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

## TL;DR

Ultra-high pressure processing improves rice starch properties for use in semi-solid and low-digestibility foods.

## Contribution

This study pioneers the use of ultra-high pressure processing for rice starch-calcium gluconate complexes.

## Key findings

- UHP at 500 MPa produces complexes with low viscosity and high gel fluidity.
- UHP at 200 MPa increases resistant starch content to 36%, surpassing conventional methods.

## Abstract

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.

•Pioneering use of ultra-high pressure (UHP) for starch-calcium gluconate complexes.•Calcium gluconate boost solubility, gel fluidity, and resistant starch (RS) content.•500 MPa UHP yields lowest viscosity, best fluidity; 200 MPa maximizes RS (36 %).•UHP-prepared Ca2+-starch enables semi-solid & low-digestibility foods applications.

Pioneering use of ultra-high pressure (UHP) for starch-calcium gluconate complexes.

Calcium gluconate boost solubility, gel fluidity, and resistant starch (RS) content.

500 MPa UHP yields lowest viscosity, best fluidity; 200 MPa maximizes RS (36 %).

UHP-prepared Ca2+-starch enables semi-solid & low-digestibility foods applications.