Effect of High Hydrostatic Pressure on the Physicochemical and Rheological Properties of Corn Starch: Dual Physical Modification to Obtain a Natural Hydrogel

The effect of high hydrostatic pressure (HHP) treatment on the physicochemical and rheological properties of starches with different structural organizations (granular or retrograded) was evaluated. Granular starch (NS) and retrograded starch (RetS) were adjusted to a moisture content of 40% (w/v) and subjected to pressurization at 300 and 600 MPa for 5 min at 10 °C. In NS, HHP treatment reduced the resistant starch (RS) content and consistency index (K). However, the swelling power (SP) and water solubility (WS), measured at 25 and 90 °C, increased, which allowed for the formation of well-structured gels, as indicated by the increase in storage modulus (G′) and loss modulus (G″). In RetS, the dual physical modification (retrogradation + HHP) increased the RS and K values, and the hydration ability was improved, as indicated by enhanced SP at 25 and 90 °C. However, the release of the linear molecular components was restricted, resulting in lower WS values, hindering the interactions between the polymeric chains conforming the gel, and decreasing G′ and G″. Analysis of RetS demonstrated that the dual physical modification process resulted in starch with properties suitable for use as a natural hydrogel for encapsulation, protection, or controlled release applications of active ingredients in industries that require thermal processing for its preparation. This approach preserves RetS in a dry state, facilitating transportation and extended storage until subsequent rehydration. Overall, the results demonstrate that HHP induces different modifications in physicochemical and rheological properties depending on the structural organization of starch, allowing for the design of natural hydrogels with RetS and gelling material with NS.