Improvement of the water solubility and emulsifying capacity of rice proteins through the addition of isolated soy protein

Summary The market for rice protein (RP) has been steadily growing, but applications of RPs as food ingredients and functional materials are limited due to poor solubility in water. Here, the complex of RP and isolated soy protein (ISP) was prepared, and the potential utility of RP–ISP complex as an emulsifier was evaluated. The solubility of the RP solution was 25.8% whereas it was greatly increased to 68.4% in the RP–ISP complex. The properties of RP and RP–ISP complex were assessed by scanning electron microscope, gel electrophoresis, circular dichroism, and surface hydrophobicity test. Next soybean oil emulsions were prepared using the RP and RP–ISP complex. The RP‐stabilised emulsion was unstable to storage. In contrast, the RP–ISP complex‐stabilised emulsions showed good stability, especially when more than 0.2% ISP was added. These data suggest that the preparation of soluble RPs by ISP could expand the applications of RP in the food industry.