Quantitative analysis of fatty acids and sterols in Malagasy rice bran oils

The fatty acid and sterol compositions of six Malagasy rice bran oils were evaluated. Investigation by gas liquid chromatography (GLC) using Carbowax 20 M revealed 10 fatty acids, mainly palmitic (16–20%) oleic (41–44%) and linolenic (31–37%) acids. An OV 17 column was used to separate eight sterols, mainly Β-sitosterol (53–59%), campesterol (16–26%) and stigmasterol (10–13%). No significant variation for the fatty acid and sterol contents was observed among the rice varieties studied.     

Rice bran oil. V. The stability and processing characteristics of some rice bran oils

1. The extraction, processing, characteristics, and stability properties of nine batches of hexane-extracted rice bran oil were investigated. The oils were refined, bleached, and deodorized and their color and stability determined. Samples of the bleached oils were hydrogenated to approximately shortening consistency, deodorized, and the stability of the hydrogenated products determined.
2. Pilot plant extractions of five batches of rice bran yielded crude oils equivalent to 91% of the hexane-soluble portions of the bran.
3. The nine crude oils whose content of free fatty acids ranged from 2.0 to 6.3% were refined by the cup method with losses ranging from 12.0 to 23.5% although the neutral oil content of six crude rice bran oils ranged from 89.9 to 92.6%.
4. The Lovibond color of the nine refined oils ranged from 35 yellow and 4.5 red to 70 yellow and 9.5 red, and the color of the bleached oils ranged from 15 yellow and 1.5 red to 35 yellow and 3.2 red.
5. Steam-refining, employed in conjunction with alkali-refining, proved effective as a means of reducing the losses in refining rice bran oil.
6. The nine batches of refined, bleached, and deodorized rice bran oils had iodine values ranging from 101.3 to 105.7 and stabilities averaging 24 hours.
7. Nine bleached oils hydrogenated to approximate shortening consistency had iodine values averaging approximately 66 and stabilities averaging 370 hours.
8. Refined, bleached, and deodorized rice bran oil is bland but has some tendency toward flavor reversion.
9. The most outstanding characteristics of rice bran oil is its exceptional stability after hydrogenation.

     

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.     

The sterols ofCucurbita moschata (“calabacita”) seed oil

From the sterol fraction of seed oil from commercialCucurbita moschata Dutch (“calabacita”) Δ⁵ and Δ⁷ sterols having saturated and unsaturated side chain were isolated by chromatographic procedures and characterized by spectroscopic (¹H and¹³C-nuclear magnetic resonance, mass spectrometry) methods. The main components were identified as 24S-ethyl 5α-cholesta-7,22E-dien-3β-ol (α-spinasterol); 24S-ethyl 5α-cholesta-7,22E, 25-trien-3β-ol (25-dehydrochondrillasterol); 24S-ethyl 5α-cholesta-7, 25-dien-3β-ol; 24R-ethylcholesta-7-en-3β-ol (Δ⁷-stigmastenol) and 24-ethyl-cholesta-7, 24(28)-dien-3β-ol (Δ^7,24(28)-stigmastadienol).Lipids 31, 1205–1208 (1996).     

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.     

Biorefining of high acid rice bran oil

Rice bran oil with a high free fatty acid content (FFA) after degumming and dewaxing can be converted into edible quality oil of satisfactory refining characteristics by first adopting the biorefining process to reduce the major portion of the FFA by converting them into neutral glycerides with the aid of 1,3-specific lipase under optimum conditions and later deacidifying the residual FFA of the biorefined oil by alkali neutralization.     

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     

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.     

Epoxidized rice bran oil (ERBO) as a plasticizer for poly(vinyl chloride) (PVC)

With environmental and toxicity concerns becoming more critical, there are increasing efforts to remove phthalates from polymer compounds around the globe more rapidly. Phthalates can be replaced by natural products; in particular, those obtained from vegetable oils and fats. In the present study, a natural-based plasticizer, synthesized by epoxidation of non-toxic rice bran oil (RBO) with peroxy acid generated in situ has been added to poly(vinyl chloride). The influence of various reaction parameters on epoxidation was studied by investigating the reaction ratio, temperature, reaction time and stirring speed. Epoxidized rice bran oil (ERBO) obtained from an optimized reaction condition was analyzed by iodine number and oxirane content. FTIR was used to analyze epoxy group formation. Product ERBO was obtained with 82 % oxirane conversion within 3 h of reaction period. PVC sheets were formulated using a conventional plasticizer di-(octyl) phthalate and was partially replaced by synthesized ERBO. The effect of ERBO addition was tested by mechanical properties (tensile strength, modulus, elongation-at-break, shore D hardness) and compared with commercially available ESBO (epoxidized soybean oil). ERBO presented fairly good incorporation and plasticizing performance, as demonstrated by the results of mechanical properties, exudation, migration tests, thermal stability by thermogravimetric analysis, T _g values as shown by differential scanning calorimetry, replacing about 60 % of the total plasticizer.     

Sterols of the spongeTethya amamensis: Occurrence of (24E)-24-ethylidenecholesta-5,7-dienol, (24E)-24-propylidenecholesta-5,7-dienol,and (24Z)-24-propylidenecholesta-5,7-dienol

The spongeTethya amamensis, collected from Kagoshima Bay, Japan, contained at least 24 sterols, including Δ⁵-sterols (82.2% of total sterols) and Δ^{5, 7}-sterols (17.8%). The predominant sterols were cholesterol (29.0%), cholesta-5,22-dienol (13.8%), 24-methylcholesta-5,22-dienol (10.9%), 24-methylenecholesterol (8.3%), 24-methylcholesta-5,7,22-trienol (6.8%), 24-ethylcholest-5-enol (6.1%), and isofucosterol *4.1%). Combined gas liquid chromatography-mass spectrometry suggested the presence of 3 uncommon sterols, (24E)-24-ethylidenecholesta-5,7-dienol, (24E)-24-propylidenecholesta-5,7-dienol, and (24Z)-24-propylidenecholesta-5,7-dienol as minor components. The sterols ofT. amamensis also contained small amounts of 24-norcholesta-5,7,22-trienol and (24Z)-24-ethylidenecholesta-5,7-dienol.     

Occurrence of conjugated fatty acids in the seed oil ofcouepia longipendula (chrysobalanaceae)

The seeds ofCouepia longipendula contain 74.2% oil. Gas chromatography (GC) and gas chromatography/ mass spectrometry (GC/MS) of the methyl esters and oxazoline derivatives of the fatty acids and ultraviolet (UV), infrared (IR),¹H-nuclear magnetic resonance (NMR) and¹³C-NMR spectra of the oil showed the presence of palmitic (25.2%), palmitoleic (0.9%), stearic (6.2%), oleic (26.5%), vaccenic (0.4%), linoleic (7.4%), arachidic (0.3%), α-eleostearic (11.3%) and α-licanic (21.8%) acids. Licanic acid methyl ester was isolated by thin-layer chromatography (TLC) and the¹³C-NMR and¹H-NMR data are presented.     

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.     

A method for the separation of seed oil steryl esters and free sterols: Application to peanut and corn oils

A method for separating and quantitating seed oil steryl esters and free sterols was developed using a combination of preparative column, thin layer (TLC), and gas liquid chromatography (GLC). Cholesteryl heneicosanoate and cholesterol served as internal standards. The method was applied to corn-oil samples (Mazola, Kroger) obtained from the local market and peanut-oil samples prepared in the laboratory from commercial varieties of peanuts (Florunner, Starr). Concentration (mg/100 g oil; mean ± SD) of steryl esters and free sterols in the 4 oils were: Mazola, 1420±40 and 370±8; Kroger, 950±40 and 320±4; Florunner, 74±0.5 and 150±3; and Starr, 51±0.5 and 130±2. Sitosterol was the major sterol in both the free sterol and steryl ester fractions of all oils and together with campesterol, stigmasterol and Δ⁵-avenasterol made up 90–95% of all sterols. Steryl esters of peanut oil contained higher proportions of linoleic acid and long-chain acids (C₂₀–C₂₄) than did whole oil. Corn-oil steryl esters also contained a higher proportion of linoleic acid than did whole oil. Squalene was the major hydrocarbon of all oils with the remaining hydrocarbon fraction consisting of a mixture of compounds. Presented at the AOCS meeting, Toronto, May 1982.     

Spectrophotometric studies of rice bran oil and mustard oil mixtures: I

Visible spectra between 520\s-700 nm of unbleached mustard oil, rice bran oil and their 10 mixtures are reported. Mustard oil shows its characteristic band at 671.5 nm, and rice bran oil shows two characteristic bands at 550 and 564 nm and a contour centered at about 656 nm. The 564 nm band starts emerging in mixtures even by the 5% presence of rice bran oil and takes its well resolved shape at higher ratios. The 671.5 nm mustard oil band shows uniform hypsochromic shift up to 40% of rice bran oil, and at higher concentrations this shifting becomes irregular. An approximate estimation of rice bran oil adulteration in mustard oil can be made by observing the shifted position of 671.5 nm band.     

An investigation of rice bran oil tank settling

A wax-like settling is observed in tanks in which rice bran oil is stored. “Soft” and “hard” wax fractions have been isolated from this settling by solvent Crystallization. Previous investigation has shown that the settling consists mainly of wax esters of long chain alcohols and long chain fatty acids. The present work describes the column chromatographic analysis of unhydrolyzed tank settling. The presence of an aromatic moiety is indicated in the infra red spectrum. Comparison of data obtained by analysis of the tank settling before and after hydrolysis shows that it contains only 33% of monomeric esters; the remainder may be present as a polymeric ester, as found in carnauba wax. Investigation of different samples of rice bran oil has shown that the ratio of monomeric to polymeric fraction varies with the history of the bran.     

Spectrophotometric studies of rice bran oil and mustard oil mixtures: II

Visible spectra, between 400 to 500 nm range, of rice bran oil, mustard oil and their 7 mixtures, diluted 10 times in carbon tetrachloride, are reported. Mustard oil spectra shows three characteristic bands centered at wavelength 428, 453 and 482 nm, while no such band has been observed in rice bran oil spectra in this range. Intensity of 428 nm band increases as the rice bran oil percentage increases in the mixture of two oils. Five indices, R₁ to R₅, have been suggested for the approximate determination of rice bran oil adulteration in mustard oil. Plots of R₂ and R₃ against percentage of rice bran oil in the mixture have been found to be straight lines. The index R₃, equal to 1000(A₄₂₈-A₄₈₂), has been found to be the most useful for this approximate estimation of rice brain oil in mustard 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.     

The content and composition of sterols and sterol esters in sunflower and poppy seed oils

The composition and proportion of free sterols and sterol esters in crude sunflower and poppy seed oils were determined, using preparative thin layer chromatography followed by gas chromatography with cholesterol as an internal standard. Free sterols and sterol esters were also isolated in a liquid fraction obtained by low temperature crystallization (−80 C) of the oils and enriched with minor lipid classes. This enrichment procedure provided a liquid fraction suitable for studies of minor components in the oils. However, selectivity towards sterol esters was observed since sterols esterified to very long chain fatty acids (C₂₀–C₂₄) were preferentially retained in the precipitate. The proportions of free and esterified sterols were found to be 0.34 and 0.28%, respectively, in the sunflower oil, whereas the corresponding figures for poppy seed oil were 0.33% and 0.05%. Sunflower oil was characterized by a relatively high percentage of Δ7-sterols, preferentially obtained in the esterified fraction, and by very long chain saturated fatty acids of sterol esters. The sterols in poppy seed oil were composed almost entirely of campesterol, stigmasterol, sitosterol and Δ5-avenasterol, although their percentage distributions were remarkably different in the free and esterified fraction.