Ultra-high pressure processing enhances structural, rheological and in vitro digestibility properties of rice...

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 in vitro 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.