Rice-Endosperm and Rice-Bran Proteins: A Review

Rice protein is the most preferred protein among all other cereal proteins in terms of its amino acid structure, and it contains the second highest content of lysine, the limiting amino acid in cereals. Processing rough rice into edible rice yields different by-products including rice bran. Rice-endosperm and rice-bran proteins are known to be hypoallergenic, nutritious, and healthful, which gives them high potential in the food-ingredient industry, especially in gluten-free preparations and in infant formulas. Multiple methods can be used for the extraction of rice-endosperm and rice-bran proteins, including chemical and enzymatic extraction methods. The functional properties, including emulsification, foaming, gelation, and water and oil absorption, of rice-endosperm and rice-bran proteins require enhancement before utilizing them in food applications because of their low solubilities, which affects the other functionalities. Enhancement methods include manipulating pH and salt concentration of extracting solvents and selecting specific extraction procedures. Rice-endosperm and rice-bran peptides are known to exhibit different bioactivities. These peptides can be generated by different hydrolysis approaches, including the enzymatic, chemical, or microbial assays. Some of the confirmed bioactivities of rice-endosperm and rice-bran peptides are the antioxidant, antihypertensive, anticancer, anti-inflammatory, and antimicrobial activities. These bioactivities increase the potential of rice-endosperm and rice-bran proteins to be utilized in food applications, as natural preservatives, or in pharmaceutical applications.