Variables affecting the yields of methyl esters derived from in situ esterification of rice bran oil

The influence of specific factors on in situ methanolic esterification of rice bran oil (RBO) using sulfuric acid catalyst was investigated. using high-FFA rice bran was found to be the most effective means to increase methyl ester yields. The ester content of the extract increased about 67% when the FFA content of oil was increased from 16.6 to 84.5%. Increasing the reaction time beyond 30 min did not affect yields. Increasing the temperature from 20 to 65°C elevated the FAME yield by about 30%, but increasing the amount of acid catalyst above 5 mL did not enhance yield, and increasing the methanol dose from 200 to 250 mL had a negligible effect.     

FA monoalkylesters from rice bran oil by <Emphasis Type="Italic">in situ</Emphasis> esterification

Extraction and in situ esterification of rice bran oil with ethanol were investigated by studying the effects of rice bran oil FFA content and water content of ethanol. Ethyl ester formation in the ethanol phase increased as FFA content increased. Neutral oil solubility in this phase fell considerably, resulting in a high ethyl ester content. The decrease of the water content in ethanol led to an increase in neutral oil solubility in ethanol and promoted the equilibrium of reaction to ethyl-ester formation, resulting in lower FFA content of the product. The main factor that affected yield and monoester content when using high-acidity bran and various monohydroxy alcohols was the solubility of neutral oil in alcohol. The highest monoester content was obtained with methanol.     

Deacidification of high-acid rice bran oil by reesterification with monoglyceride

Autocatalytic esterification of free fatty acids (FFA) in rice bran oil (RBO) containing high FFA (9.5 to 35.0% w/w) was examined at a high temperature (210°C) and under low pressure (10 mm Hg). The study was conducted to determine the effectiveness of monoglyceride in esterifying the FFA of RBO. The study showed that monoglycerides can reduce the FFA level of degummed, dewaxed, and bleached RBO to an acceptable level (0.5±0.10 to 3.5±0.19% w/w) depending on the FFA content of the crude oil. This allows RBO to be alkali refined, bleached, and deodorized or simply deodorized after monoglyceride treatment to obtain a good quality oil. The color of the refined oil is dependent upon the color of the crude oil used.     

In situ production of fatty acid ethyl ester from low quality rice bran

Low quality rice bran with high free fatty acid content was utilized to produce fatty acid ethyl ester (FAEE) via in situ method. The effects of extraction solvent, acid and alkaline catalysts on the yield rate, esterification rate and transesterification rate were studied. About 12% (w_FAEE/w_rice-bran) of FAEE was obtained when absolute ethanol was used as solvent to extract rice bran oil. The esterification rate and transesterification rate reached 98% and 83%, respectively. With the aid of petroleum ether, the yield rate of FAEE could be improved to 16% (w_FAEE/w_rice-bran), and the esterification rate and transesterification rate reached 99% and 86%. Hydrophobic CaCO₃ nanorods were also synthesized as value-added byproduct. Based on the proposed method, the production process of FAEE could be simplified and the production cost could be reduced.     

Extraction and purification of oryzanol from rice bran oil and rice bran oil soapstock

Oryzanol is an important value-added co-product of the rice and rice bran-refining processes. The beneficial effects of oryzanol on human health have generated global interest in developing facile methods for its separation from rice bran oil soapstock, a by-product of the chemical refining of rice bran oil. In this article we discuss the isolation of oryzanol and the effect that impurities have on its extraction and purification. Presented are the principles behind the extraction (solid-liquid or liquid-liquid extraction, and other methods) of these unit operations covered in selected patents. Methods other than extraction such as crystallization or precipitation-based or a combination of these unit operations also are reviewed. The problems encountered and the ways to solve them during oryzanol extraction, such as prior processing and compositional variation in soapstock, resistance to mass transfer, moisture content and the presence of surface active components, which cause emulsion formation, are examined. Engineering inputs required for solving problems such as saponification, increasing mass transfer area, and drying methods are emphasized. Based on an analysis of existing processes, those having potential to work in large-scale extraction processes are presented.     

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     

Purification and identification of rice bran oil fatty acid steryl and wax esters

Fatty acid steryl esters (FASE) and wax esters (WE) of rice bran oil (RBO) have potential applications in cosmetic, nutraceutical, and pharmaceutical formulations. FASE and WE were extracted from RBO by a modified Soxhlet extraction using hexane as the solvent. FASE and WE were then separated by storage in acetone at 10°C for 24 h. The FASE fraction was further purified by silica, gel column chromatography. The contents and compositions of FASE and WE, as well as their saponified products, were identified by GC and GC-MS. The identification of FASE and WE was carried out by comparing the retention time of GC peaks and mass spectral analysis with standards synthesized in our laboratory. FASE and WE accounted for ca. 4.0% of crude RBO, of which 2.8–3.2% and 1.2–1.4% are FASE and WE, respectively. GC-MS of FASE showed five major peaks. Major FA in the FASE fraction were linoleic acid and oleic acid, which were esterified with 4-desmethyl, 4-monomethyl, and 4,4-dimethyl sterols. The contents of 4-desmethylsterol, 4-monomethylsterol, and 4,4-dimethylsterol esters in crude RBO were 76.1, 8.7, and 15.1%, respectively. WE of RBO consisted of both even and odd carbon numbers ranging from C₄₄ to C₆₄. The major constituents were, saturated esters of C₂₂ and C₂₄ FA and C₂₄ to C₄₀ aliphatic alcohols, with C₂₄ and C₃₀ being the predominant FA and fatty alcohol, respectively. The advantages of using a modified Soxhlet extraction over column chromatography are less solvent usage and larger sample size per batch with shorter operation time.     

Genetic diversity for lipid content and fatty acid profile in rice bran

Rice (Oryza sativa L.) bran contains valuable nutritional constituents, which include lipids with health benefits. A germplasm collection consisting of 204 genetically diverse rice accessions was grown under field conditions and evaluated for total oil content and fatty acid (FA) composition. Genotype effects were highly statistically significant for lipid content and FA profile (P<0.001). Environment (year) significantly affected oil content (P<0.05), as well as stearic, oleic, linoleic, and linolenic acids (all with P<0.01 or lower), but not palmitic acid. The oil content in rice bran varied relatively strongly, ranging from 17.3 to 27.4% (w/w). The major FA in bran oil were palmitic, oleic, and linoleic acids, which were in the ranges of 13.9–22.1, 35.9–49.2, and 27.3–41.0%, respectively. The ratio of saturated to unsaturated FA (S/U ratio) was highly related to the palmitic acid content (r ²=0.97). Japonica lines were characterized by a low palmitic acid content and S/U ratio, whereas Indica lines showed a high palmitic acid content and a high S/U ratio. The variation found suggests it is possible to select for both oil content and FA profile in rice bran.     

Evaluation of the stability of blends of sunflower and rice bran oil

Blends of sunflower oil (SFO) and rice bran oil (RBO) were evaluated for their stability. Additionally, known amounts of natural antioxidants extracted from RBO were added to SFO, and their protective effect was compared to that of the blends. The results found indicate that by raising the amount of RBO, from 10 to 50%, an increase of OLO, OLP, PPL, OOO, PPO, OPO, 18:1 and 16:0 occurred, followed by a decrease of LLL, LLO, and 18:2. These changes in fatty acid and triacylglycerol (TAG) composition led to an increase of the oil stability index at 120 °C and a reduction of polymer TAG formation in the heated blends at 180 °C during 8 h. A comparable protective effect of natural antioxidants to that of blending was observed in a 50 : 50 blend, by remarkably increasing the induction period.     

Lipase‐catalyzed production of biodiesel from rice bran oil

Biodiesel has attracted considerable attention as an alternative fuel during the past decades. The main hurdle to the commercialization of biodiesel is the cost of the raw material. Use of an inexpensive raw material such as rice bran oil is an attractive option to lower the cost of biodiesel. Two commercially available immobilized lipases, Novozym 435 and IM 60, were employed as catalyst for the reaction of rice bran oil and methanol. Novozym 435 was found to be more effective in catalyzing the methanolysis of rice bran oil. Methanolysis of refined rice bran oil and fatty acids (derived from rice bran oil) catalyzed by Novozym 435 (5% based on oil weight) can reach a conversion of over 98% in 6 h and 1 h, respectively. Methanolysis of rice bran oil with a free fatty acid content higher than 18% resulted in lower conversions (<68%). A two‐step lipase‐catalyzed methanolysis of rice bran oil was developed for the efficient conversion of both free fatty acid and acylglycerides into fatty acid methyl ester. More than 98% conversion can be obtained in 4–6 h depending on the relative proportion of free fatty acid and acylglycerides in the rice bran oil. Inactivation of lipase by phospholipids and other minor components was observed during the methanolysis of crude rice bran oil. Simultaneous dewaxing/degumming proved to be efficient in removing phospholipids and other minor components that inhibit lipase activity from crude rice bran oil. Copyright © 2005 Society of Chemical Industry     

In situ production of fatty acid methyl ester from low quality rice bran: An economical route for biodiesel production

Low quality rice bran was used to produce fatty acid methyl ester (FAME) via in situ extraction, esterification and transesterification process. The effects of the acid and alkaline catalysts on the ester yield, esterification and transesterification process were studied. When 75 ml of absolute methanol, 150 ml of petroleum ether, 0.75 g of concentrated sulfuric acid and 0.71 g of sodium hydroxyl were used, 16.69% (w_FAME/w_{rice bran}) of FAME was obtained. The esterification rate and the transesterification rate reached 98.83% and 80.47%. Based on the proposed route, the production process of FAME (biodiesel) could be simplified and the production cost could be reduced.     

Use of rice bran oil and epoxidized rice bran oil in carbon black–filled natural rubber–polychloroprene blends

In the present study we report the results obtained on the use of rice bran oil (RBO), a naturally occurring nontoxic oil, and its epoxidized variety (epoxidized RBO, or ERBO) in the compounding and vulcanization of different natural rubber–chloroprene rubber (NR–CR) blends. The processability, cure characteristics, and physical properties of the blends prepared with these oils were compared with those of control mixes prepared with aromatic oil. The optimum cure time and scorch time values of the different blends prepared with these oils were found to be lower than those of the respective control blends prepared with aromatic oil. Evaluation of physical properties of the different experimental blends showed that replacement of aromatic oil with these oils did not adversely affect their physical properties. Because RBO contains a good amount of free fatty acids it was tried as a coactivator in addition to its role as a processing aid. The level of these oils required for the blend preparation was optimized in a Brabender plasticorder. Physical properties such as tensile strength, elongation at break, tear strength, swelling index, and abrasion loss, for example, were evaluated for both experimental and control mixes. Comparison of cure characteristics and physical properties of the blends prepared with aromatic oil and with these oils showed that these oils could be used in place of aromatic oil in the above blends. It is also to be noted that aromatic oil is of petroleum origin and is reported to be carcinogenic. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4084–4092, 2003     

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.     

Study on the composition of rice bran oil and its higher free fatty acids value

The compositions of rice bran oils (RBO) and three commercial vegetable oils were investigated. For refined groundnut oil, refined sunflower oil, and refined safflower oil, color values were 1.5–2.0 Lovibond units, unsaponifiable matter contents were 0.15–1.40%, tocopherol contents were 30–60 mg%, and FFA levels were 0.05–0.10%, whereas refined RBO samples showed higher values of 7.6–15.5 Lovibond units for color, 2.5–3.2% for unsaponifiable matter, 48–70 mg% for tocopherols content, and 0.14–0.55% for FFA levels. Of the four oils, only RBO contained oryzanol, ranging from 0.14 to 1.39%. Highoryzanol RBO also showed higher FFA values compared with the other vegetable oils studied. The analyses of FA and glyceride compositions showed higher palmitic, oleic, and linoleic acid contents than reported values in some cases and higher partial glycerides content in RBO than the commonly used vegetable oils. Consequently, the TG level was 79.9–92% in RBO whereas it was >95% in the other oils studied. Thus, refined RBO showed higher FFA values, variable oryzanol contents, and higher partial acylglycerol contents than commercial vegetable oils having lower FFA values and higher TG levels. The higher oryzanol levels in RBO may contribute to the higher FFA values in this oil.     

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.     

Deacidifying rice bran oil by solvent extraction and membrane technology

Crude rice bran oil containing 16.5% free fatty acids (FFA) was deacidified by extracting with methanol. At the optimal ratio of 1.8:1 methanol/oil by weight, the concentration of FFA in the crude rice bran oil was reduced to 3.7%. A second extraction at 1:1 ratio reduced FFA in the oil to 0.33%. The FFA in the methanol extract was recovered by nanofiltration using commercial membranes. The DS-5 membrane from Osmonics/Desal and the BW-30 membrane from Dow/Film Tec gave average FFA rejection of 93–96% and an average flux of 41 L/m²·h (LMH) to concentrate the FFA from 4.69% to 20%. The permeate, containing 0.4–0.7% FFA, can be nanofiltered again to recover more FFA with flux of 67–75 LMH. Design estimates indicate a two-stage membrane system can recover 97.8% of the FFA and can result in a final retentate stream with 20% FFA or more and a permeate stream with negligible FFA (0.13%) that can be recycled for FFA extraction. The capital cost of the membrane plant would be about $48/kg oil processed/h and annual operating cost would be about $15/ton FFA recovered. The process has several advantages in that it does not require alkali for neutralization, no soapstock nor wastewater is produced, and effluent discharges are minimized.     

Nutrition of rice bran oil in relation to its purification

A comparative nutritive study was made to show that the extent of purification markedly influences the nutritive characteristics of rice bran oil. The coefficient of digestibility was 93.8% when rice bran oil that had been purified by degumming, deacidifying, bleaching and deodorizing was fed to rats; whereas it was 94.8% when extremely pure rice bran oil, which was achieved by including an additional dewaxing step, was used. Rice bran oil without deodorization, but purified by other treatments, showed a 96.2% coefficient of digestibility, which is somewhat lower than that of groundnut oil. However, after a feeding experiment over three months, the highly purified rice bran oil showed better results than the other two purified samples of rice bran oil, and was sometimes better than groundnut oil in terms of total lipid, triglyceride and especially in cholesterol content in serum, liver and heart tissues.     

Continual conversion of free fatty acid in rice bran oil to triacylglycerol by immobilized lipase

Rice bran oil containing 30–50% free fatty acid was continually converted to an oil containing more than 75% of triacylglycerol (TG) by means of immobilized lipase. The reaction was carried out at 60°C for 24 h with dehydration and reactant mixing by dry nitrogen flow under a positive nitrogen atmosphere. Enzymatic TG synthesis with evaporation by heating was not suitable because of the increasing peroxide value of the oil. Part of this article was presented at the annual meeting of the Japan Oil Chemists' Society at Sendai, Japan, October, 16, 1990.     

Zero-<Emphasis Type="Italic">trans</Emphasis> shortening using palm stearin and rice bran oil

Several pilot-scale trials reported in this paper, using palm stearin-rice bran oil (PS-RBO) blends, obviously did not contain trans FA (TFA), whereas the commercial products were found to contain 18–27% TFA. The effects of processing conditions such as rate of agitation, crystallization temperature, and composition of the blends on the crystal structure of shortenings were studied. The products were evaluated for their physicochemical characteristics using DSC, X-ray diffraction (XRD), HPLC, and FTIR techniques. The formulation containing 50% PS and 50% RBO showed melting and cooling characteristics similar to those of hydrogenated commercial “vanaspati” samples. Analysis of the FA composition revealed that the formulated shortenings contained 15–19% C_18∶2 PUFA. Tocopherol and tocotrienol contents of the experimental shortenings were in the range of 850–1000 ppm with oryzanol content up to 0.6%. XRD studies demonstrated that the crystal form in the shortenings was predominantly the most stable β′ form, and there was less of the undesirable β form.