Enhancement of the rice protein solubility using industry-scale microfluidization and pH cycling: A mechanistic study

Rice protein has attracted attention as a functional ingredient in foods and beverages due to its high abundance, low cost, hypoallergenicity, and good nutritional profile , but its large-scale commercial application is currently limited due to its poor solubility. In this study, a combination of industry-scale microfluidizer system and pH (ISMS-pH) cycling to improve the water dispersibility of rice protein was investigated. This process was found to increase the dispersibility of a commercial rice protein ingredient from around 1.4 to 78.3%. Morphological analysis showed that the microfluidization-alkaline treatment reduced the particle size of the rice protein aggregates. In addition, the molecular weight and disulfide bond content of the proteins decreased after processing, while the intrinsic fluorescence intensity and surface hydrophobicity increased. Secondary structure analysis showed that some of the β-sheet structure was converted into α-helix structure by processing. The ISMS-pH cycling process also enhanced the functional attributes of the rice proteins, including their emulsification and foaming properties. In summary, we have shown that rice protein ingredients with high water dispersibility can be produced on an industrial scale and have provided valuable insights into the mechanisms underlying their improved functionality. This research may therefore lead to new approaches for creating functional rice protein ingredients for commercial applications in the food and other industries. • ISMS-pH cycling highly enhanced the solubility (78.3%) of RP. • RP with high solubility can be produced by ISMS-pH cycling on an industrial scale. • ISMS-pH cycling promoted partial protein unfolding and dissociation of aggregates. • ISMS-pH cycling enhanced the functional attributes of the rice proteins.