Extraction of rice bran oil using aqueous media

Aqueous extraction of oil from rice bran was studied on a laboratory scale and the resulting product was examined. The following process parameters influencing oil extraction were individually investigated: pH of aqueous media, extraction temperature, extraction time, agitation speed and rice bran‐to‐water ratio. Extraction temperature and pH were found to be the main factors influencing oil extraction. The highest oil yield was obtained at pH 12.0, extraction temperature 50 °C, extraction time 30 min, agitation speed 1000 rpm, and rice bran‐to‐water ratio 1.5‐to‐10. The quality of aqueous‐extracted oil in terms of free fatty acid, iodine value and saponification value was similar to a commercial sample of rice bran oil and hexane‐extracted oil, but the peroxide value was higher. Furthermore, the colour of aqueous‐extracted oil was paler than solvent‐extracted oil. © 2000 Society of Chemical Industry     

Ambient-temperature extraction of rice bran oil with hexane and isopropanol

Hexane and isopropanol were compared as solvents for use in ambient-temperature equilibrium extraction of rice bran oil (RBO). Isopropanol was as effective as hexane in extracting RBO when 20 mL of solvent was used to extract 2 g of bran. Free fatty acid levels were 2–3% in both solvents and similar to that previously reported for hexane extraction of RBO hexane extraction by this method. Larger-scale extractions with 30 g of bran and 150 mL of solvent produced oil with a similar free fatty acid content and a phosphorus level of approximately 500 ppm. The oil extracted with isopropanol was significantly more stable to heat-induced oxidation than hexane-extracted oil. Antioxidants that are more easily extracted by isopropanol than hexane may be responsible for the increased stability.     

Comparison of isopropanol and hexane for extraction of vitamin E and oryzanols from stabilized rice bran

The effects of solvent-to-bran ratio (2∶1 and 3∶1, w/w), extraction temperature (40 and 60°C), and time (5, 10, 15, 20, and 30 min) were studied for hexane and isopropanol extraction. Increasing the solvent-to-bran ratios and extraction temperature increased the amounts of crude oil, vitamin E and oryzanol recovered for both solvents. An extraction time of 15 min was sufficient for optimum crude oil, vitamin E, and oryzanol extraction. Preheated isopropanol (3∶1 solvent/bran ratio and 60°C) extracted less crude oil (P<.05) but more vitamin E (P<.05) and similar amounts of oryzanol (P>.05) relative to preheated hexane. The data suggest that isopropanol is a promising alternative solvent to hexane for extraction of oil from stabilized rice bran.     

First approach on rice bran oil extraction using limonene

Edible oil extraction with petroleum derivatives as solvents has caused safety, health, and environmental concerns everywhere. Thus, finding a safe alternative solvent will have a strong and positive impact on environments and general health of the world population, considering the scale of oil extraction operations worldwide. The extraction of oil from rice bran by d‐limonene and hexane (for comparison) has been carried out at their respective boiling points at various solvent‐to‐meal ratios and for various extraction times. The preliminary data suggested that the optimum solvent‐to‐meal ratio and extraction time required for d‐limonene extraction of rice bran oil to be 5:1 and 1 h respectively. The initial quality characteristics (free fatty acid content, oil color, phospholipid content) of crude oil extracted under these optimum conditions were analyzed using various analytical methods based on the standard methods of AOCS and were found to be comparable to the oil extracted with hexane. The initial positive result has paved the way for further studies on issues related to meal qualities as well as to a scale‐up of the method in the near future.     

A Simplified Method for Fractionation and Analysis of Waxes and Oils from Sorghum (Sorghum bicolor (L.) Moench) Bran

In the United States, sorghum is primarily used for animal feed and ethanol production but has potential to provide value-added coproducts including waxes and oil. The surface of sorghum contains 0.1–0.4% wax; however, wax extraction from whole kernels before fermentation may not be economical. An alternative method for this extraction could be facilitated through decortication, abrasion of the surface to remove bran. Decortication increases the starch content of decorticated sorghum, potentially improving ethanol yields, while concentrating wax and oil to the bran. Typically, oil (triacylglycerols) and waxes are extracted from bran in one extraction and waxes are precipitated from oil using cold temperatures then filtration. This research compared traditional fractionation (simulated with a two-step, single-temperature extraction) to a two-step, dual-temperature extraction, whereby oil is first extracted at room temperature and then waxes at elevated temperature. Extractions were performed using an accelerated solvent extractor with hexane or ethanol as solvents. Ethanol extraction showed greater yields (~15% w/w) compared to those of hexane (~11% w/w) because polar materials were extracted. Using hexane, the two-step, dual-temperature fractionation separated waxes from oils via the temperature of extraction solvent with similar purity to the traditional method that fractionated via cold precipitation and filtration. For ethanol, the traditional single-step method fractionated with higher wax purity but lower oil purity compared to the two-step, dual-temperature fractionation.     

Rapid equilibrium extraction of rice bran oil at ambient temperature

Rapid equilibrium extraction of soybean flour has been effective in obtaining an oil with reduced phospholipid content. This technique was examined to obtain a low phospholipid and low free fatty acid rice bran oil (RBO). The amount of RBO extracted with hexane from 1 g of rice bran at 22°C was measured over a 10-min period. The amount of oil extracted from variable amounts of bran with a fixed volume of solvent was also studied. Ninety percent of the oil was extracted in one minute, with 93% of the total RBO being extracted after ten minutes. This compares with the 98% yield obtained from soy flour, but increasing the amount of bran used did not reduce the extraction rate. This extraction method produced a good quality RBO with low phospholipid, low free fatty acid and low peroxide values.     

Effect of method of stabilization on aqueous extraction of rice bran oil

Rice bran oil is widely used in pharmaceutical, food and chemical industries due to its unique properties and high medicinal value. In this study aqueous extraction of rice bran oil from rice bran available in Sri Lanka, was studied. Key factors controlling the extraction and optimal operating conditions were identified. Several methods of bran stabilization were tested and the results were analyzed. The yield and quality of aqueous extracted oil was compared with hexane extracted oil.Aqueous extraction experiments were conducted in laboratory scale mixer–settler unit. Steaming, hot air drying, chemical stabilization and refrigeration better controls the lipase activity compared to solar drying. Steaming is the most effective stabilization technique. The extraction capacity was highest at solution pH range 10–12. Higher oil yield was observed at higher operating temperatures (60–80 °C). Kinetic studies revealed that extraction was fast with 95% or more of the extraction occurring within first 10–15 min of contact time. Parboiling of paddy increases the oil yield. Highest oil yield of 161 and 131 mg/g were observed for aqueous extraction of parboiled bran and raw rice bran respectively. The aqueous extracted oil was low in free fatty acid content and color compared to hexane extracted rice bran oil and other commonly used oils. Major lipid species in rice bran oil were oleic, linoleic and palmitic.     

Effects of the extraction conditions on the yield and composition of rice bran oil extracted with ethanol—A response surface approach

Rice bran oil was obtained from rice bran by solvent extraction using ethanol. The influence of process variables, solvent hydration (0-24% of water, on mass basis), temperature (60-90 °C), solvent-to-rice bran mass ratio (2.5:1 to 4.5:1) and stirrer speed (100-250 rpm) were analysed using the response surface methodology.The extraction yield was highly affected by the solvent water content, and it varied from 8.56 to 20.05 g of oil/100 g of fresh rice bran (or 42.7-99.9% of the total oil available) depending on the experimental conditions. It was observed that oryzanol and tocols behave in different ways during the extraction process. A larger amount of tocols is extracted from the solid matrix in relation to γ-oryzanol. It was possible to obtain values from 123 to 271 mg of tocols/kg of fresh rice bran and 1527 to 4164 mg of oryzanol/kg of fresh rice bran, indicating that it is feasible to obtain enriched oil when this renewable solvent is used. No differences in the chemical composition of the extracted oils were observed when compared to the data cited in the literature.     

米糠精制产品的应用

对米糠综合利用的途径进行了详细论述；并总结厂各种米糠精制产品在日用化工、医药工业、食品工业、精细化工领域的具体用途，包括米糠油的浸提技术，米糠油作为营养保健食品的开发利用，米糠油作为油脂化工原材料的深加工；米糠油精炼皂脚中提取游离脂肪酸及脂肪酸衍生物的制备；米糠脱水、脱臭、脱色的小皂化物提取谷甾醇、生育酚、谷维素的方法；米糠脱蜡副产物制备糠蜡和二十烷醇的利用及米糠饼(粕)提取植酸钙、植酸和肌醇的利用途径，最后提出了大力发展我国米糠产业的市场前景。     

Enzymatic process for extracting oil and protein from rice bran

Enzymatic extraction of oil and protein from rice bran, using a commercial protease (Alcalase), was investigated and evaluated by response surface methodology. The effect of enzyme concentration was most significant on oil and protein extraction yields, whereas incubation time and temperature had no significant effect. The maximal extraction yields of oil and protein were 79 and 68%, respectively. Further, the quality of oil recovered from the process in terms of free fatty acid, iodine value, and saponification value was comparable with solvent-extracted oil and commercial rice bran oil, but the peroxide value was higher.     

Experimental data and modeling of rice bran oil extraction kinetics using ethanol as solvent

The extraction kinetics of rice bran oil (RBO), free fatty acids (FFA), and oryzanol using ethanol (0 and 6.3 mass % of water) at 40°C–70°C were investigated. High extraction temperatures increased the yields of RBO and oryzanol by increasing the diffusivity of the solvent, regardless of its water content. Two models that permitted the estimation of mass transfer and diffusion coefficients were fitted to the oil extraction data with low average relative deviations (≤5.92%). The diffusion coefficient (1.93–7.46 × 10^–10 m²?s^–1) increased with increasing temperature and decreasing hydration of the solvent.     

Recovery of Oil,Erucic Acid,and Phenolic Compounds from Rapeseed and Rocket Seeds

Erucic acid‐enriched oil, sought for industrial purposes, from rapeseed (agronomic plant) and rocket seeds (non‐agronomic plant) was extracted by three different processes: supercritical CO₂, mechanical expression, and hexane extraction. Oil extraction yields were determined and the extracted oils were characterized for their fatty acid and phenolic compound compositions. Higher oil yields were achieved using hexane compared to mechanical expression and supercritical CO₂ extractions. Fatty acid analysis indicated a higher content of erucic acid in rapeseed oil than in rocket oil. In addition, supercritical CO₂ extraction allowed better recovery of phenolic compounds with high antioxidant activities. The most prominent identified polyphenols were vanillin, sinapic acid, syringic acid, and apigenin.     

Rice brain oil. I. Oil obtained by solvent extraction

1. Freshly milled rice bran has been extracted with commercial hexane and the recovered oil and extracted meal examined for their respective content of wax. The oils were refined and bleached by standards as well as several special methods. The crude, caustic soda refined, and several refined and bleached oils were examined spectrophotometrically.
2. When freshly milled rice bran of good quality is extracted with commercial hexane, an oil of relatively low free fatty acid content is obtained. This oil possesses good color and is as stable as other similar types of crude oils.
3. If the oils is extracted from the brain at a temperature below about 10°C. and the extraction is discontinued at the right time, the extracted oil represents 90–95% of the total lipids in the brain and contains very little wax. This wax, which is readily extracted with hot commercial hexane as well as other types of solvents, amounts to about 3–9% of the total extractable lipids.
4. When subjected to ordinary caustic soda refining methods, good rice brain oils behave much like cottonseed oils of comparable free fatty acid content. Both caustic soda refining in a hydrocarbon solvent and refining with sodium carbonate result in refining losses approximating the absolute or Wesson loss.
5. Some of the refined oils when bleached according to usual practice produce products acceptable for use in the edible trade. However, refined rice bran oil has a definitely greenish cast resulting from the presence of chlorophyll, but this color can be removed by bleaching with a small amount of activated acidic clay.

     

Supercritical carbon dioxide extraction of fatty and waxy material from rice bran

Waxy and fatty materials were removed from rice bran by supercritical carbon dioxide at pressures up to 28 MPa and temperatures between 40 and 70°C. The yields of the supercritical extraction were only 16–60% of those obtained by Soxhlet extraction with hexane. The highest yield was reached at the highest pressure and temperature used (28 MPa and 70°C), indicating that supercritical extraction of this lipid-bearing material could probably be improved at more severe extraction conditions. The supercritical extract obtained at operational conditions giving high yield was chromatographically characterized. Compared to the hexane extract, the supercritical extract was lighter in color and richer in wax content and long-chain fatty acids C₂₀−C₃₄. Triacontanol was the most abundant alcohol in both extracts. Tocopherol contents were similar.     

用固定化脂肪酶Candida sp．99-125由粗米糠油酶法合成脂肪酸甲酯

The non-edible crude rice bran oil was extracted from white rice bran, and then was catalyzed by immobilized lipase for biodiesel production in this study. The effects of water content, oil/methanol molar ratio, temperature, enzyme amount, solvent,number of methanol added times and two-step methanolysis by using Candida sp. 99-125 as catalyst were investigated. The optimal conditions for processing 1 g rice bran oil were: 0.2 g immobilized lipase, 2 ml n-hexane as solvent, 20% water based on the rice bran oil mass, temperature of 40 °C and two-step addition of methanol. As a result, the fatty acid methyl esters yield was 87.4%. The immobilized lipase was proved to be stable when it was used repeatedly for 7 cycles.     

Extraction of rice brain oil using supercritical carbon dioxide and propane

Extraction of rice bran lipids was performed using supercritical carbon dioxide (SC−CO₂) and liquid propane. To provide a basis for extraction efficiency, accelerated solvent extraction with hexane was performed at 100°C and 10.34 MPa. Extraction pressure was varied for propane and SC−CO₂ extractions. Also, the role of temperature in SC−CO₂ extraction efficiency was investigated at 45,65, and 85°C. For the SC−CO₂ experiments, extraction efficiencies were proportional to pressure and inversely proportional to temperature, and the maximal yield of oil achieved using SC−CO₂ was 0.222±0.013 kg of oil extracted per kg of rice bran for conditions of 45°C and 35 MPa. The maximal yield achieved with propane was 0.224±0.016 kg of oil per kg of rice bran at 0.76 MPa and ambient temperature. The maximum extraction efficiencies of both SC−CO₂ and propane were found to be significantly different from the hexane extraction baseline yield, which was 0.261±0.005 kg oil extracted per kg of rice bran. A simulated economic analysis was performed on the possibility of using SC−CO₂ and propane extraction technologies to remove oil from rice bran generated in Mississippi. Although the economic analysis was based on the maximal extraction efficiency for each technology, neither process resulted in a positive rate of return on investment.     

Enzymatic extraction of mustard seed and rice bran

Aqueous enzymatic extraction was investigated for recovery of oil from mustard seed and rice bran. The extraction process was reproducible based on statistical analysis of extraction data under different extraction conditions. The most significant factors for extraction were the time of digestion with enzymes, seed or bran concentration in water, volume of hexane added before recovery, and amount of enzyme(s) used. The pretreatment steps of each material before enzyme digestion influenced oil yield. Quality of enzyme-extracted mustard oil was better with respect to color and odor than commercial expeller-extracted and Soxhlet-extracted oils. Most of the characteristics of rice bran oil were identical to those of commercial solvent-extracted oils, but rice bran oil had a lower content of colored substances and higher acidity (free fatty acid). Enzymatic extraction led to recovery of a protein concentrate with increased protein and reduced fiber and ash contents in the mustard and rice bran meals.     

Effect of Oils Extracted from Plant Seeds on the Growth and Lipolytic Activity of <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> Yeast

This study was aimed at evaluating the capability of Yarrowia lipolytica W29 for the synthesis of lipolytic enzymes in a medium containing plant oils from non‐conventional sources with some components displaying bioactivity. Oils from almond, hazelnut, and coriander seeds were obtained by using n‐hexane (Soxhlet method) and a chloroform/methanol mixture of solvents (Folch method), and their effect on the growth and lipolytic activity of Y. lipolytica was compared. A comparison of these two extraction methods showed that the extraction with n‐hexane was less effective regarding the oil extraction yields than the extraction conducted according to Folch's procedure. The lipolytic activity of the studied yeast was higher in the culture media containing oils extracted with the Soxhlet method than the Folch method but it was lower compared to olive oil medium. Among all oils tested, almond oil extracted with n‐hexane was the best inducer of extracellular lipases synthesized by Y. lipolytica. Its lipolytic activity achieved the maximum value of 2.33 U/mL after 48 h of culture. After 24 h of culture, it was close to the value obtained for the medium containing olive oil. Almond oil was a source of oleic and linoleic acids, which may determine differences in the lipolytic activity. The linoleic acid content in almond oil was higher than that found in other oils. When n‐hexane was used for extraction, the resultant oils were characterized by lower contents of polyphenols and poorer antioxidative activity.     

Enzymatic treatment of rice bran to improve processing

A modification of the process of oil extraction from rice bran is proposed, introducing one or two enzymatic reactions previous to solvent extraction. Although a total aqueous enzymatic extraction process did not result in reasonable oil extraction yields, an interesting alternative results from enzymatic reactions previous to solvent extraction or pressing. A thermal treatment of rice bran is first applied to deactivate lipase, but also to gelatinize starch previous to reaction with α-amylase. This is followed by a saccharifying step with glucoamylase to produce glucose (28 g/100 g of rice bran treated), while the residual paste, 66.7% of the original bran, may be subjected to a proteolytic process for protein extraction or directly treated with the solvent to obtain bran oil. Finally, under the defined extraction conditions using hexane, yields of oil are 5% higher when rice bran has been previously treated with α-amylase.     

Degumming,Dewaxing and Deacidification of Rice Bran Oil-Hexane Miscella Using Ceramic Membrane: Pilot Plant Study

An indigenously developed low-cost clay-alumina-based ceramic microfiltration membrane of 19-channel configuration has been evaluated for degumming, dewaxing and deacidification of rice bran oil (RBO) miscella having different oil contents at pilot scale. Rice bran wax and soap particles in miscella will aggregate with changes in temperature. This suggests a technique for their effective separation. Low-temperature cross-flow membrane filtration was used for single-stage degumming-dewaxing and showed 70 % and 80 % removal of acetone insoluble residue from two RBO miscella samples, respectively. Color reduction was 50 %, and oryzanol retention was 70 %. NaOH was used for deacidification in a 10 % excess of that required based on the free fatty acid content in oil. This reduced free fatty acids to 0.2 %. Operating for 10 h with a 0.7 bar trans-membrane pressure, permeate fluxes of 15 and 8 L/m² hr were obtained for the degumming-dewaxing and deacidification operations, respectively. The process has advantages, such as high micronutrient content (1.56 % oryzanol) and negligible oil loss (2.6 %). Moreover, ceramic membrane processing of RBO miscella could be an effective pre-treatment step with respect to micronutrient enrichment, elimination of heating, neutral oil recovery and a viable option for solvent separation.