Comparative studies on physicochemical and structural properties of rice proteins

Rice (Oryza sativa L.) is a global staple, increasingly recognized for the nutritional and functional properties of its proteins (P). Protein characteristics change significant during rice grain development, encompassing flowering, milky, dough, and mature stages, each potentially suitable for distinct food applications. This study evaluated the impact of grain maturity on the physicochemical and structural properties of proteins in young (Y) and mature (M) grains from four rice varieties; Jasmine Rice 105 (JRP105), Hom Warin (IRP57514), RD6 (RDP6), and Hom Naka (HNKP); Parameters investigated included protein content, solubility, molecular weight distribution, amino acid composition, and secondary structures.

Young rice proteins, particularly from Y-HNKP and Y-IRP57514 varieties, demonstrated significantly higher protein content (633.3 g kg^-1) and solubility (19.20%) compared to mature grains. Mature rice proteins, especially from M-HNKP, exhibited higher proportion of β-sheet structures (100%) and lower solubility (11.41%), mainly attributed to increased protein aggregation and enhanced hydrophobic interactions. Additionally, young rice grains, notably Y-RDP6, presented a superior profile of essential amino acids, while mature grains displayed a complex molecular weight distribution due to accumulated storage protein.

This study highlights significant differences in protein characteristics between young and mature rice grains. Young rice proteins, notably from Y-JRP105 and Y-IRP57514, are characterized by higher protein content, greater solubility, and enhanced bioavailability, making them ideal for applications in high-protein foods and dietary supplements. Conversely, mature rice proteins, particularly from M-HNKP, exhibit increased structural stability due to higher β-sheet content and protein aggregation, making them suitable for demanding applications and storage stability. © 2025 Society of Chemical Industry.