>in vitro</i> digestibility of the complexes were systematically investigated. UHP at 500 MPa yielded complexes with markedly lower pasting viscosity but superior gel fluidity and syneresis stability, ideal for smooth semi-solid foods requiring controlled water release. Meanwhile, UHP at 200 MPa increased resistant starch (RS) content to 36.00 %, significantly surpassing H results and highlighting its potential in low-digestibility functional foods. Although both methods improved solubility and reduced viscoelasticity, UHP enabled precise, pressure-dependent modulation of starch functionality, which is not attainable through conventional heating. These findings demonstrate UHP's potential for tailoring starch functionality, offering new strategies for developing semi-solid foods and low-digestibility foods through precise pressure selection.