Removal of copper from hydrogenated soybean oil

Hydrogenation with a copper-chromite catalyst at 170 C, 30 psi, increased the copper content of a refined, bleached soybean oil from 0.02 to as much as 3.8 ppm. Removing residual copper from soybean oil is essential to the successful use of copper catalysts for selective hydrogenation. Various methods were examined to remove this copper, including alkali refining, bleaching, acid washing, citric acid treatment and cation-exchange resin treatment. Properly conducted, each of the methods except alkali refining gives 95% or higher removal of copper introduced during hydrogenation. Ion exchange appears to be the most economical, but addition of about 0.01% citric acid during deodorization may be needed to inactivate traces of unremoved copper. Soybean oil hydrogenated with a copper-chromite catalyst, bleached or treated with an ion-exchange resin and deodorized with 0.01% citric acid added had low AOM peroxide values and acceptable flavor scores after eight days at 60 C which indicate that removal of residual copper from the oil should be adequate for the production of stable oils low in linolenic acid content. Presented at AOCS Meeting, Chicago, October 1967.     

Chemical and physical effects of processing fats and oils

Soybean oil is processed for a variety of food uses, salad/cooking oil, margarine and shortening. Crude soybean oil is composed mainly of triglycerides but also contains measurable amounts of minor constituents that may have beneficial or detrimental effects on oil characteristics. The nature of these minor constituents, the role they play in oil stability or deterioration and their fate during processing are subjects of this review. Iodine value, fatty acid composition, solid fat index and congeal point are chemical and physical characteristics of oil that are affected by the hydrogenation process. Techniques and effects of degumming, alkali refining, bleaching, hydrogenation, winterization and deodorization are discussed. Utilization or disposal of by-products or wastes from each processing step is reviewed. Presented at Northeast Section, AOCS, Symposium, Newark, N.J., November 5–6, 1979.     

Oxidative stability of high-fatty acid rice bran oil at different stages of refining

The contents of natural antioxidants and the oxidative stability of rice bran oils at different refining steps were determined. Tocopherols and oryzanols were constant in crude and degummed oils but decreased in alkali-refined, bleached and deodorized oils. The process of degumming, alkali-refining, bleaching and deodorization removed 34% of the tocopherols and 51% of the oryzanols. During storage of deodorized oil for 7 wk, 34% of the tocopherols and 19% of the oryzanols were lost. The maximum weight gain, peroxide value and anisidine value were obtained from alkali-refined oil during storage. The order of oxidation stability was crude ≥ degummed > bleached = deodorized > alkali-refined oil.     

Metals in soybean oil

Certain metals often produce deleterious effects when present in soybean oil. Trace quantities of copper, iron and manganese dramatically reduce the oxidative stability of edible oils. The presence of calcium and magnesium in crude oils reduces the efficiency of degumming and refining operations. Sodium soaps reduce bleaching efficiency by inactivating adsorption sites on bleaching earth. Phosphatides or phosphorous containing lipids exert a poisoning effect on hydrogenation catalysts. Nickel, an artifact of hydrogenation, must be removed from the oil for health, stability and safety considerations. This paper provides an overview of the various effects of metals on processing and stability, describes how to inhibit or diminish their activity, and discusses various analytical techniques for identification and quantitation of the metals present in soybean oil.     

Effects of processing steps on the contents of minor compounds and oxidation of soybean oil

The processes of degumming, alkali refining, bleaching and deodorization removed 99.8% phospholipids, 90.7% iron, 100% chlorophyll, 97.3% free fatty acids and 31.8% tocopherols from crude soybean oil. The correlation coefficient between the removals of phosphorus and iron in soybean oil during processing was r = 0.99. The relative ratios of α-, β -, γ- and δ-tocopherols in crude oil, degummed oil, refined oil, bleached oil and deodorized soybean oil were almost constant, γ- and δ -tocopherols represented more than 94% of tocopherols in soybean oil. The order of oxidation stability of oil is crude > deodorized > degummed > refined > bleached oil.     

Degumming,refining, bleaching,and deodorization theory

Basic theory and principles of degumming, refining, bleaching, and deodorization are reviewed. Composition of crude oils, hydration of ions and molecules, neutralization of organic acid, and separation and modification of products by centrifugation, adsorption, and vacuum steam distillation are briefly summarized. Reactions of vegetable oils include hydration, neutralization, and oxidation.     

Soybean oil: Update on number one

The growth and present stature of soybeans and soybean oil production and utilization in the world and in the USA is presented. Compositions of soybeans and soybean oil are compared with other common vegetable oils. The current and optimal processing practices of extraction, degumming, neutralization (caustic and physical), hydrogenation, and deodorization are discussed. Where appropriate, new and innovative approaches are introduced. Utilization of soybean oil is covered, followed by a historical and present view on the subject of soybean oil flavor and present and future nutritional considerations of soybean oil.     

Effect of processing on the composition and oxidative stability of coconut oil

The effect of various processing procedures on the composition and oxidative stability of coconut oil has been studied. The crude oil is relatively stable but major reductions in oxidative stability occur during the bleaching of oil degummed with phosphoric acid; during alkali refining; during the deodorization of oil degummed with citric acid and bleached; and during the deodorization of oil processed with a combined phosphoric acid degumming and bleaching operation. The reasons for the loss of oxidative stability during processing are discussed with reference to changes in the composition of the oil. Residual traces of citric acid or phosphoric acid play an important role in stabilizing processed oils. The tocopherol content is also important, although no additional stabilization of the oil occurs on adding levels of tocopherol above those present naturally in the crude oil. A combined phosphoric acid degumming and bleaching process leads to smaller losses of tocopherols than sequential treatments.     

Degumming and bleaching ofLesquerella fendleri seed oil

A lesquerella species (Lesquerella fendleri) being investigated as a domestic source of seed oil containing hydroxy fatty acids shows good agronomic properties and is being tested in semi-commercial production.Lesquerella fendleri seeds contain 25% oil, of which 55% is lesquerolic acid (14-hydroxy-cis-11-eicosenoic). Oils produced in pilot-plant quantities by screw press, prepress-solvent extraction and extrusion-solvent extraction processes have been refined in the laboratory by filtering, degumming and bleaching. Two American Oil Chemists’ Society (AOCS) standard bleaching earths and two commercial earths were compared for effectiveness in bleaching these dark, yellow-red, crude lesquerella oils. Free fatty acids (1.3%), iodine value (111), peroxide value (<4 meq/kg), unsaponifiables (1.7%) and hydroxyl value (100) were not significantly affected by degumming and bleaching, but phosphorus levels of 8–85 ppm in the crude oils were reduced to 0.5–1.1 ppm in the degummed and bleached oils. Crude oils had Gardner colors of 14, which were reduced to Gardner 9–11 in the degummed and bleached oil, depending on bleach type and quantity used. AOCS colors in the range of 21–25R 68–71Y were obtained. By including charcoal in the bleaching step, a considerably lighter oil could be obtained (Gardner 7).     

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.     

Continuous ultrasonic hydrogenation of soybean oil. II. Operating conditions and oil quality

In previous work we found that ultrasonic energy greatly enhanced the rate of hydrogenation of soybean oil. We have now investigated parameters of ultrasonic hydrogenation and the quality of the resulting products. Refined and bleached soybean oil was hydrogenated continuously with and without ultrasonic energy at different temperatures, pressures and catalyst concentrations. Flavor and oxidative stability of the oils were compared with a commercially hydrogenated soybean oil. The extent of hydrogenation (ΔIV) was not affected by temperature between 245 and 290 C, but was greater at 106 psig than at 65 psig hydrogen pressure. The ΔIV of hydrogenated oils increased linearly with catalyst concentration from 40 ppm to 150 ppm nickel. At the same catalyst concentration the IV drop was significantly increased when ultrasonic energy was used. By reducing the amount of power supplied to the ultrasonic reactor to 40% of full power, the specific power (watts/ΔIV) was lowered by 60%. Linolenate selectivities and specific isomerization (%trans/ΔIV) remained the same, but linoleate selectivities were lower than for batch hydrogenation under varied operating parameters. Flavor scores were not significantly different, initially or after storage eight days at 60 C, for oils continuously hydrogenated with and without ultrasonic energy. Hydrogenation of soybean oil with ultrasonic energy offers a method to produce good quality products at potentially lower cost than present methods.     

Effects of refining and bleaching on oxidative stability of sunflowerseed oil

Sunflowerseed oils extracted from seed grown in the northern and southern US were laboratory refined and bleached with 1 and 3% activated clay. The crude, refined, and bleached oils were heated for four 8-hr days. Samples of oil were taken daily and active oxygen method values determined. In addition, “Ple-zrs,” a porous, fat free snack item, were fried in the oils at the end of each day and stored for 5 weeks. Plots of the log of the active oxygen method values versus the number of hr the oil had been heated were straight lines, the slope of which reflected the oxidative stability of the oil on heating. The lack of change in slopes for the southern oils indicated that oxidative stability after heating was not changed markedly by refining or bleaching. Two samples of northern oil, the refined and oil bleached with 1% activated clay, showed an increase in oxidative stability on heating but a lowering of overall stability. The peroxide values of the oils expressed from the stored “Ple-zrs” indicated that the southern oil was slower than the northern oil to oxidize on storage in a fried product.     

The total degumming process

A novel degumming process is described that is applicable to both undegummed and water-degummed oils. Such totally degummed oils have residual iron contents below 0.2 ppm Fe and residual phosphorus contents that average below 5 ppm P. Therefore, they can be physically refined to yield a stable refined oil while using the same level of bleaching earth commonly used for alkali refined oils prior to deodorization. They can also be alkali refined with reduced oil loss to yield a soapstock that only requires slight acidification for fatty acid recovery, and thus avoids the strongly polluting soap splitting process. The total degumming process involes dispersing a non-toxic acid such as phosphoric acid or citric acid into the oil, allowing a contact time, and then mixing a base such as caustic soda or sodium silicate into the acid-in-oil emulsion. This keeps the degree of neutralization low enough to avoid forming soaps, because that would lead to increased oil loss. Subsequently, the oil is passed to a centrifugal separator where most of the gums are removed from the oil stream to yield a gum phase with minimal oil content. The oil stream is then passed to a second centrifugal separator to remove all remaining gums to yield a dilute gum phase which is recycled. Washing and drying or in-line alkali refining complete the process. After the adoption of the total degumming process, in comparison with the classical alkali refining process, an overall yield improvement of approximately 0.5% has been realized. It did not matter whether the totally degummed oil was subsequently alkali refined, bleached and deodorized, or bleached and physically refined.     

Distributions of Polycyclic Aromatic Hydrocarbons and Phthalic Acid Esters in Gums and Soapstocks Obtained from Soybean Oil Refinery

Soybean oil gums and soapstocks are important by-products that may potentially be contaminated by persistent organic pollutants (POP) such as polycyclic aromatic hydrocarbons (PAH) and phthalic acid esters (PAE), thus lowering the value when using them as starting materials to produce animal feed additives, food industry ingredients, and pharmaceutical products. In the present work, PAH and PAE distributions in these two types of by-products were detected using solvent extraction–solid phase extraction purification coupled with gas chromatography–mass spectrometry. Total PAH and PAE amounts in the soapstocks were significantly higher than those in the gums, thus indicating that neutralization showed much higher removal efficiency than degumming in terms of PAH and PAE eliminations. Meanwhile, the results proved that the concentrations of these two kinds of contaminants in the soybean oil gums and soapstocks were much higher than those in the soybean oils, suggesting that further investigations were needed and that the contents of PAH and PAE in soybean oil refining by-products should be carefully monitored and regulated.     

The Total Degumming Process – Theory and Industrial Application in Refining and Hydrogenation

The degumming of vegetable oils prior to physical refining is a crucial preliminary step. The degumming process is not only largely responsible for the quality of the final product, but it also determines the amount of bleaching earth to be used, which has a substantial effect on the yield improvement which can be attained by this route. Investigations show clearly that iron, as a pro-oxidant, strongly influences the stability of refined oils, and that oil, degummed before bleaching and physical refining, may contain a maximum of 0.2 ppm Fe, if it is to yield a stable product. The Total Degumming Process has been developed on the basis of these findings, to make it possible to degum oil to a residual Fe-level below 0.2 ppm and a residual phosphorus content below 10 ppm. The principles and industrial application of the process have been considered. The results of industrial production using different raw materials of various qualities have been used to make a comparison between the conventional refining process (neutralization – bleaching – deodorization) and the Total Degumming Process in combination with physical refining. The combination of the Total Degumming Process and a simplified caustic refining process, and the use of Totally Degummed Oil for hydrogenation have also been considered.     

Zu den Veränderungen von Rapsöl und Leinöl während der Verarbeitung

Changes of rapeseed and linseed oil during processing During processing of crude oil in a large oil mill, three samples each of rapeseed and linseed were investigated at each processing stage, i.e. press oil, solvent-extracted oil, mixed oil, and degummed/caustic refined oil. In the case of rapeseed also bleached and desodorized oils (230°C; 3.0 mbar for 2 h) were investigated. Rapeseed and linseed oil showing the typical major fatty acids contained less than 1% trans-isomeric fatty acids (trans fatty acids = TFA). Linseed oil had a similar TFA-concentration as rapeseed oil, and the concentrations did not change during the processing stages up to degummed/caustic refined oil, and were also unchanged in the bleached rapeseed oil. Desodorization of rapeseed oil, however, trebled the TFA concentration to 0.58%. The detected tocopherol patterns were typical of rapeseed and linseed oils. There was no difference between mixed oil and degummed/caustic refined oil in the total concentration of tocopherols. Neither had bleaching any effect. Rapeseed oil desodorization diminished total tocopherol concentration by 12% from 740 mg/kg to 650 mg/kg. Due to degumming/caustic refining the phosphorus concentration of both oils decreased to less than a tenth compared to mixed oil. Other elements determined in degummed/caustic refined rapeseed oil were not detectable (manganese < 0.02 mg/kg, iron < 0.4 mg/kg, copper < 0.02 mg/kg, lead < 10 μg/kg) or only as traces zink 0.1 mg/kg, cadmium 2 μg/kg). In linseed oil, which initially showed a higher trace compounds concentration, a significant decrease was found by degumming/caustic refining. Iron could not be detected. There were traces of zinc, manganese, copper, lead, and cadmium. There was no difference between the acid values of rapeseed and linseed crude oil. Acid value decreased drastically already during the degumming/caustic refining stage. The crude linseed oils had a higher peroxide value, anisidine value and diene value than the corresponding crude rapeseed oils. With peroxide values of ≤ 0.1 mEq O₂/kg found in almost all investigated rapeseed oils, no effect of refining could be detected. The anisidine value showed an increase after bleaching. Desodorization trebled the diene value.     

Quality of oil from damaged soybeans

Various processing steps were explored in an at-tempt to improve the quality of oil from field- and storage-damaged soybeans. A crude soybean oil (5.7% free fatty acid) commercially extracted from damaged soybeans was degummed in the laboratory with different reagents: water, phosphoric acid, and acetic anhydride. Two alkali strengths, each at 0.1 and 0.5% excess, were used to refine each degummed oil. After vacuum bleaching (0.5% activated earth) and deodorization (210 C, 3 hr), these oils were un-acceptable as salad oils. A flavor score of 6.0 or higher characterizes a satisfactory oil. Scores of water and phosphoric acid degummed oils ranged from 4.5 to 5.1, while acetic anhydride degummed oils aver-aged 5.6. Flavor evaluations of (phosphoric acid de-gummed) single- and double-refined oils (210 C deodorization) showed that the latter were signifi-cantly better. Flavor scores increased from 5.0 to about 6.0. To study the effects of deodorization tem-perature, the crude commercial oil was alkali-refined, water-washed and bleached with 0.5% activated earth, but the degumming step was omitted. Flavor evalua-tion of oil deodorized at 210, 230, and 260 C showed that each temperature increment raised flavor scores significantly. Further evaluations of specially proc-essed oils (water, phosphoric acid, and acetic anhy-dride degummed oils given single and double refinings and deodorized at 260 C) showed that deodorization temperature is the most important factor affecting the initial quality of oil from damaged beans. Flavor evaluations showed that hydrogenation and hydro-genation-winterization treatments produced oils of high initial quality, but with poorer keeping proper-ties than oils from normal beans. No evidence was found implicating nonhydratable phosphatides in the oil flavor problem. Iron had a deleterious effect in oils not treated with citric acid during deodorization. Presented at AOCS Meeting, Philadelphia, September 1974.     

50 Jahre Technologie pflanzlicher Öle und Fette - ein Erfahrungsbericht

50 Years Technology of Vegetable Oils and Fats - a Report of Experiences In a survey about the development of the technology of vegetable oils and fats between 1932 and 1982 above all those areas are dealt, in which the author could contribute to the optimization of technological process steps and to the quality improvement of final products. It is described in detail: influence of solvent composition on benzine losts and on hydrocarbon retention in the oil seed extraction, improvement of the lecithin removal process, the entire desliming of extracted oils and its influence on raffinate quality, methods for determination of refining lost and for estimation of quality of raw and refined oils, comparison between various alkali-neutralization methods, relations between bleaching earth activity and oxidation stability of the oils, recovery of oil from used bleaching earth, distillative neutralization and determination of optimal deodorising conditions. The report is finished with hints on the importance of special fats for the fat processing industry obtained by hydrogenation, interesterification or fractionation.     

Effect of phospholipid structure on kinetics and chemistry of soybean oil hydrogenation with nickel catalysts

Phospholipids (PL) are one of the compounds which poison nickel catalysts during the hydrogenation process. It was affirmed that even trace amounts of PL (5—10 ppm P) cause a decrease in catalyst activity. Quantities over 50 ppm P almost totally inhibit the reaction. In bleached oils used for hydrogenation, PL exist as native compounds as well as products of their transformation. In the present work, the effect of native phospholipids, lysophospholipids (LPL) and phosphatidic acids (PA) on the kinetics and chemistry of soybean oil hydrogenation was investigated. It was found that PA were more toxic to nickel catalysts than LPL and native PL. Fine‐grained catalyst was more active and resistant to the poisoning effect of phospholipids than moderate‐grained catalyst. No changes in the oil hydrogenation chemistry were observed in the presence or absence of PL; thus, linoleic and linolenic selectivity and specific isomerization did not undergo any change.     

Adsorptive bleaching of soybean oil with non-montmorillonite Zambian clays

As an alternative to montmorillonite clay, three local Zambian clays have been used to bleach soybean oil. The bleaching action of the natural clays was poor when compared with commercial acid-activated montmorillonite (M-C) and activated charcoal (A-C) adsorbents. However, acid-activation of the Zambian clays profoundly increased their adsorptive activity. Reduction of 88% in soybean oil color (Lovibond Red) by each of the three activated Zambian clay samples represented an efficiency close to that of montmorillonite (94%) and better than activated charcoal (63%). Peroxide value (PV) of the oil was reduced by 85% (M-C) and 78% (A-C) while 68% was the highest reduction for the activated Zambian clays. After 12 wk of storage at ambient temperature, the bleached soybean oil samples showed some oxidation. Consideration of the totox values indicated that the Zambian clay-bleached oil was more stable over this length of storage when compared with the M-C bleached oil. The bleaching action shown by aluminum-exchanged clays was closely related to their acid-activated counterparts. These results demonstrate a dependency of adsorptive bleaching with Zambian clays on proton availability. Comparative powder x-ray diffraction analysis of the clays showed that quartz was the major mineral present, followed by kaolinite. No montmorillonite was detected. It was concluded that by appropriate treatment to generate Brönsted acidity (protons), Zambian clays can be converted into potent adsorbents for soybean oil impurities.