Industrial experiences of electric filtration in vegetable oil technology

Electric filtration is used to remove bleaching earth and other electrically charged particles from vegetable oils and fats. The grain size of bleaching earth does not significantly influence its separation during application of electric filtration. Therefore, it will be possible to separate bleaching earth with very small grains and increased capability for adsorption. The generation of an electrical field in an insulating fluid is the physical basis of the electric filtration, and under these conditions the generated Coulomb-power moves the bleaching earth grains to one of the electrodes where they will be separated. Electric filtration is available for industrial use. A modular unit enables the testing of all industrial applications directly in the refinery, and it permits the fulfilment of the requirements for the integration of an ÖHMI filtration^® unit in the whole process. Tests on a laboratory and a pilot plant scale have supplied the basis for smooth running of the first industrial plant installed in a large German edible oil refinery. Compact electric filtration plants enable a bleaching earth filtration largely independent of the grain size of the bleaching earth; they reduce the consumption of electric power, they can be adapted to each capacity due to the construction principal of the filter cell moduls, they decrease all expenditure of cleaning and the wear of the filter elements and clothes compared to the conventional cake filtration.     

Der gegenwärtige Stand der Bleichung im Raffinationsprozeß pflanzlicher Öle und tierischer Fette

The Present State of Bleaching in the Refining Process of Vegetable Oils and Animal Fats In the last decade the application of bleaching earth in the refining process of vegetable oils and fats has changed. Because of improved procedures of oil winning of oil seeds and increasing application of the distillative neutralization the emphasis of the application of bleaching earth is permanently lower appointed to the effect of decoloration. The removal of chlorophyll and redisual impurities (sleaming substances, soaps etc.) requires the application of bleaching earth. Some examples shall demonstrate the efficiency of various bleaching earths for removal of corresponding impurities from vegetable oils and fats.     

Einfluß der Struktur und der Morphologie von Bleicherden auf die Bleichwirkung bei Ölen und Fetten

Influence of the Structure and Morphology of Bleaching Earths on Their Bleaching Action on Oils and Fats In the manufacture of highly active bleaching earths from bentonite, the acid activation causes alterations in the chemical composition and structural as well as morphological properties of bentonite, depending on the concentration of acid, temperature, time etc. This has been demonstrated by changes in specific surface, volume of the micropores, particle size distribution and proportion of soluble silicic acid, and the impact of these alterations on the bleaching of vegetable oils is discussed. The results are supported by electron optical and X-ray investigations. Studies on repeated removal of silicic acid formed by acid treatment of bentonite as well as repeated acid activation indicate that the bleaching action of these earths depends not only on specific surface, but also, to a considerable extent, on the volume of micropores.     

Einfluß der Bleicherde auf die Fettsäurebildung während der Bleichung

Effect of Bleaching Earth on the Formation of Fatty Acids during Bleaching Investigations were carried out with neutralized soybean and cottonseed oils in order to determine the effect of acid content of bleaching earths with different activities on the formation of free fatty acids during the adsorptive bleaching. The free fatty acid content of the oils under investigation decreased with increasing acidity of the highly active and moderately active bleaching earth. The increase in acid value of the oil during bleaching is essentially dependent on the duration of bleaching and amount of bleaching earth employed. The water content of the oil has no decisive effect.     

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.     

What to Do with Spent Bleaching Earth? A Review

Animal fats and cold-pressed vegetable oils hardly need bleaching but when vegetable oils started to be produced by solvent extraction, the resulting oils were too dark to sell as such. That also holds for palm oil. Bleaching these oils with bleaching clay solved their color problems but led to the problem of spent earth disposal. Many ways of treating spent earth and ways of disposal have been suggested and/or developed in the past. They will be reviewed in this paper. Given the recent observation that slurrying spent bleaching earth with crude oil inhibits the deterioration of the residual oil in the earth, leads to the conclusion that, for an integrated oil mill-cum-refinery, the best way of spent bleaching earth disposal is the recycling of the earth to the solvent extractor, whereas stand-alone refineries are advised to sell their spent earth to chicken feed manufacturers. In future, a high-temperature hydrolysis process that can treat all kinds of fatty waste may become an attractive means of disposal as well.     

Der Futterwert von Fetten und Ölen aus Verarbeitungsprozessen bei Geflügel

Feeding Value of Fats and Oils from Finishing Processes for Poultry Altogether two trials with 22 different fats/oils have been carried out. In the first trial the interesterification and the digestibility of the fatty acids of seven fats and oils from the finishing processes with different contents of polymeres have been determined with broilers, aged 2–3 and 5–6 weeks as well as adult cocks. The age of the animals and the shares of the fatty acids were of high influence on the feeding value. In the second trial the fattening performance of broilers that had got ratios of 13 different frying oils, bleaching earth oils or distillation residues, was determined. The results with frying oils were successful, those with bleaching earth oils were moderate and with distillation residues extremely bad. A dependence between the content of polymeres and the feeding value of fat and oils could not be found out.     

Bleaching practices in the U.S.

The differences between European and U.S. vegetable oils with respect to their influence on bleaching requirements are discussed. Based on the information supplied by over 50 refiners, a summary gives an insight into bleaching conditions with earth and heat. These data are condensed in a chart relative to most used oils and fats. General information on pre-and post-bleach is also indicated.     

Bestimmung der Aktivität von Bleicherden,insbesondere im Hinblick auf ihre Verwendung zur Qualitätsbeurteilung vegetabilischer Öle I

Determination of the Activity of a Bleaching Earth with Respect to its Application in the Quality Assessment of Oils I One of the surest tools for the determination of freshness of raw oils is the determination of extinction in diene and triene region. The oxydative changes, which are rarely detected by the usual analytical characteristics, can be easily recognized in a bleach-test by treating the oil with a definite amount of bleaching earth followed by measurement of increase or decrease in extinction. The general application of this procedure was not feasible till now because the activity of the bleaching earth used for this purpose was unknown or only roughly known. For the determination of the activity of bleaching earths with sufficient accuracy a simple method was developed, which consists of treatment of the bleaching earth with castor oil. The reproducibility of the bleach-test could thus be appreciably improved.     

A kinetic model for bleaching vegetable oils

Very little data and very few kinetic models are available describing and evaluating the performance of bleaching processes, earths, and equipment. This work presents a general kinetic model for the adsorption of pigments by adsorbent earths in several edible oils. It reports the kinetic parameters found for two bleaching earths (one developed in the laboratory and one commercial) for the clarification of soybean oil, as well as their activation energies. The proposed kinetic model is second order in the dimensionless pigment concentration and is in good agreement with our experimental data. A very simple mechanistic explanation based on adsorption/deactivation is offered to justify its application. We also present mathematical modeling based on balance equations to show how the kinetic parameters can be used for bleaching earths and for industrial equipment evaluation and design, such as for the transient fed-batch stirred bleaching vessel. The model seems appropriate to represent data under different operating conditions such as temperature and adsorbent load. The simulation shows that startup procedures are very important in the bleaching process—at least as important as the batch step, in which the oil color reaches its desired standard.     

Bleaching of edible fats and oils

Almost all fats and oils are subjected to so‐called bleaching during processing. Originally bleaching was only used to reduce the colour. Today, however, the bleaching step is used mainly to remove or convert undesired by‐products to harmless ones from fats and oils. This will guarantee that such compounds do not interfere with the processing and that the requirements for human food are being met.     

Studien zur Korngrößenverteilung von Bleicherden

Studies in Particle Size Distribution of Bleaching Earths The particle size distribution of various German and American bleaching earths was determined to check whether a relation exists between size distribution and technical properties of the earths. The results of determinations obtained by sieving-, sifting-, and sedimentation methods was surprising: the obtained size distribution depends on the method to such a degree that it was impossible to specify the “real” particle size and the functional value of the earths. It is recommended to the consumer to determine as before only these data which concern directly the scope of the earths.     

Some fundamental aspects of bleaching

This paper reviews several aspects of bleaching fats and oils. Bleaching is a relatively simple operation from a mechanical standpoint, however the underlying technical background of the reactions occurring in the oil is quite involved and frequently weird, and apparently inconsistent effects result. Specificially, the subjects covered are: (a) effect of bleaching upon the organic peroxides of the oil; (b) nature of the bleaching reaction; (c) variation of bleaching efficiency between clays upon different oils; and (d) filtration factors. Presented at the AOCS meeting in New Orleans, April 1970.     

Classification of feeding fats by FT‐IR spectroscopy

In this paper, a technique useful for the classification of different food oil co‐ and by‐products of potential use for feed preparation is shown. The proposal is based upon a Fourier transform infrared evaluation of different classes of compounds, and its elaboration was carried out starting from the knowledge of the chemical composition of each feedstock category. Using this technique, a sure classification of fatty acid calcium soaps, fully hydrogenated fatty acids, lecithins, acid oils from chemical refining, acid oils from physical refining and fish oils can be easily done. The remaining categories of animal fats, fried oils and oils recovered from exhausted bleaching earth can be differentiated by using one or two additional chemical tests. The scope of this paper is to provide a quick, easy and non‐expensive tool for a correct classification of feedstock, in order to allow the choice of correct and applicable analytical tests for the evaluation of the quality and of the composition of each sample.     

The function of bleaching earths in the processing of palm,palm kernel and coconut oils

The results presented in the literature, which attempt to elucidate the mechanisms by which triglyceride oils are bleached by earths, are reviewed. The impact of this work and how the mechanistic proposals affect changes in oil properties are considered, with particular emphasis on the needs of the palm oil processor. Important properties include color, metals and phosphorus content and oxidative stability of the oil. Investigations made in our own laboratories have been aimed at elucidating the effect of varying physical and chemical properties of the bleaching earth on the quality of bleached and deodorized oils. Techniques used in this work are pore-size distribution, surface area, scanning and transmission electron microscopy and a variety of chemical and X-ray analysis methods. The ability to vary such parameters in montmorillonite clays by alteration of process conditions to give materials with specific performance characteristics is demonstrated. Comparisons are made between acid-activated montmorillonites and other clay types.     

Refining,bleaching and hydrogenating meat fats

Meat fats are most often steam refined. This has been the accepted practice for at least 35 years. Meat fats are caustic refined for a few specialized products. The caustic refining conditions differ from those used for vegetable oils primarily in the amount of mixing used after the addition of caustic. Bleaching of meat fats is accomplished easily. Most meat fats are light in color and require clarification more than bleaching. The green color of tallows containing large amounts of chlorophyll is easily removed with activated earth. Meat fats are hydrogenated to develop the SFI curves needed for various products and also are hydrogenated to saturation for use as plasticizing agents. The hydrogenation of lard and tallow is not as complicated as that of most vegetable oils, because the original fat is more saturated and the reaction has fewer possible routes to follow.     

Disterylether – Artefakte der Fettbleichung

Disteryl Ethers – Artifacts of Bleaching of Fats and Oils (1) Disteryl ethers are formed by acid catalyzed dehydration of Δ⁵-unsaturated sterols during the bleaching of fats and oils with acid-activated bleaching earths. These artifactual lipids can be used as markers of the bleaching process. Distanyl ethers can be produced by catalytic hydrogenation of Δ^5,5'-unsaturated disteryl ethers. (2) Spectroscopic characterization of disteryl ethers and distanyl ethers showed that these steroidal lipids are highly symmetrical compounds with the oxygen atom of the ether linkage in the center of symmetry. Conformation of C-O bonds at the ether bridge is 3β/3'β showing that both types of compounds are periplanar and voluminous molecules. (3) Mixtures of disteroid ethers are separated by silver ion HPLC into the unsaturated disteryl ethers and the saturated distanyl ethers. Individual components of these two classes of disteroid ethers are separated by capillary GLC. Determination of individual compounds may be a conclusive proof of bleaching and hydrogenation of fats and oils. (4) Di[4,4'-¹⁴ C]cholesteryl ether and di [4,4'-¹⁴C]sitosteryl ether, intragastrically administered to mice, were found to be neither absorbed nor metabolized in the gastrointestinal tract. Both dicholesteryl ether and disitosteryl ether, fed to mice at a level of 400 mg/kg body weight x day for 4 weeks, did not lead to ill effects in the animals.     

Determination of Raffination of Edible Oils and Fats by Olefinic Degradation Products of Sterols and Squalene,Using Coupled LC-GC

Raffination of edible oils and fats, i.e. bleaching with earth or charcoal as well as deodoration, can be determined by the analysis of dehydroxylation products of sterols and isomerization products of squalene. These olefinic degradation products are isolated from the rest of the oil by LC on silica gel and on-line transfer to GC. Sample preparation consists of preparing a 20% solution of the oil. Nearly half of the “extra virgin” olive oils analyzed contained such products, but concentrations were too low for assuming admixture of regularly refined oils. However, many other oils advertized as non-refined turned out to have been treated beyond declaration.     

Untersuchungen zur Entölung von Bleicherde mit überkritischem Kohlendioxid

Investigations on De-oiling Bleaching Clay by Supercritical Carbon-Dioxide Refining edible fats and oils, an adsorbent accrues during the bleaching process, which contains oil up to 40% by weight. As disposal of this contaminated material is problematic, it has more and more been taken into consideration to deoil and to recycle the bleaching clay. Up to now, the methods of deposition, extraction with hexane, and scorching have been applied. Our investigations to decontaminate the bleaching clay were carried out by means of high pressure extraction using carbon dioxide as a solvent. For this purpose, bleaching clays from the refinement of rape seed oil and palm oil were investigated. During the CO₂-extraction of the earth, pressure and temperature have been varied and, during the separation process, the number of separation steps in addition. Furthermore the CO₂-mass flow has been altered. Besides of deoiling the bleaching earth as far as possible, the experiments aimed to recover the oil in good quality and to restore an operational bleaching clay. The results of the kinetic investigations revealed that the bleaching clays react differently to variation of the extraction parameters. While it is possible to determine an optimal operating point of the experimental set up for the bleaching clay of palm oil, it is not for the bleaching clay of rape seed oil. The results of the analysis of the extracted oils, palm oil and rape seed oil, are comparably good. The CO₂ extraction delivers a selectively extracted oil. On the contrary, the residual activity of the bleaching clays is a different one, i.e. at most 50% of the activity of fresh bleaching clay.     

Adsorptive Removal of Sulfur from Canola Oil

The presence of sulfur compounds in canola oil is mainly responsible for nickel catalyst poisoning during hydrogenation. In this study, different adsorbents (alumina, alumina-silicate, diatomaceous silica and silica gel) were used in conjunction with different bleaching earths (AOCS official natural bleaching earth, G 160 from Harshaw-Filtrol and montmorillonite K 10 from Aldrich Chemical Co.) to remove the three types of sulfur compounds [total sulfur(TS), Raney nickel sulfur (RS) and volatile sulfur (VS)] from canola oil. The TS content of the oil was not affected during bleaching. The AOCS bleaching earth removed 28.6-36.4% RS and 57.8–78.9% VS in the bleaching temperature range of 120–150°C. The some bleaching earth, in combination with 6% TriSyl (micronized silicon dioxide adsorbent) 45.7–81.4% RS and 73.3-95.6% VS were successfully removed. TriSyl also improved the chlorophyll content and color of the oil bleached at 120°C. Bleaching at 120°C with G 160 and K 10 removed 44 and 81%%RS and 69 and 61% VS respectively. These two bleaching earths, in combination with alumina, alumina-silicate, diatomaceous silica or silica gel did not further improve the removal of all the three types of sulfur present in the oil.