Comparison of Soybean and Cottonseed Oils upon Hydrogenation with Nickel,Palladium and Platinum Catalysts

There is current interest in reducing the trans fatty acids (TFA) in hydrogenated vegetable oils because consumption of foods high in TFA has been linked to increased serum cholesterol content. In the interest of understanding the TFA levels, hydrogenation was carried out in this work on soybean oil and cottonseed oil at two pressures (2 and 5 bar) and 100 °C using commercially available Ni, Pd, and Pt catalysts. The TFA levels and the fatty acid profiles were analyzed by gas chromatography. The iodine value of interest is ~70 for all-purpose shortening and 95–110 for pourable oil applications. In all cases, higher hydrogen pressures produced lower levels of TFA. In the range of 70–95 iodine values for the hydrogenated products, the Pt catalyst gave the least TFA, followed closely by Ni, and then Pd, for both oils. For all three catalysts at 2- and 5-bar pressures and 70–95 iodine values, cottonseed oil contained noticeably less TFA than soybean oil; this is probably because cottonseed oil contains a lower total amount of olefin-containing fatty acids relative to soybean oil. Approximate kinetic modeling was also done on the hydrogenation data that provided additional confirmation of data consistency.     

Electrochemical hydrogenation of edible oils in a solid polymer electrolyte reactor. Sensory and compositional characteristics of low Trans soybean oils

Soybean oils were hydrogenated either electrochemically with Pd at 50 or 60°C to iodine values (IV) of 104 and 90 or commercially with Ni to iodine values of 94 and 68. To determine the composition and sensory characteristics, oils were evaluated for triacylglycerol (TAG) structure, stereospecific analysis, fatty acids, solid fat index, and odor attributes in room odor tests. Trans fatty acid contents were 17 and 43.5% for the commercially hydrogenated oils and 9.8% for both electrochemically hydrogenated products. Compositional analysis of the oils showed higher levels of stearic and linoleic acids in the electrochemically hydrogenated oils and higher oleic acid levels in the chemically hydrogenated products. TAG analysis confirmed these findings. Monoenes were the predominant species in the commercial oils, whereas dienes and saturates were predominant components of the electrochemically processed samples. Free fatty acid values and peroxide values were low in electrochemically hydrogenated oils, indicating no problems from hydrolysis or oxidation during hydrogenation. The solid fat index profile of a 15∶85 blend of electrochemically hydrogenated soybean oil (IV=90) with a liquid soybean oil was equivalent to that of a commercial stick margarine. In room odor evaluations of oils heated at frying temperature (190°C), chemically hydrogenated soybean oils showed strong intensities of an undesirable characteristic hydrogenation aroma (waxy, sweet, flowery, fruity, and/or crayon-like odors). However, the electrochemically hydrogenated samples showed only weak intensities of this odor, indicating that the hydrogenation aroma/flavor would be much less detectable in foods fried in the electrochemically hydrogenated soybean oils than in chemically hydrogenated soybean oils. Electrochemical hydrogenation produced deodorized oils with lower levels of trans fatty acids, compositions suitable for margarines, and lower intensity levels of off-odors, including hydrogenation aroma, when heated to 190°C than did commercially hydrogenated oil.     

Polymorphic behavior of high-melting glycerides from hydrogenated canola oil

Canola oil was hydrogenated with a commercial nickel catalyst at 175°C and 15 psi hydrogen pressure. Samples were taken during the reaction starting at 15 min and thereafter at ten-minute intervals. The reaction was stopped after two hours. The high-melting glycerides (HMG) were obtained by fractional crystallization at 15°C with acetone as solvent. The HMG were analyzed for fatty acid and triglyceride composition by gas liquid chromatography andtrans was determined by infrared spectroscopy. In the first 45 min of hydrogenation of canola oil, the 18:0 fatty acid increased at a low rate while thetrans fatty acid content increased at a much faster rate. The 16:0 and 18:0 content of the HMG was highest andtrans content the lowest during the period in which the triglyceride composition was the most diverse. The 54-carbon triglyceride content of the HMG increased from 64% to 78% during the two hours of hydrogenation. The short spacings for the HMG showed the presence ofβ crystals as well as several intermediate forms. The number of short-spacings increased with hydrogenation time. The differential scanning calorimetry (DSC) melting profile of the HMG showed one broad peak between 20 and 30°C and two peaks around 60°C and above. Crystallization temperatures of the HMG were in the range of 40–45°C. Presented at the 81st American Oil Chemists' Society Annual Meeting, April, 1990, Baltimore, Maryland.     

Characteristics of Oil from Hulless Barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.) Bran from Tibet

The bran of hulless barley (Hordeum vulgare L.) from Tibet was investigated. This paper reports on the physicochemical characteristics, lipid classes and fatty acids of the oil from the bran. The petroleum (60–90 °C) extract of hulless barley bran was found to be 8.1%. The investigated physiochemical parameters included density at 40 °C (0.96 g/cm³), refractive index at 40 °C (1.41), melting point (30.12 °C), acid value (11.6 mg KOH/g), peroxide value (19.41 μg/g), saponification value (337.62 mg KOH/g), iodine value (113.51 mg iodine/g) and unsaponifiable matter (4.5% of total lipids).The amount of neutral lipids in the crude oil was the highest (94.55% of total lipids), followed by glycolipids (4.20% of the total lipid) and phospholipids (1.25% of the total lipid). Linoleic acid (75.08% of total fatty acids) followed by palmitic acid (20.58% of total fatty acids), were the two major fatty acids in the oil. The results show that the oil from the hulless barley bran could be a good source of valuable essential fatty acids.     

The electrochemical hydrogenation of edible oils in a solid polymer electrolyte reactor. II. Hydrogenation selectivity studies

Soybean oil has been hydrogenated electrochemically in a solid polymer electrolyte (SPE) reactor at 60°C and 1 atm pressure. These experiments focused on identifying cathode designs and reactor operation conditions that improved fatty acid hydrogenation selectivities. Increasing oil mass transfer into and out of the Pd-black cathode catalyst layer (by increasing the porosity of the cathode carbon paper/cloth backing material, increasing the oil feed flow rate, and inserting a turbulence promoter into the oil feed flow channel) decreased the concentrations of stearic acid and linolenic acid in oil products [for example, an iodine value (IV) 98 oil contained 12.2% C_18:0 and 2.3% C_18:3]. When a second metal (Ni, Cd, Zn, Pb, Cr, Fe, Ag, Cu, or Co) was electrodeposited on a Pd-black powder cathode, substantial increases in the linolenate, linoleate, and oleate selectivities were observed. For example, a Pd/Co cathode was used to synthesize an IV 113 soybean oil with 5.3% stearic acid and 2.3% linolenic acid. The trans isomer content of soybean oil products was in the range of 6–9.5% (corresponding to specific isomerization indices of 0.15–0.40, depending on the product IV) and did not increase significantly for high fatty acid hydrogenation selectivity conditions.     

Effect of Different Frying Methods on the Total <Emphasis Type="Italic">trans</Emphasis> Fatty Acid Content and Oxidative Stability of Oils

The main objective of this study was to determine the effect of different frying oils and frying methods on the formation of trans fatty acids and the oxidative stability of oils. Sunflower, canola and commercial frying oils, the most commonly used oils for frying potatoes in the fast food industry, were used as the frying medium. The value for total polar compounds was highest when commercial frying oil was used in the microwave oven (22.5 ± 1.1). The peroxide value, as an indicator of oil oxidation, was lowest for microwave oven frying (2.53 ± 0.03). The K₂₃₂ and K₂₇₀ values were 0.41 ± 0.04 and 0.18 ± 0.02, respectively, for commercial frying oil in the microwave oven. The lowest free fatty acid content was recorded for the commercial frying oil used in the deep‐fat fryer at 190 °C. The highest iodine value was measured for sunflower oil used in the deep‐fat fryer (148.14 ± 0.07), indicating a greater degree of unsaturation. The lowest trans fatty acid value was recorded for sunflower oil in the microwave oven (0.17 ± 0.05), with a higher overall amount of total trans fatty acids observed for oils after frying in the electrical deep‐fat fryer compared to the microwave. Sunflower oil was favourable for both frying methods in terms of the trans fatty acid content.     

Preparative Separation of <Emphasis Type="Italic">cis</Emphasis>- and <Emphasis Type="Italic">trans</Emphasis>-Isomers of Unsaturated Fatty Acid Methyl Esters Contained in Edible Oils by Reversed-Phase High-Performance Liquid Chromatography

In order to measure exactly the trans-fatty acids content in food materials, a preparative group separation of cis- and trans-isomers of unsaturated fatty acid methyl esters (FAMEs) was achieved by an isocratic reversed-phase HPLC (RP-HPLC) method. The trans-isomers of 16:1, 18:1, 18:2, 18:3, 20:1 and 22:1 FAMEs were readily separated from the corresponding cis-isomers by a COSMOSIL Cholester C18 column (4.6 mm I.D. × 250 mm, Nacalai Tesque) or a TSKgel ODS-100Z column (4.6 mm I.D. × 250 mm, TOSOH), using acetonitrile as the mobile phase. This method was applied for determining the trans-18:1 fatty acid content in partially hydrogenated rapeseed oil. The methyl esters of cis- and trans-18:1 isomers of the oil were collected as two separate fractions by the developed RP-HPLC method. Each fraction was analyzed by gas chromatography (GC) for both qualitative and quantitative information on its positional isomers. By a combination of RP-HPLC and GC methods, a nearly complete separation of cis- and trans-18:1 positional isomers was achieved and the trans-18:1 fatty acid content was able to be evaluated more precisely than is possible by the direct GC method. The reproducibility of cis- and trans-18:1 isomers fractionated by the RP-HPLC method was better than 98%. These results suggested that the preparative RP-HPLC method developed in this study could be a powerful tool for trans-fatty acid analysis in edible oils and food products as an alternative to silver-ion chromatography.     

Analysis and Formation of <Emphasis Type="Italic">trans</Emphasis> Fatty Acids in Corn Oil During the Heating Process

Formation and composition of trans fatty acids (TFA) in corn oil during the frying process at different temperatures was investigated using an improved analytical gas chromatography (GC) method. At temperatures above 180 °C and heating times over 2 h there was a significantly increased TFA content, which increased further at higher temperatures. The amounts of trans C18:1 and trans C18:2 increased from 0.64 and 9.0 to 7.86 and 65.48 mg/g after heating at 260 °C for 12 h, while the total amount of TFA increased from 9.64 to 73.34 mg/g. However, the contents of linoleic acid and α-linolenic acid under the same conditions reduced from 460.3 and 7.4 to 209.8 and 1.8 mg/g, respectively. These results show that heating can significantly induce cis to trans isomerization of unsaturated triglycerides, particularly at high temperatures.     

Partial Hydrogenation of Soybean Oil with Minimal <Emphasis Type="Italic">Trans</Emphasis> Fat Production Using a Pt-Decorated Polymeric Membrane Reactor

Partial hydrogenation of vegetable oils is carried out to improve the chemical stability and raise the melting point to produce semi-solid products such as margarine. Trans fatty acids formed during traditional hydrogenation have come under intense scrutiny with regard to human health. Here we report partial hydrogenation of soybean oil using a high performance integral-asymmetric polyetherimide membrane sputtered with platinum to deliver hydrogen directly to or near the catalytic sites. Oil flows past the platinum-coated “skin” side of the membrane while dissolved molecular and some atomic hydrogen is supplied from the highly porous substructure of the membrane. The membrane has a high hydrogen flux but is essentially impermeable to soybean oil. Hydrogenation using our metal/polymer catalytic composite membrane produced oil with only 4 wt.% total trans fatty acids and 14.5 wt.% C18:0 saturates at IV of 95 while the conventional Pt/C slurry reactor produced more than 10 wt.% TFA and the same amount of C18:0 saturates under similar conditions of temperature and pressure. Our concept requires hydrogen pressures of only about 65 psi and temperatures near 70 °C. The polymeric base membranes used here have been mass produced and can be packaged in spiral wound modules. The relatively mild reaction conditions and the direct pathway to produce useful membrane modules combine to make our concept promising for near-term application.     

Low trans-Fat Spreads and Shortenings from a Catalyst-Switching Strategy

Low trans fatty acid basestocks suitable for blending with liquid oils to make spreads and shortenings are prepared by using a two-step hydrogenation process. The first step uses a nickel catalyst to hydrogenate soybean, canola, high-oleic sunflower, and high-oleic safflower oils to a predetermined iodine value. At this point in the reaction, the second step commenced. Addition of a platinum catalyst at 80 °C and 73 psi hydrogen pressure allowed for hydrogenation to proceed to iodine values of 40–50. These products had 11–18% trans fatty acid content. These were then blended with soybean oil (5–50% basestock) to give products with bulk properties similar to commercial spreads and shortenings but with about one third the levels of trans fat. Names are necessary to report factually an available data: the USDA neither guarantees nor warrants the standard of the product, and the use of the name USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Trans-free bakery shortenings from mango kernel and mahua fats by fractionation and blending

Bakery shortenings prepared by hydrogenation contain high levels of trans fatty acids, which are considered to be risk factors for cardiovascular disease. The shortenings prepared from maogo kernel and mahua fats have no trans fatty acids. Mahua fat was fractionated by dry fractionation to obtain a high-melting fraction (10% yield, Mh1). Mango fat was fractionated by two-stage solvent fractionation, separating about 15% high-melting fraction (Mk1) in the first stage, followed by 40% stearin (Mk2) in the second stage. The formulation containing 80% Mh1 and 20% of mango middle stearin fraction (Mk2) showed melting characteristics and onset and enthalpy of crystallization similar to those of commercial hydrogenated shortenings designed for cakes and biscuits. The formulation suitable for puff pastry shortening was prepared by blending 50% mango 1st stearin (Mk1) and 50% mahua fat with addition of 5–7% of fully hydrogenated vegetable oil. The formulations having melting characteristics similar to those of commercial cake and biscuit shortenings were also prepared by blending 40% mango fat and 60% mahua fat with 5–7% incorporation of fully hydrogenated peanut oil. However, these formulations showed delayed transition to the stable forms compared to those of commercial samples. Fatty acid composition revealed that commercial hydrogenated shortenings consisted of 18–29% trans oleic acid, whereas the formulations we prepared did not contain any trans acids. The iodine values of commercial samples were 57–58, whereas the value for the formulations prepared were 47–53. The consistency of the prepared samples as measured by cone penetrometer was slightly harder than commercial samples. These studies showed that it is possible to prepare bakery shortenings with no trans fatty acids by using mango and mahua fats and their fractions.     

Degradation and Nutritional Quality Changes of Oil During Frying

The changes in regular canola oil as affected by frying temperature were studied. French fries were fried intermittently in canola oil that was heated for 7 h daily over seven consecutive days. Thermo-oxidative alterations of the oil heated at 185 ± 5 or 215 ± 5 °C were measured by total polar components (TPC), anisidine value (AV), color components formation, and changes in fatty acid composition and tocopherols. Results showed that TPC, AV, color and trans fatty acid content increased significantly (P < 0.05) as a function of frying temperature and time. The oil polyunsaturated fatty acids (PUFA) decreased in direct proportion to frying temperature and time. After 7 days of frying, the amount of PUFA was reduced by half and the trans isomers contribution increased 2.5 times during frying at 215 °C. Of the parameters assessed, total polar component and color had the highest correlation, with correlation coefficients of 0.9650 and 0.9302 for frying at 215 and 185 °C, respectively. TPC formation correlated inversely with the reduction of tocopherols.     

Catalytic behavior of ruthenium in soybean oil hydrogenation

Soybean oil was hydrogenated with a carbon‐supported ruthenium catalyst (Ru/C) at 165 °C, 2 bar H₂ and 500 rpm stirring speed. Reaction rates, trans isomer formation, selectivity ratios and melting behaviors of the samples were monitored. No catalytic activity was found for the application of 10 ppm of the catalyst, and significant catalytic activity appeared at >50 ppm of active catalyst. The catalyst concentration had an effect on the reaction rate of hydrogenation, but the weight‐normalized reaction rate constant (k_c) was almost independent of the catalyst concentration at lower iodine values. Ru/C generated considerable amounts of trans fatty acids (TFA), including high amounts of trans 18:2, and also stearic acid, due to its very non‐selective nature. The selectivity ratios were found to be low and varied between 1.12 and 4.32 during the reactions. On the other hand, because of the low selectivity, higher slip melting points and solid fat contents at high temperatures were obtained than those for nickel and palladium catalysts. Another different characteristic of this catalyst was the formation (max 1.67%) of conjugated linoleic acid (CLA) during hydrogenation. Besides, CLA formation in the early stages of the reactions did not change very much with the lower iodine values.     

trans fatty acids. 4. Effects on fatty acid composition of colostrum and milk

trans Isometric fatty acids of partially hydrogenated fish oil (PHFO) consist oftrans 20∶1 andtrans 22∶1 in addition to thetrans isomers of 18∶1, which are abundant in hydrogenated vegetable oils, such as in partially hydrogenated soybean oil (PHSBO). The effects of dietarytrans fatty acids in PHFO and PHSBO on the fatty acid composition of milk were studied at 0 (colostrum) and 21 dayspostpartum in sows. The dietary fats were PHFO (28%trans), or PHSBO (36%trans) and lard. Sunflower seed oil (4%) was added to each diet. The fats were fed from three weeks of age throughout the lactation period of Experiment 1. In Experiment 2 PHFO or “fully” hydrogenated fish oil (HFO) (19%trans), in comparison with coconut oil (CF) (0%trans), was fed with two levels of dietary linoleic acid, 1 and 2.7% from conception throughout the lactation period. Feedingtrans-containing fats led to secretion oftrans fatty acids in the milk lipids. Levels oftrans 18∶1 andtrans 20∶1 in milk lipids, as percentages of totalcis+trans 18∶1 andcis+trans 20∶1, respectively, were about 60% of that of the dietary fats, with no significant differences between PHFO and PHSBO. The levels were similar for colostrum and milk. Feeding HFO gave relatively lesstrans 18∶1 andtrans 20∶1 fatty acids in milk lipids than did PHFO and PHSBO. Only low levels ofcis+trans 22∶1 were found in milk lipids. Feedingtrans-containing fat had no consistent effects on the level of polyenoic fatty acids but reduced the level of saturated fatty acids and increased the level ofcis+trans monoenoic fatty acids. Increasing the dietary level of linoleic acid had no effect on the secretion oftrans fatty acids but increased the level of linoleic acid in milk. The overall conclusion was that the effect of dietary fats containingtrans fatty acids on the fat content and the fatty acid composition of colostrum and milk in sows were moderate to minor.     

Chemical composition and physicochemical and hydrogenation characteristics of high-palmitic acid solin (low-linolenic acid flaxseed) oil

The physicochemical characteristics and FA compositions were determined for refined-bleached-deodorized (RBD) high-palmitic acid solin (HPS) oil, RBD solin oil, and degummed linseed oil. The predominant FA in HPS oil were palmitic (16.6%), palmitoleic (1.4%), stearic (2.5%), oleic (11.3%), linoleic (63.7%), and linolenic (3.4%). HPS oil was substantially higher in palmitic acid than either solin oil or linseed oil, and similar to solin oil in linolenic acid content. HPS, solin, and linseed oils exhibited similar sterol and tocopherol profiles. The physicochemical characteristics of the three oils (iodine value, saponification value, m.p., density, specific gravity, viscosity, PV, FFA content, color) reflected their FA profiles and degree of refinement. During hydrogenation of HPS oil, the proportion of saturated FA (palmitic and stearic) increased, and that of unsaturated FA (oleic, linoleic, and linolenic) decreased as the iodine value declined. This resulted in an inverse linear relationship between m.p. and iodine value. Hydrogenation also generated trans FA. The proportion of trans FA was inversely related to iodine value in partially hydrogenated samples. Fully hydrogenated HPS oil (i.e., HPS stearine, iodine value <5) was devoid of trans FA.     

Low-<Emphasis Type="Italic">trans</Emphasis> Shortening and Spread Fats Produced by Electrochemical Hydrogenation

Partially hydrogenated soybean oils (90–110 IV) were prepared by electrochemical hydrogenation at a palladium/cobalt or palladium/iron cathode, moderate temperature (70–90 °C) and atmospheric pressure. The trans fatty acid (TFA) contents of 90–110 IV products ranged from 6.4 to13.8% and the amounts of stearic acid ranged from 8.8 to 15.4% (the higher stearic acid contents indicated that some reaction selectivity had been lost). The solid fat values and melting point data indicated that electrochemical hydrogenation provides a route to low-trans spreads and baking shortenings. Shortenings produced by conventional hydrogenation contain 12–25% trans fatty acids and up to 37% saturates, whereas shortening fats produced electrochemically had reduced TFA and saturate content. Electrochemical hydrogenation is also a promising route to low-trans spread and liquid margarine oils. Compared to commercial margarine/spread oils containing 8–12% TFA, the use of electrochemical hydrogenation results in about 4% TFA. Names are necessary to report factually an available data: the USDA neither guarantees nor warrants the standard of the product, and the use of the name USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Physical and chemical properties of trans-free fats produced by chemical interesterification of vegetable oil blends

Fat blends, formulated by mixing a highly saturated fat (palm stearin or fully hydrogenated soybean oil) with a native vegetable oil (soybean oil) in different ratios from 10:90 to 75:25 (wt%), were subjected to chemical interesterification reactions on laboratory scale (0.2% sodium methoxide catalyst, time=90 min, temperature=90°C). Starting and interesterified blends were investigated for triglyceride composition, solid fat content, free fatty acid content, and trans fatty acid (TFA) levels. Obtained values were compared to those of low- and high-trans commercial food fats. The interesterified blends with 30–50% of hard stock had plasticity curves in the range of commercial shortenings and stick-type margarines, while interesterified blends with 20% hard stock were suitable for use in soft tubtype margarines. Confectionery fat basestocks could be prepared from interesterified fat blends with 40% palm stearin or 25% fully hydrogenated soybean oil. TFA levels of interesterified blends were low (0.1%) compared to 1.3–12.1% in commercial food fats. Presented at the 88th AOCS Annual Meeting and Expo, May 11–14, 1997, Seattle, Washington.     

Effects of hydrogenation parameters on trans isomer formation,selectivity and melting properties of fat

Effects of hydrogenation conditions (temperature, hydrogen pressure, stirring rate) on trans fatty acid formation, selectivity and melting behavior of fat were investigated. To this aim, soybean oil was hydrogenated under various conditions and fatty acid composition, trans isomer formation, slip melting point (SMP), solid fat content (SFC) and iodine number (IV) of the samples withdrawn at certain intervals of the reactions were monitored. A constant ratio (0.03%) of Nysosel 222 was used in the various combinations of temperature (150, 165 and 180 °C), stirring speed (500, 750 and 1000 rpm) and hydrogen pressure (1, 2 and 3 bar). Raising the temperature increased the formation of fatty acid isomers, whereas higher stirring rates decreased this formation, while changes in hydrogen pressure had no effect or slightly reduced it, depending on other parameters. Results also indicated that the trans fatty acid ratio increased with IV reduction, reached the highest value when the IV was about 70 and decreased at IV < 70 due to saturation. Selectivity values (S₂₁) at that point ranged between 5.78 and 11.59. Lower temperatures and higher stirring rates decreased not only the trans isomer content but also the S₂₁ values at significant levels. However, same effects were not observed with the changes in hydrogen pressure. It was determined that a high SMP does not necessarily mean a high SFC. Selective conditions produced samples with higher SFC but lower SMP, which is possibly because of higher trans isomer formation as well as lower saturation.     

<Emphasis Type="Italic">cis</Emphasis>-, <Emphasis Type="Italic">trans</Emphasis>- and Saturated Fatty Acids in Selected Hydrogenated and Refined Vegetable Oils in the Indian Market

The fatty acid composition of 27 samples of commercial hydrogenated vegetable oils and 23 samples of refined oils such as sunflower oil, rice bran oil, soybean oil and RBD palmolein marketed in India were analyzed. Total cis, trans unsaturated fatty acids (TFA) and saturated fatty acids (SFA) were determined. Out of the 27 hydrogenated fats, 11 % had TFA about 1 % where as 11 % had more than 5 % TFA with an average value of about 13.1 %. The 18:1 trans isomers, elaidic acid was the major trans contributor found to have an average value of about 10.8 % among the fats. The unsaturated fatty acids like cis-oleic acid, linoleic acid and α-linolenic acid were in the range of 21.8–40.2, 1.9–12.2, 0.0–0.7 % respectively. Out of the samples, eight fats had fatty acid profiles of low TFA (less than 10 %) and high polyunsaturated fatty acids (PUFA) such as linoleic and α-linolenic acid. They had a maximum TFA content of 7.3 % and PUFA of 11.7 %. Among the samples of refined oils, rice bran oil (5.8 %) and sunflower oil (4.4 %) had the maximum TFA content. RBD palmolein and rice bran oils had maximum saturated fatty acids content of 45.1 and 24.4 % respectively. RBD palmolein had a high monounsaturated fatty acids (MUFA) content of about 43.4 %, sunflower oil had a high linoleic acid content of about 56.1 % and soybean oil had a high α-linolenic acid content of about 5.3 %.     

Preparation and Evaluation of Biodiesel from <Emphasis Type="Italic">Sterculia foetida</Emphasis> Seed Oil

Sterculia foetida oil contains cyclopropene fatty acids namely 8,9-methylene-heptadec-8-enoic acid (malvalic) and 9,10-methylene-octadec-9-enoic acid (sterculic) to an extent of 50–55%. The present study reports the preparation of biodiesel from S. foetida oil using sodium hydroxide as catalyst. The resultant biodiesel was evaluated for physico-chemical properties namely iodine value (72.6), free fatty acids (0.17%), phosphorous content (0 ppm), flash point (179 °C), cloud point (3 °C), pour point (3 °C), viscosity at 40 °C (4.72 cSt), oxidative stability at 110 °C (3.42 h), density (0.850 g/cm³ at 15 °C), and trace metals (Group I metals 0.21 ppm). The properties were compared with that of sunflower, soybean and rapeseed oil-based biodiesels and found to be comparable except for the pour point.