Date of Graduation


Document Type


Degree Name

Master of Science in Food Science (MS)

Degree Level



Food Science


Ali Ubeyitogullari

Committee Member

Ya-Jane Wang

Second Committee Member

Jin-Woo Kim


Rice husk and bran, byproducts of rice processing, are generated in large quantities (~30-40% of the total rice weight) and are discarded as waste or burned in an open field, creating a major disposal problem for the rice industry. However, these byproducts contain high-value compounds, including phytochemicals, fiber, and proteins. Therefore, the goal of this study was to generate high-value food ingredients from rice processing byproducts using a green, innovative approach based on supercritical carbon dioxide (SC-CO2) technology. Specific objectives were to (i) extract health-promoting phytochemicals from rice husk and (ii) convert rice bran into nanoporous materials using SC-CO2. First, SC-CO2 conditions, specifically temperature (40 and 60 ℃), pressure (30 and 40 MPa), and ethanol concentration (15 and 25%), were optimized for the highest total phenolic yield. In addition, the effect of cosolvent type (i.e., ethanol and ethanol-water) was investigated. The extracts were characterized for their total phenolic and flavonoid contents (TPC and TFC, respectively), and antioxidant activities (AA). The highest total phenolic yield was achieved at 30 MPa and 60 ℃ with a 25% ethanol-water mixture as a cosolvent. Further, the defatted rice bran was utilized for generating nanoporous starch and protein aerogels via SC-CO2 drying. The generated aerogels were characterized for their morphology, crystallinity, chemical structure, textural properties, solubility, and digestibility. The concentration was optimized based on the gel stability of hydrogels, and 15% concentration revealed the best gel structure with open pores. The crude starch aerogels showed the highest surface area (46 m2/g) and pore volume (0.13 cm3/g). The aerogels revealed densities lower than 0.3 g/cm3 and porosity of higher than 82%. The textural properties were improved using a high-shear mixer compared to magnetic stirrer. The generated starch and protein aerogels were subjected to simulated digestion to investigate their hydrolysis. The protein hydrolysis was higher in protein aerogels (84%). Overall, this research creates new health-promoting food ingredients while increasing the sustainability of rice production.

Available for download on Saturday, August 30, 2025

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