Recovery of γ-Oryzanol from Rice Bran Acid Oil by an Acid-base Extraction Method with the Assistance of Response Surface Methodology

Abstract

an inexpensive byproduct, especially using a simple, rapid and low cost process. Crude rice bran oil CRBO contains approximately 1.5-2.9 of γ-oryzanol. However, more than 90 of the initial amount of γ-oryzanol is lost and removed with the rice bran oil soapstock RBOS during the alkali refining process 8. Thus, in industrial practice, the RBOS and its acidulated form known as rice bran acid oil RBAO are excellent sources for recovery of γ-oryzanol. Several processes have been proposed for recovery of the γ-oryzanol from CRBO, RBOS and RBAO 8 14. These processes can be divided into two major consecutive pro-Abstract: A rapid and low energy consumption method for the recovery of γ-oryzanol from rice bran acid oil (RBAO), a byproduct of rice bran oil (RBO) refining, is presented. The RBAO was converted to the fatty acid ethyl ester (FAEE) and was used as the starting material. The dissolved γ-oryzanol was separated from the FAEE using an acid-base extraction method with alkaline aqueous ethanol and hexane as extraction media. A systematic investigation of the extraction yield was carried out by applying response surface methodology (RSM) based on central composite design (CCD) and Derringer's desirability function. The concentration of NaOH, the percentage of ethanol in water, the hexane content and their interactions showed significant effects on the yield of γ-oryzanol and FAEE. The optimal extraction conditions were as follows: extraction time of 1 min at room temperature (28-32℃); extraction medium: 1.855 M NaOH; 75.91% ethanol in water and 20.59% hexane in the total volume of the extractant; and FAEE to extractant ratio of 1:10 corresponding to a maximum γ-oryzanol yield of 75.82±3.44% and the desired FAEE yield of 54.42±7.80%. The γ-oryzanol-rich fraction was further purified by washing with a 2% Na 2 CO 3 solution, obtaining 69.94% recovery yield with 89.90% purity of γ-oryzanol. The purified γ-oryzanol showed good scavenging activity on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and the ABTS radical and was comparable to the commercial product, clearly suggesting that the presented process was efficient and feasible.

Enzymatic esterification/transesterification of rice bran acid oil for subsequent γ-oryzanol recovery

“…The results are comparable to ours, but the resulting reaction product in their study was soap and FFAs rather than biodiesel. In another study by Sombutsuwan et al (2018), acid-catalyzed reactions were used for biodiesel production before the acid-base extraction of γ-oryzanol. The authors reported 76% recovery of γ-oryzanol (based on the amount present in the reaction product) after extraction of the aqueous phase with ethyl acetate, followed by drying under N2.…”

“…γ-oryzanol residing in the resulting reaction product was recovered using an acid-base extraction method, modified from Sombutsuwan et al (2018), in which NaOH was used to transform γ-oryzanol to its anionic phenoxide form (deprotonated) to make it separable from the biodiesel phase. Here, the effect of NaOH concentration on γ-oryzanol recovery was investigated to find the most suitable extraction condition as follows: the biodiesel phase (1 g) was first placed in a 50 mL Erlenmeyer flask on a magnetic stirrer and then mixed with hexane (1 mL), followed by addition of aqueous ethanolic NaOH (4 mL) which was composed of 24.09 %v/v ethanol and 75.91 %v/v of NaOH solution at a specified concentration (1, 2, 3, or 4 M).…”

“…Nevertheless, the separation of γ-oryzanol from the resulting biodiesel was not demonstrated. Sombutsuwan et al (2018) applied acid-catalyzed esterification/transesterification with RBAO, followed by acid-base extraction of γ-oryzanol, in which γ-oryzanol was deprotonated by an alcoholic solution of the strong base to become anionic and in turn phaseseparated from the resulting biodiesel (Hakala et al, 2002). γ-oryzanol extraction yields of up to 76% were reported, although this study did not explore the effects of the reaction conditions on γ-oryzanol recovery.…”

Effect of Mobile Phase Composition on the Separation of Neutral Lipids, γ-Oryzanol and its Saponified Compounds on a 100-Å Phenogel Column

“…In addition, resolutions of solute compounds and the separation power of a single 100-Å Phenogel column were substantially improved when nonpolar solvent, isooctane were incorporated into the common mobile phase, toluene, and/ or tetrahydrofuran with additional a small amount of acetic acid. These were demonstrated for the separations of TG, DG, MG, FFA and wax ester in rice bran wax (Aryusuk et al, 2011), acyglycerols, FFA and OZ in rice bran acid oil (Sombutsuwan et al, 2018) and fatty acid methyl ester and steryl glucoside in biodiesel (Cheewaphan et al, 2019).…”

“…Preparation of rice bioactive compounds such as γ-oryzanol (OZ), ferulic acids (FA), free phytosterols and triterpene alcohols (FS) received much attention due to their various applications in foods, medical and cosmetics (Verma & Srivastav, 2020). Over the last few years, many studies have focused on methods for preparation of these compounds from lowcost by-products of rice bran oil (RBO) refining (Truong et al, 2017, Sombutsuwan et al, 2018. Generally, different of these compounds required different approaches for determination.…”