Abstract
Rice husk (RH), an underutilized by-product of rice milling, represents a promising source of dietary fiber with health-promoting potential. This study investigated the effects of growth stage and particle size on the chemical composition and functional properties of dietary fiber isolated from green rice husk (G-RH) and ripe rice husk (R-RH). Cellulose contents ranged from 62 to 85 g/100 g DW in G-RH and from 38 to 73 g/100 g DW in R-RH, while β-glucan levels were 66-85 mg/g DW and 67-92 mg/g DW, respectively. FTIR and XRD analyses confirmed the presence of cellulose and its crystalline structure. Particle size reduction enhanced water- and oil-holding capacities (up to five-fold and two-fold, respectively) and increased phenolic, flavonoid, and phytosterol contents. G-RH exhibited higher levels of bioactive compounds and a more diverse phytosterol profile compared to R-RH, as verified by GC-MS analysis. In contrast, R-RH showed greater water-holding capacity, whereas G-RH displayed superior oil-holding capacity, underscoring the influence of growth stage on dietary fiber functionality. Overall, these findings highlight rice husk, particularly G-RH, as a promising functional ingredient for food applications.