Behavior of DDT,polychlorinated biphenyls (PCBs), and dieldrin at various stages of refining of marine oils for edible use

Two 300-lb batches of Eastern Canadian herring (Clupea harengus) oil were subjected to pilot plant processing to margarine stock for edible use. Samples were taken at various stages during processing for analysis of residues of the insecticide DDT and its metabolites DDD and DDE, of polychlorinated biphenyls (PCBs) and of dieldrin. Residue concentrations in the oil were not affected by degumming (phosphoric acid wash), alkali refining, or bleaching with activated earth. DDT and dieldrin were readily and completely destroyed by commercial hydrogenation over Ni catalyst, and DDD was largely removed at the same time. DDE and PCBs were partially reduced during hydrogenation in the one run in which DDD was completely removed, but were unaffected in another run, in which DDD was only partially removed. Deodorization of the oil with steam and vacuum effectively removed those residues which survived hydrogenation. Analysis of the Ni catalyst before and after hydrogenation showed that removal of residues during hydrogenation was not due to their adsorption to the catalyst, but was more probably due to metal-catalyzed degradation to unidentified products. Deodorizer condensates showed only a slight enrichment in residue levels over those found in the oil.     

Physical refining of edible oils

Crude oils obtained by oilseed processing have to be refined before the consumption in order to remove undesirable accompanying substances. The traditional alkali refining is often replaced by physical refining in which the use of chemicals is reduced. The most widely used method is steam refining. The crude oil quality is very important in order to obtain high quality refined oil. Furthermore, the oil should be efficiently degummed to remove phospholipids as well as heavy metals and bleached to remove pigments. The most important step consists of the application of superheated steam under low pressure and at temperatures higher than 220 °C. Both free fatty acids and objectionable volatiles, formed by cleavage of lipid oxidation products, are removed. A disadvantage is the partial loss of tocopherols. Side reactions, particularly isomerization of polyunsaturated fatty acids, should be minimized. The quality of physically refined oil is close to that of alkali refined oils, but losses of neutral oil are lower and the environment is less polluted. Among other methods of physical refining the application of selective membranes is promising.     

Reactors for hydrogenation of edible oils

Due to the characteristics of the hydrogenation of edible oil, by far the most common type of reactor has been the batch-type shurry hardener. Although continuous reactors offer several advantages compared to batch reactors, they are seldom used in the industry. This review paper describes the most commonly used full-scale reactors, both batch and continuous. Several different laboratory reactors are also described. The experimental results obtained from those reactors indicate that it is possible to achieve selectivites and reaction rates in a continuous reactor as high as in a slurry batch reactor.     

Clay-heat refining of edible oils

The treatment of crude edible oils with sodium hydroxide solutions is the standard refining procedure in the industry. Refining with NaOH removes free fatty acids, some phosphatides, proteinaceous matter and some colored material. Up to now experience has shown that most oils cannot be deodorized satisfactorily unless they have been caustic-refined. In the past, when most crude oils contained several per cent of free fatty acids, caustic-refining offered itself as a particularly suitable means of preparation for further processing. In recent years the free fatty acid content of crude oils has been, in most cases, only a fraction of 1%, which could very readily be removed in the process of deodorization. A prerequisite for this would be to remove by some other means those substances that interfere with satisfactory deodorizing. It has been found that the process of bleaching can be used for this purpose if the oil is pretreated with 0.1–0.5% phosphoric acid and bleached at 325–350 F. The amount of bleaching clay required depends on the type of oil and its quality, but with many oils up to 2% clay is satisfactory. The amount of phosphoric acid necessary also depends on the type of oil. One of nine papers presented in the symposium “Processing of Edible Oils,” AOCS Meeting, Ottawa, September 1972.     

Physical refining of edible oils

Physical refining of edible oils offers several advantages over alkali refining. The method described for physical refining of rapeseed oil involves several novel factors, including the availability of cold-pressed rapeseed oil low in phosphatide content and deacidification/deodorization in a film molecular evaporator. Parameters are presented from a pilot plant unit with an output of 500 metric tons per year. Further applications of the technology are proposed, including the processing of oils to pharmaceutical-grade products.     

Pretreatment of edible oils for physical refining

Physical refining of edible oils is briefly reviewed. Recent developments regarding the pretreatment of oils and fats are described in detail and methods are critically evaluated with special emphasis on their effectiveness in removing undesired minor components, their cost of operation and their effect on the environment.     

New integrated refining process for edible oils

Summary Dust-free solvent meal can be produced by pretreating meats with granular soda ash prior to oil extraction, addition of foots from miscella-refining operation to meal, and screening meal from dryers prior to grinding, then grinding only overs and blending with screened meal. By exclusion of air and light and by properly coordinating the miscella refining procedure, light-colored, soap-free oil can be produced, using low Baumé lye. Refined miscella can be winterized in a short enough time to warrant doing it in a continuous plant, giving yields and chill tests comparable to or better than conventionally winterized oil. A continuous deodorizer followed by continuous injection of nitrogen into the deodorized, cooled salad oil protects the oil from oxidation in this integrated, continuous salad-oil plant. Presented before the Spring Meeting of the American Oil Chemists’ Society in Houston, Tex., April 22–25, 1956.     

Behavior of N-methylcarbamate pesticides during refinement processing of edible oils

The following N-methylcarbamate pesticides, aldicarb, aldicarb sulfoxide, aldicarb sulfone, oxamyl, methomyl, thiodicarb, propoxur, carbofuran, carbosulfan, benfuracarb, bendiocarb, carbaryl, fenobcarb and furathiocarb, were added to soybean oil, each at 5 mg/kg(5 ppm), followed by degumming, alkali refining, bleaching and deodorization for oil refinement. Residual pesticide content in each case was determined immediately after refining. DEGUMMING: Aldicarb, aldicarb sulfoxide, aldicarb sulfone, oxamyl, thiodicarb, carbosulfan, benfuracarb were each found to decrease by as much as 70% by H(3)PO(4) treatment, this being less than 26% noted for the other pesticides. With hot water treatment, the decrease in any one pesticide was less than 52%. ALKALI REFINING: The rate of decrease varied with the pesticide, ranging from 8% to 100%. 200%NaOH were effectively brought about pesticide removal, compared to 125%NaOH. BLEACHING: Aldicarb, aldicarb sulfoxide, aldicarb sulfone, oxamyl, methomyl, thiodicarb, carbosulfan, benfuracarb, bendiocarb and furathiocarb each decreased by more than 80% with activated clay containing activated charcoal. Carbaryl decreased remarkably by this clay. Pesticide removal in all cases was at less than 30%. DEODORIZATION: 40% Furathiocarb, 14% carbosulfan, 11% benfuracarb and 3% carbofuran could still be detected subsequent to deodorization at 260 degrees C while all other pesticide amounts were too small to permit quantitative detection. Degumming with H(3)PO(4) and bleaching with activated clay caused the conversion of carbosulfan and benfuracarb into carbofuran. Carbofuran and furathiocarb may thus possibly still remain in the oil following the above 4 refinement processes.     

Low trans hydrogenation of edible oils

Hydrogenation of edible oils is an important process in the food industry to produce fats and oils with desirable melting properties and an improved shelf life. However, beside the desired hydrogenation reaction trans fatty acids are formed as well. As several studies indicate a negative health effect of trans fatty acids, consumer demands will urge the food producers to lower the content of trans fatty acids in their products. This article describes the option to reduce the trans levels in the hydrogenation of an edible oil by changing process conditions and by applying alternative low trans heterogeneous catalysts.     

A second-order model for catalytic-transfer hydrogenation of edible oils

A second-order kinetic model for hydrogenation of fatty acids in series has been developed and analyzed. The model is applied to the data obtained for sodium formatecatalyzed hydrogenation of soybean, peanut, corn, and olive oils. There is good agreement between the experimental data and predicted values obtained from the model as evidenced by the analysis of r ² and F-test values. The effect of individual fatty acid composition of various edible oils on the rate of hydrogenation has been explained in view of the mathematical model developed. The individual rate constants seem to obey the Arrhenius rate law. The second-order kinetic analysis discussed is found to be suitable for mathematically describing hydrogenation of vegetable oils by hydrogen donors as compared to the traditional first-order kinetic analysis     

Modification of a procedure for analytical hydrogenation of edible oils

Unsaturation, an important parameter in edible oils, can be determined by analytical hydrogenation. Recently Brown et al. (3–9) have proposed an “automatic” direct titration method for hydrogenation of various unsaturated organic compounds. Sodium borohydride, introduced through a pressure-actuated mercury valve, was utilized as hydrogen producing reagent, and both the hydrogen and the platinum catalyst were generated in situ. Application of the above method to determination of unsaturation in various edible oils was the subject of the present study. Several shortcomings inherent in the original procedure and apparatus have been overcome by introducing suitable changes. Isopropanol was used as a solvent for the borohydride; the buret was used at the operational stage in the near horizontal position; the end point manometer was filled with Brodie’s solution; and the system was preliminarily flushed with hydrogen from an external source and was operated at a slight overpressure. As a result of those changes, the determined hydrogen iodine values were closer to the expected ones and the standard deviations were appreciably lowered. Gravimetric determinations have confirmed Brown’s observation that the precipitated powder produced by reduction of chloroplatinic acid consists only of pure platinum. Microscopic examinations revealed that a finer structure and better dispersion is obtained when platinum was precipitated on activated carbon as support. This can be conceived with the observed higher over-all reaction rates achieved with the supported catalyst. Presented at the AOCS-ISF World Congress, Chicago, September 1970.     

Deacidification and recovery of distillates in the physical refining of edible oils

A pilot plant‐scale continuous deodorization installation was developed to simultaneously test several technological changes in the classical deodorization process: use of nitrogen as stripping gas, heating of the gas above the liquid oil, and use of shell‐and‐tube condensers for the recovery of distillates. Deacidification trials were first carried out on mixtures of commercial refined sunflower oil and high‐oleic distillates, and subsequently on bleached olive and sunflower oils. The performance of usual working conditions was analyzed: nitrogen mass flow rate, oil temperature and oil mass flow rate. Marked differences were not observed in the results of the final acidity, compositions of free fatty acids and sterols in the deacidified oil. However, the use of shell‐and‐tube condensers makes it possible to recover liquid distillates in better conditions than in the classical process for their further concentration, while at the same time reducing process pollution.     

Supercritical fluid processing of fish oils: Extraction of polychlorinated biphenyls

Polychlorinated biphenyls can be extracted from fish oils with supercritical carbon dioxide at quite modest temperature and pressure with little yield loss of the fish oils. The distribution coefficient, viz, the ratio of the concentration of polychlorinated biphenyls in the carbon dioxide and fish oil phases, respectively, was measured to be about 0.01 (wt basis). The selectivity of carbon dioxide for polychlorinated biphenyls was found to be very high, about 13 at a concentration of about 10 ppm.     

Catalytic behavior of palladium in the hydrogenation of edible oils

Palladium supported on alumina was used to hydrogenate soybean and canola oil. Previous literature reports indicated that palladium forms moretrans isomers than nickel. At 750 psig, 50 ppm palladium, and at 70 C, only 9.4%trans were formed when canola oil was hydrogenated to IV 74. In general, high pressure and low temperature favored lowtrans formation with no appreciable loss in catalyst activity. The effect of pressure, temperature and catalyst concentration on reaction rate,trans formation and selectivity is presented. A survey of various catalyst supports is discussed. Apparent activation energies of 6.3 to 8.9 kcal/mol were obtained; they are in good agreement with values reported in the literature.     

The fatty acid composition of edible marine fish oils

The body oils of 13 species of marine edible fishes found around the Karachi-Makran coast were studied by gas-liquid chromatography (GLC) for their fatty acid composition. The analyses showed the presence of fatty acids with chain lengths from 10 to 24 carbon atoms and with zero to six double bonds. The oils were found to be rich in polyunsaturated acids, particularly the penta- and hexaenoic. Certain major fatty acids were found to vary widely among the species: myristic acid 2.3 to 13.7%; palmitic 11.6 to 41.2%; stearich 7.2 to 23.2%; oleic 6.9 to 29.6%; eicosapentaenoic 1.4 to 19.0%; docosapentaenoic zero to 10.2%; and docosahexaenoic zero to 36.4%. The linoleic and linolenic acids were present in small amounts in some of the fish oils, and arachidonic acid was present in all of them.     

Automated refractive index measurement of catalyst-laden edible oils undergoing partial hydrogenation

A planar optical waveguide, excited by monochromatic light, becomes a sensor for measuring the refractive index (RI) of edible oils. RI is commonly used to determine iodine value (IV). This process sensor operates in the presence of nickel catalyst and diatomaceous earth (DE) powders. An on-line refractometer system, incorporating this sensor, demonstrates an accuracy of ±0.0001 RI units (RIU). Resolution is 0.00001 RIU. The waveguide refractometer is based on a loss in light transmission due to a temperature-induced matching of waveguide and oil RIs. An algorithm adjusts the RI to conform to the temperature and wavelength as specified in AOCS Method Cc 7-25 (Official Methods and Recommended Practices of the American Oil Chemists' Society, edited by D. Firestone, American Oil Chemists' Society, Champaign, 1989), the accepted procedure for RI measurement with an Abbé refractometer. The theory, construction and performance characteristics of a prototype waveguide refractometer are described. Samples of partially hydrogenated soybean oils (IV ranges=106–75) are first examined with the Abbé refractometer, then tested in the prototype waveguide refractometer. Catalyst and DE are subsequently added to each sample, and RI data are taken again with the waveguide refractometer. Results confirm the instrument's ±0.0001 RIU accuracy and its immunity to interference from catalyst and DE. Real-time operation holds promise for automatic control, improved production efficiency, and better batch-to-batch consistency of the hydrogenation process.