Potentially texture-modified food for dysphagia: Gelling, rheological, and water fixation properties of rice starch–soybean protein composite gels in various ratios

Starch and protein are essential biomacromolecules ubiquitous in foods that contribute to nutritional and textural properties. Understanding the gelling behavior of starch and proteins can help develop texture-modified foods. Herein, composite gels were created with various ratios of rice starch to soybean protein (constant solid content 12%). The International dysphagia diet standardization initiative (IDDSI) levels of rice starch–soybean protein composite gels with various ratios were evaluated. The texture, gelling behavior, rheological properties, and water fixation properties of rice starch–soybean protein gel were characterized. The results showed that soybean protein inhibit the gelatinization of rice starch by reducing the gelatinization viscosity. Rice starch could prevent the denaturation of soybean protein by preventing the structural transformation of protein. Rice starch and soybean protein antagonize each other to inhibit gelation. In addition, rice starch precedes soybean protein gel so that the network formation of rice starch and soybean protein is hindered by each other in the composite system. Obvious phase separation was observed in the rice starch–soybean protein composite gel. Disulfide and hydrogen bonds are affected by the proportions of rice starch and soybean protein and are the main intermolecular forces to maintain structure. Gels prepared with a mixture of rice starch and soybean protein had lower IDDSI levels, gel strength, modulus, and strain compared to single-component gels. All gels exhibit excellent water-holding capacity. Therefore, the rice starch–soybean protein composite gel can be used to prepare soft and moist texture-modified foods to meet the needs of patients with dysphagia.