Steam cooking drives alterations of proteomics, protein structural and functional properties in rice (Oryza sativa l.)

Rice, as an important staple food consumed by people, is gradually becoming a concern for many consumers in terms of its eating quality. Many studies have found that protein is an important factor to determine the edible quality of rice. However, the protein changes during rice cooking have not been compared and studied in detail. In this study, the structural and functional characteristics of rice proteins before and after steaming were comprehensively compared. Meanwhile, proteomic strategies were also applied to analyze changes in protein composition and expression. Steaming promoted the aggregation of cooked rice proteins, resulting in a more compact structure and a significant increase in particle size (raw rice, 304.33 nm; cooked rice, 565.17 nm). Compared with raw rice protein (43.33%; 133.91%), the solubility (22.29%) and foaming capacity (119.53%) of cooked rice protein were significantly reduced, while emulsion activity was slightly improved. The differential abundance proteins were found to be predominantly down-regulated after steaming (238 proteins) and mostly enriched in metabolic pathways. The steaming process of rice mainly involves oxidative phosphorylation, thiamine metabolism, ether lipid metabolism, glycerophospholipid metabolism, multiple amino acid metabolism and other metabolic pathways, and they are closely related to each other. This study deepens the understanding of proteomic changes and structural/functional properties of rice proteins during steaming.