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。     

Effect of refining of crude rice bran oil on the retention of oryzanol in the refined oil

The effect of different processing steps of refining on retention or the availability of oryzanol in refined oil and the oryzanol composition of Indian paddy cultivars and commercial products of the rice bran oil (RBO) industry were investigated. Degumming and dewaxing of crude RBO removed only 1.1 and 5.9% of oryzanol while the alkali treatment removed 93.0 to 94.6% of oryzanol from the original crude oil. Irrespective of the strength of alkali (12 to 20° Be studied), retention of oryzanol in the refined RBO was only 5.4–17.2% for crude oil, 5.9–15.0% for degummed oil, and 7.0 to 9.7% for degummed and dewaxed oil. The oryzanol content of oil extracted from the bran of 18 Indian paddy cultivars ranged from 1.63 to 2.72%, which is the first report of its kind in the literature on oryzanol content. The oryzanol content ranged from 1.1 to 1.74% for physically refined RBO while for alkali-refined oil it was 0.19–0.20%. The oil subjected to physical refining (commercial sample) retained the original amount of oryzanol after refining (1.60 and 1.74%), whereas the chemically refined oil showed a considerably lower amount (0.19%). Thus, the oryzanol, which is lost during the chemical refining process, has been carried into the soapstock. The content of oryzanol of the commercial RBO, soapstock, acid oil, and deodorizer distillate were in the range: 1.7–2.1, 6.3–6.9, 3.3–7.4, and 0.79%, respectively. These results showed that the processing steps—viz., degumming (1.1%), dewaxing (5.9%), physical refining (0%), bleaching and deodorization of the oil—did not affect the content of oryzanol appreciably, while 83–95% of it was lost during alkali refining. The oryzanol composition of crude oil and soapstock as determined by high-performance liquid chromatography indicated 24-methylene cycloartanyl ferulate (30–38%) and campesteryl ferulate (24.4–26.9%) as the major ferulates. The results presented here are probably the first systematic report on oryzanol availability in differently processed RBO, soapstocks, acid oils, and for oils of Indian paddy cultivars.     

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     

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.     

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.     

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.     

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.     

Physical refining of rice bran oil in relation to degumming and dewaxing

Physical refining of rice bran oil (RBO) with acidity between 4.0 and 12.4% has been investigated in relation to degumming and dewaxing pretretments. It appears that physical refining after combined low-temperature (10°C) degumming-dewaxing produces good-quality RBO with respect to color, free fatty acid, oryzanol, and tocopherol content.     

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.     

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.     

Influence of viscosity on wax settling and refining loss in rice bran oil

The role of viscosity on was settling and refining loss in rice bran oil (RBO) has been studied with model systems of refined peanut oil and RBO of different free fatty acids contents. Wax was the only constituent of RBO that significantly increased the viscosity (81.5%) of oil. Monoglycerides synergistically raised the viscosity of the oil (by 114.2%) and lowered the rate of wax settling. Although a reduction in the viscosity of the oil significantly decreased the refining loss, the minimum loss attained was still 20% more than the theoretically predicted value. This led us to conclude that some chemical constituents, such as monoglycerides, must be removed before dewaxing; thereafter, oryzanol and phospholipids have to be removed. One can get an oil free of wax, recover other by-products and reduce processing losses.     

A novel process for physically refining rice bran oil through simultaneous degumming and dewaxing

A new process for the physical refining of rice bran oil through combined degumming and dewaxing was developed on a laboratory scale and then demonstrated on a commercial scale. The simultaneous degumming and dewaxing of the crude oil with a solution of water and CaCl₂, followed by crystallization at a low temperature (20°C), facilitated precipitation of the hydratable and nonhydratable phosphatides along with the wax, which enabled its separation and reduction to a greater extent. Bleaching and subsequent winterization (20°C) of this oil further reduced the phosphorus content to less than 5 ppm. Thus, these pretreatment steps enabled the physically refined rice bran oil to meet commercially acceptable levels for color, FFA content, and cloud point values (10–12 Lovibond units in a 1-in, cell, <0.25%, and 4–5°C, respectively) with very low neutral oil loss; this has not been observed hitherto. Rice bran oil is known for its high levels of bioactive phytochemicals, such as oryzanol, tocols, and sterols. The process reported here could retain more than 80% of these micronutrients in the end product. This paper was previously presented at the 95th AOCS Annual Meeting and Expo, Cincinnati, Ohio, May 9–12, 2004     

Origin of problems encountered in rice bran oil processing

Rice bran oil, not being a seed‐derived oil, has a composition qualitatively different from common vegetable oils and the conventional vegetable oil processing technologies are not adaptable without incurring huge losses. The oil's unusual high content of waxes, free fatty acids, unsaponifiable constituents, phospholipids, glycolipids and its dark color, all cause difficulties in the refining process. An attempt was made in this investigation to look into factors that are responsible for such difficulties and to develop suitable methodologies for physical refining of rice bran oil. Special attention was given to dewaxing, degumming and deacidification steps. The high content of glycolipids (∼6%) present in the oil was found to be a central problem and their removal appeared crucial for successful processing of the oil. We have also isolated and identified, for the first time, phosphorus‐containing glycolipids that are unique to this oil. These compounds prevent a successful degumming of the oil and their high surface activity leads to unusually high refining losses during alkali refining. A number of simple processes has been evolved, including 1) a simultaneous dewaxing and degumming process, 2) an unusual enzymatic process to degum the oil, 3) processes for the removal of the glycolipids including the phosphoglycolipids and 4) a process for the isolation of the glycolipids which may have potential applications in the food, cosmetic and pharmaceutical industries. The processing protocol suggested here becomes the first and only one to produce an oil with less than 5 ppm of phosphorus from crude rice bran oil, rendering it thus suitable for physical refining. We believe that the present results are very significant and should contribute to a better utilization of this valuable oil.     

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.     

Influence of chemical refining on the major and minor components of rice brain oil

The effects of each individual step of the chemical refining process on major and minor components of rice bran oil were examined. In comparison with common vegetable oils, rice brain oil contains a significantly higher level of several bioactive minor components such as γ-oryzanol, tocotrienols, and phytosterols. Alkali treatment or neutralization results in a significant loss of oryzanol. In addition, it gives rise to a change in the individual phytosterol composition. After bleaching, some isomers of 24-methylenecycloartanol were detected. Because of their relatively high volatility, phytosterols and tocotrienols are stripped from the rice brain oil during deodorization and concentrated in the deodorizer distillate. At the same time, oryzanol is not volatile enough to be stripped during deodorization; hence, the oryzanol concentration does not change after deodorization. Complete refining removed 99.5% of the FFA content. Depending on the applied deodorization conditions, trans FA can be formed, but the total trans content generally remains below 1%.     

Enzyme‐assisted water‐extraction of oil and protein from rice bran

Enzymatic water‐extraction of oil and proteins from rice bran was studied in a laboratory‐scale set‐up. The effects of the following enzymes – Celluclast 1.5L, hemicellulase, Pectinex Ultra SP‐L, Viscozyme L, Alcalase 0.6L and papain – on oil and protein extraction yields, and the level of reducing sugars in the extract were investigated. The results showed that Alcalase was most effective in enhancing oil and protein extraction yields. Papain was found to be superior to all carbohydrase enzymes but it gave lower yields than Alcalase. Celluclast 1.5L, hemicellulase, Pectinex Ultra SP‐L and Viscozyme L did not affect yields significantly but increased the level of reducing sugars in the extract. © 2002 Society of Chemical Industry     

Recovery of γ-oryzanol from rice bran oil byproduct using supercritical fluid extraction

The residue of fatty acids distillation from rice bran oil soapstock (RFAD-RBOS) is a byproduct from rice bran oil industry. It contains a large amount of γ-oryzanol, which is a valuable antioxidant. The main objective of this work was to investigate the recovery of γ-oryzanol from the RFAD-RBOS using supercritical fluid extraction (SFE). The Soxhlet technique was conducted in order to compare results with SFE. The influence of process parameters over SFE was evaluated in terms of global yield, γ-oryzanol content, γ-oryzanol recovery rate, and fatty acids composition. The mathematical modeling of SFE overall extraction curve (OEC) was also investigated. The condition of 30 MPa/303 K presented the maximum global yield (39 ± 1%, w/w), maximum γ-oryzanol recovery rate (31.3%, w/w), relatively high γ-oryzanol content (3.2%, w/w), and significant presence of monounsaturated and polyunsaturated fatty acids. The logistic model presented the best fit to experimental OEC.     

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     

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.     

Determination of nonvolatile components in polar fractions of rice bran oils

High-oryzanol rice brain oil (HORBO), rice bran oil (RBO), and partially hydrogenated soybean oil (PHSBO) were used to prepare french fries. Polar fractions of the three oils were analyzed for nonvolatile components by high-performance size-exclusion chromatography (HPSEC) with ELSD. In all frying experiments, both HORBO and RBO yielded predominantly dimeric and monomeric materials. The concentrations of polymeric species in HORBO and RBO were greater than in PHSBO. The major degradation products from HORBO, RBO, and PHSBO were dimers (8.93 mg/100 mg oil), monomers (10.5 mg/100 mg oil), and DG (22.4 mg/100 mg oil), respectively. Thermal degradation via hydrolysis was much greater in PHSBO than in HORBO or RBO. Distribution data indicated that the extent of polymer formation from frying was in the order RBO>HORBO >PHSBO, consistent with the degree of lipid unsaturation and the oryzanol content in these oils. HPSEC-ELSD results from the two RBO showed that the amounts of various polymeric species, including trimers and higher polymers, were lower in HORBO than in RBO. The percentage of polar materials and the percentage of polymerized TG, which were used as indicators of oil quality and stability, decreased with increasing tocopherol and oryzanol contents in the order PHSBO>HORBO>RBO.