Composition of Rice Bran Stearin from Various Refineries Across China

Effects of Extraction Processes on the Oxidative Stability, Bioactive Phytochemicals, and Antioxidant Activity of Crude Rice Bran Oil

This research investigates the effects of different extraction processes on the oil extractability, oxidative stability, bioactive compounds, and antioxidant activity of crude rice bran oil (CRBO). The experimental extraction processes include hexane extraction (HE), cold press extraction (CE), thermally pretreated cold press extraction (CCE), and ultrasound-pretreated cold press extraction (UCE). The results show that thermal cooking and ultrasound pretreatment significantly improve the oil extractability of the cold press extraction process. The oil yields of CE, CCE, and UCE were 14.27, 17.31, and 16.68 g oil/100 g rice bran, respectively. The oxidative stability of CE and CCE oils was higher than HE and UCE oils, as evidenced by the synchrotron-radiation-based Fourier transform infrared (SR-FTIR) absorption peak. The ρ-anisidine values of HE, CE, CCE, and UCE were 0.30, 0.20, 0.91, and 0.31, respectively. Meanwhile, ultrasound pretreatment significantly reduced the bioactive compounds and chemical antioxidant activity of UCE oil. The CE, CCE, and UCE oils (0.1% oil concentration) exhibited higher inhibitory effects against hydrogen-peroxide-induced cellular oxidative stress, compared to HE oil (0.39% oil concentration). Essentially, CCE is operationally and environmentally suitable for improving the oil yield, oxidative stability, bioactive compounds, and antioxidant activities of CRBO.

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

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°C); 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% Na₂CO₃ 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.

Iron Encapsulation in Water-in-Oil Emulsions: Effect of Ferrous Sulfate Concentration and Fat Crystal Formation on Oxidative Stability

Iron deficiency is a major global human health concern. Encapsulation of iron in functional food products may help to solve this problem. However, iron is highly reactive and may promote rapid lipid oxidation in fatty foods. In this study, the effect of ferrous sulfate (0.1 to 0.5 wt%) and rice bran stearin (0 or 30 wt%) on the physical properties, oxidative stability, and encapsulation efficiency of 20 wt% water-in-oil (W/O) emulsions stabilized with polyglycerol polyricinoleate was investigated. In the presence of rice bran stearin crystals in the continuous oil phase, W/O emulsions had smaller mean droplet diameters (d ∼ 250 nm) and better physical stability than its absence (d ∼ 330 nm). An increase in the ferrous sulfate concentration in the water droplets led to a decrease in the oxidative stability of the W/O emulsions. However, the presence of rice bran stearin significantly (P ≤ 0.05) improved their oxidative stability. Moreover, addition of rice bran stearin also significantly (P ≤ 0.05) improved the encapsulation efficiency and delayed ferrous sulfate release from the W/O emulsions. The impact of pH and ionic strength on the encapsulation efficiency of the W/O emulsion was also investigated. Ionic strength affected the encapsulation efficiency much more than pH. The W/O emulsions created in the present study may be useful for the encapsulation and delivery of iron and other water-soluble nutrients into food products.

PRACTICAL APPLICATION

Water-in-oil (W/O) emulsions may be used to encapsulate, protect, and deliver water-soluble bioactive compounds or nutrients into food products. In this study, W/O emulsions stabilized using an oil-soluble surfactant (polyglycerol polyricinoleate, PGPR) and fat crystal network (rice bran stearin) were shown to be useful for encapsulation and delivery of iron into foods. This strategy may be a promising approach to reduce iron deficiency, a major nutritional deficiency for people with inadequate food supplies.