Formation of nanoporous aerogels from defatted rice bran via supercritical carbon dioxide drying

Abstract

Rice bran (∼8–10% of the total rice weight), generated in large quantities during rice processing, is an underutilized rice processing byproduct. The objective of this study was to upcycle defatted rice bran into starch and protein-based nanoporous aerogels using supercritical carbon dioxide (SC-CO₂) drying. Specifically, crude starch-1, crude starch-2, and protein aerogels were prepared at three different concentrations of 10, 15, and 20% (w/w). The generated aerogels were characterized for their morphology, crystallinity, chemical interactions, textural properties, solubility, and thermal stability. The aerogels (15%, w/w) prepared from rice bran crude starch and protein formed a three-dimensional interconnected open porous structure. At this concentration, protein aerogels revealed the highest surface area of 25.3 m² g⁻¹, a pore size of 22 nm, and a pore volume of 0.13 cm³ g⁻¹, whereas crude starch-1 and crude starch-2 aerogels had surface areas of 19.7 and 21.3 m² g⁻¹, pore sizes of 22 and 18 nm, and pore volumes of 0.10 and 0.09 cm³ g⁻¹, respectively. All the aerogels exhibited densities lower than 0.3 g cm⁻³ with porosities higher than 82%. Overall, this study generated high-value starch and protein-based aerogels that can be used for developing functional foods to deliver bioactive compounds, thereby adding value to the underutilized defatted rice bran.