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Extracting Phenolic Compounds from Rice Husk with Supercritical CO2

Extracting Phenolic Compounds from Rice Husk with Supercritical CO2

In much of the world, rice is a primary food source. Every year, large amounts of rice husk are left over from rice processing, requiring disposal. While generally considered worthless, rice husk contains significant amounts of phenolic compounds. These compounds are of interest because their antioxidant properties have been shown to reduce the incidence of certain chronic diseases, such as cardiovascular disease, cancer and neurodegenerative conditions (1).

Ali Ubeyitogullari and Sumanjot Kaur at The University of Arkansas, used an SFT-120 SFE to determine the optimal parameters for obtaining high yields of various phenolic compounds from rice husk (2). The husk was ground up and packed into a 100ml vessel. Key extraction parameters they investigated were processing temperatures of (40-60oC), pressures of (30-40 MPa) and co-solvent ratios of (15-25% w/w ethanol). The co-solvent was required because neat SC-CO2 is not able to solubilize and extract the moderately polar phenolic acids. After the initial process optimization was achieved, they explored replacing some of the ethanol with water to achieve the best results.

Total phenolic content (TPC) was determined and compared to results obtained with the traditional methanol extraction method. The results were comparable, but the SC-CO2 method eliminated the need for toxic solvents which are unsuitable for use in food applications. Ubeyitogullari believes the process has the potential to be scaled up to industrial scale uses.
The SFT-120 is a moderately priced laboratory SFE, covering the full range of temperatures and pressures required by the majority of supercritical extraction applications. To learn more about this versatile SC-CO2 extractor, please see: SFT-120 – Supercritical Fluid Technologies (


(1) Phenolic compounds in fruits and beverages consumed as part of the mediterranean diet: their role in prevention of chronic diseases, Yolanda Aguilera,, Phytochemistry Reviews, October, 2015.

(2) A. Ubeyitogullari and S. Kaur, Dept. of Food Science, University of Arkansas, Fayettsville, AR.