Nanoemulsion of γ-Oryzanol-Rich Rice Bran Oil Obtained by Ultrasound and Supercritical Fluid Extraction from White and Parboiled Rice Brans

This study aimed to extract rice bran oil rich in γ-oryzanol from white (WB) and parboiled rice bran (PB) using ultrasound as a pre-treatment to supercritical fluid extraction (US + SFE), supercritical fluid extraction (SFE), and conventional solvent extraction. PB oil exhibited superior quality compared to WB, with low free fatty acid (FFA) levels and higher γ-oryzanol content. PB oil extracted by US + SFE achieved a yield of 18.2 ± 0.4%, γ-oryzanol content of 1.53 ± 0.19 g 100 g−1, and low FFA content (0.27 ± 0.01%), showing improved oil quality compared to SFE (yield 13.5 ± 0.3%, γ-oryzanol 1.13 ± 0.08%, FFA 0.55 ± 0.01%) and conventional extraction (yield 25.0 ± 1.3%, γ-oryzanol 2.03 ± 0.04%, FFA 1.12 ± 0.01%). The US + SFE oil also showed lower peroxide value (1.7 mEq kg−1) and preserved fatty acid profiles containing palmitic, oleic, and linoleic acids. US induced structural disruption in bran, enhancing oil release. Additionally, chitosan–gelatin nanoemulsions were developed to protect the extracted oil. Formulations exhibited droplet sizes of 119–352 nm, polydispersity indices below 0.3, and zeta potentials from –12.4 to 38.8 mV. Gelatin-based nanoemulsions maintained FFAs at 0.56 ± 0.2% and peroxide values at 4.71 ± 0.2 mEq kg−1 over 90 days, demonstrating superior oxidative stability. These results highlight the potential of US and SFE combined with nanostructured delivery systems to valorize agro-industrial byproducts and develop stable, functional ingredients and drug carrier systems.