Tunable rice protein–starch composite soft gels: Structural role of ultrasound-modified protein

Soft composite gels were prepared with ultrasound-treated rice protein (URP, 4%) and rice starch (RS, 6%). The compositional and physical attributes of URP were elucidated, and the textural, rheological and structural properties of the composite gels were characterized. URP showed a reduced particle size, improved solubility, and increased heat tolerance. Cooked (65 °C for 20 min, then heated to 95 °C at 1 °C/min) RS + URP gels displayed a homogeneous and smooth texture with a range of reduced hardness (62%–78.3%) compared with RS gel while largely retaining the water-holding capacity. The viscosity and shear moduli (Gʹ and G′′) of the gels decreased correspondingly, and starch retrogradation was partially inhibited by the interaction with URP. A salient amorphous state revealed by X-ray diffraction confirmed weaker amylose association, in corroboration with non-covalent interactions between RS and URP shown by FTIR spectroscopy. These findings suggest that URP can be a functional ingredient for the development of soft, protein-rich, starch-based gel products suitable for the dysphagia diet.