Optimization of Protocol for High-Quality Γ-Oryzanol Extraction and Spray Drying from Rice Bran

Background: γ-Oryzanol is present in rice bran, offering antioxidant and antiinflammatory properties and helping reduce blood cholesterol levels. Objective: This study aimed to optimize the extraction and enrichment of γ-oryzanol from rice bran, produce γ-oryzanol powder, and test its antioxidant and anti-diabetic activities, which serve as quality indicators of the powder. Methods: γ-Oryzanol rich fraction (ORF) was extracted from Hom Mali rice bran using different extraction methods and three dewaxed-degummed protocols. Then, γ-oryzanol powder was produced using a spray dryer at different inlet temperatures of 150, 170, 190, and 210 °C. Results: Maceration with ethanol and protocol 1 of dewax-degum had the highest γ-oryzanol content, 1.83 mg/g of rice bran. The highest γ-oryzanol contents were observed at 150 °C and 170 °C, with no significant difference. Furthermore, powder produced at 150 °C exhibited the best antioxidant activities, with the lowest IC50 of ABTS (812.75 μg/mL) and the highest ferricreducing antioxidant power (9.16 μg TE/mg). In terms of anti-diabetic activity, γ-oryzanol powders at all inlet temperatures demonstrated good α-glucosidase inhibitory activity (IC50 = 1.13- 1.56 mg/mL) and α-amylase inhibitory effect (IC50 = 130.50-145.86 μg/mL). Conclusion: Therefore, maceration with ethanol for 7 days and protocol 1 of dewaxeddegummed, which uses acetone, methanol, and freezing, is the best method to obtain high γ- oryzanol content. Additionally, the spray dryer operating at 150 °C can produce high-quality γ- oryzanol powders with elevated levels of γ-oryzanol, antioxidant activity, and anti-diabetic properties.