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.     

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.     

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.     

Körnungsaufbau und Filtrationseigenschaften von Tonsil-Bleicherden

Particle Structure and Filtration Properties of Tonsil Bleaching Earths The particle structure of bleaching earths influences the bleaching process of oils and fats both during adsorption and filtration. The adsorptive properties of a bleaching earth are improved with decrease in particle size, but the filtration properties are impaired. The bleaching earth must have an optimum particle composition in order to ensure good adsorption and rapid filtration yielding a clear filtrate. In this context, the difficulty in the determination of particle size distribution of bleaching earths is emphasized. Moreover, the influence of water content of Tonsil bleaching earths and that of the amount of bleaching earth used the filtration and adsorption is reported. Possible alterations in the particle composition of bleaching earths during transport or pumping in admixture with oils or fats are discussed.     

Zur Bleichung pflanzlicher Öle II: Kinetik des Bleichprozesses

Bleaching of Vegetable Oils II.: Kinetics of the Bleaching Process The study deals with the kinetics of bleaching. The test-system used rapeseed oil with a low content of erucic acid and added bleaching earth Tonsil Optimum FF. By means of the results obtained an empiric equation was then developed describing the process taking part under the conditions studied.     

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.     

Decolorisation of crude palm oil by acid-activated spent bleaching earth

Regeneration of spent bleaching earth by acid activation and heat treatment has been investigated. Spent bleaching earth was activated by H₂SO₄ of various concentrations (1–40%) and heat treated at 120°C–350°C. The experimental results indicate that treatment of spent bleaching earth with 10% H₂SO₄ at 350°C produced a material which was most effective in removing coloured pigments from crude palm oil. Subsequent experiments were conducted using this particular acid-treated spent bleaching earth. Various parameters which affect the sorption process were studied. They include initial crude palm oil concentration, sorbent dosage and temperature. Applicability of both the Freundlich and Langmuir isotherms to the acid-treated spent bleaching earth–palm oil hexane miscella system indicates that both physiosorption and chemisorption were involved in the sorption process. Measurements of various quality parameters of bleached and crude palm oils were carried out. They include Lovibond Colour index, carotene content, peroxide value, free fatty acid, fatty acid composition and iodine value. The results show that the bleached palm oil retained good oil quality after the decolorisation process using 10% acid-treated spent bleaching earth with a Lovibond Colour of 6·4. © 1998 SCI     

Beeinflussung des Bleichprozesses bei Pflanzenölen

Influencing the Bleaching Processes of Vegetable Oils The report describes the influence of the acid-, water- and bleaching earth concentration to the parameters lovibond red, the content of carotene, phosphorus and heavy metals, the peroxid-, the anisidine- and extinction value at 232 nm. As an acid the citric acid has been used in different concentrations. After a bleaching process at 90°C the palm oil was bleached in a heat-bleaching-process at 260°C and a pressure of 1 mbar. The possibility of getting good bleaching with 0.5% bleaching earth by optimizing the bleaching process will be shown.     

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.     

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.     

Regeneration of a spent bleaching earth and its reuse in the refining of an edible oil

A spent bleaching earth from an edible oil refinery has been regenerated by thermal processing followed by washing with a solution of hydrochloric acid. Optimal regeneration conditions have been controlled by decolorization tests of a degummed and neutralized crude edible oil. Optimal values (temperature: 500 °C, carbonization time: 1 h, HCl concentration: 1 M ) gave a material as efficient as a virgin bleaching earth. The percentage uptake of chlorophyll derivatives and β‐carotenoids calculated at 410 and 460 nm, are respectively 92.8 and 95% for an oil processed by the regenerated spent bleaching earth, against 77.4 and 92.7% for the same oil processed by a commercial virgin bleaching earth. The results obtained after decolorization of an edible oil with a regenerated spent bleaching earth indicate that during the process, the resultant oil did not undergo any changes in the iodine value, the free fatty acid content and the saponification value. © 2000 Society of Chemical Industry     

Untersuchungen zur Verfahrensentwicklung der Speiseöl-Bleichung unter Einsatz der Hochdruck-Technik

Investigations on the Bleaching Process of Edible Oils using High-Pressure Technology The four process steps de-gumming, neutralization, bleaching and deodorization of the refining of vegetable oils, gained by extraction or mechanical fluid-solid separation, are necessary to attain a product of food quality. During the bleaching an oiled adsorbent accumulates which has to be disposed after use. The investigations about de-oiling and recycling of the adsorbents and oil-recovery led to two alternatives to teh conventional bleaching process. The adsorption from the supercritical fluid phase enables the integration of the bleaching into the cycle process of high-pressure-extraction of oil seeds. Our investigations show that oils can be bleached in an adsorbent bed even with a short time of direct contact without oiling the adsorbent. Furthermore the adsorption in the fluid phase with inert gas pressure up to 10 MPa is a possible pressure-bleaching for traditionally gained oils. Especially at supercritical conditions of the CO₂ used, the pressure bleaching shows an accelerated kinetic behaviour and a a reduction of the necessary dosage of bleaching clay.     

Refining and Bleaching of Peanut Miscella

The effects of type of crude miscella, oil content in miscella, concentrations of caustic soda solutions, method of mixing and temperature on the refining of high f. f. a. dark coloured peanut miscellas were investigated. Very effective removal of free fatty acids and decolorisation of the peanut miscellas were achieved by treating at 45-60% oil content with 16°-20° Bé caustic soda solution at room temperature (ca. 32 ± 1° C). Good bleaching of refined miscella samples also at room temperature with commercial acid treated earth and active charcoal was possible. Refined oils had 0.02-0.06% f. f. a. with 94-99% colour removed. Successful commercial possibilities are indicated.     

Bleaching rapeseed and soybean oils with synthetic adsorbents and attapulgites

Efficiencies of synthetic adsorbents and attapulgites in bleaching alkali-refined rapeseed and soybean oils ranged from 13–53% and 93–97%, respectively. The Freundlich equation was more applicable than the Langmuir equation to the experimental adsorption isotherms of β-carotene on attapulgites. Bleaching with attapulgites reduced tocopherols by 12.5–29.5% in rapeseed oil and by 18.9–44.8% in soybean oil. Cosmetic-grade attapulgite was superior to the others in bleaching efficiency, equilibrium amount adsorbed and removal of free fatty acids.     

The quality and volatile‐profile changes of camellia oil (Camellia oleifera Abel) following bleaching

Bleaching is a necessary step in the production of refined camellia oil (Camellia oleifera Abel) since crude oil has a dark brown color, due to pigments extracted from the seed coat during pressing, which is unacceptable to consumers. In order to understand the quality change and oxidative state of camellia oil in the bleaching step, measurements of various quality parameters, i.e. peroxide value (POV), free fatty acids (FFA), UV absorbance, and the volatile profiles of crude and bleached oils, were carried out. The results showed that FFA, K₂₇₀, and K₂₃₂ increased, whereas POV decreased, with increase of the activated earth dosage of 0–4% and of bleaching time from 0 to 40 min at 110 °C. As the amount of activated earth was increased from 0 to 4% with bleaching at 110 °C for 30 min, various classes of volatile compounds increased in concentration: aldehydes (23.7 µg/g), alcohols (13.2 µg/g), esters (8.0 µg/g), alkenes (2.0 µg/g) and ketones (1.9 µg/g). Likewise, when bleaching was carried out at 110 °C with 3% activated earth and the bleaching time varied between 0 and 40 min, the concentrations of volatile compounds also increased: aldehydes (27.7 µg/g), alcohols (18.2 µg/g), esters (7.3 µg/g), ketones (3.2 µg/g) and alkenes (0.6 µg/g). These findings indicate that hydroperoxides in the oil were decomposed into lower‐molecular‐weight products in the process of bleaching and that the extent of this decomposition can be controlled by time and amount of activated earth.     

Physical and chemical properties of alumina bleached cottonseed oil

No detectable amount of polymerization or triene conjugation occurred on bleaching refined cottonseed oil with either activated alumina or with sulfurous acid-treated alumina, although insignificant amounts of diene conjugation andtrans- isomerization occurred. AOM stability, tocopherol content, and fatty acid composition, as determined by gas-liquid chromatography (GLC), were comparable with values obtained with oil bleached with natural earth. Hydrogenation of the oils proceeded normally. Taste panel evaluations of the deodorized oils revealed their flavor stability to be equal to that of the same oil bleached with AOCS official earth.     

Über die kontinuierliche Behandlung mit aktivierter Bleicherde bei der Raffination von Aromaten

Continuous Process for the Treatment with Activated Bleaching Earth During Refining. A new process for continuous bleaching which has been employed since the middle of 1973 in Southwest Germany for bleaching 150 to of soybean oil per day is described. A unique feature of this process is that the consumption of bleaching earth is reduced although the product is subjected to milder thermal treatment.     

Zur Bleichung pflanzlicher Öle III: Kontinuierliche Anordnung des Bleichprozesses

Bleaching of Vegetable Oils III: Continuous Bleaching The bleaching of vegetable oils can be carried out in either a batch or a continuous way. When the continuous procedure is performed, fresh oil and adsorbent are supplied to the system, while the bleached oil (containing different concentration of colour substances) and the used adsorbent are carried off. The kinetics of the batch bleaching has been described in literature, but the data concerning the continuous bleaching are hardly available. The present study discusses particular relations concerning the continuous bleaching arrangements.     

Bleaching of alkali-refined vegetable oils with clay minerals

Bleaching efficiencies of bentonites, montmorillonites and sepiolites for alkali-refined rapesseed, soybean, wheatgerm, safflower, corn, cottonseed and sunflower oils were investigated by a batch method at 110°C. The sepiolites with more acid sites at −5.6 < H_o ≥ −3.0 were the most effective in bleaching of each alkali-refined oil. Surface area and acidity at −5.6>H_o ≥ −3.0 were highly significant with bleaching efficiency. The sepiolites (numbers 2 and 3) were more suitable than standard activated clay because they were more effective both in retaining tocopherols and in reducing free fatty acids after bleaching.     

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.