How are fatty acids extracted from plants

DE4326399C2 - Process for the extraction of fats and oils - Google Patents

Process for the extraction of fats and oils


Publication number
DE4326399C2DE4326399ADE4326399ADE4326399C2DE 4326399 C2DE4326399 C2DE 4326399C2DE 4326399 ADE4326399 ADE 4326399ADE 4326399 ADE4326399 ADE 4326399ADE 4326399 C2DE4326399 C2DE 4326399C2
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DE4326399A1 (de
Juergen Dr Heidlas
Jan Dr Cully
Heinz-Ruediger Dr Vollbrecht
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SKW Trostberg AG
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SKW Trostberg AG
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  • 239000003925fatSubstances0.000titleclaimsdescription28
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    • C11B1 / 00 — Production of fats or fatty oils from raw materials
    • C11B1 / 10 — Production of fats or fatty oils from raw materials by extracting
    • C11B1 / 104 — Production of fats or fatty oils from raw materials by extracting using super critical gases or vapors


The present invention is a process for the extraction of fats and oils from natural substances such. B. vegetable, animal or microbial starting materials with the help of liquid propane as a solvent, this process relates to the extraction of fats and oils as well as to the production of defatted or de-oiled products, which are low-fat and therefore low-calorie products in the food sector are becoming increasingly important.
In principle, there are two methods available for degreasing and de-oiling, for example, vegetable products: extraction and pressing. From an economic point of view, pressing is only advantageous if the fat and oil content of the starting material is relatively high (<25% by weight). However, even when the process is optimally used, a residual fat content of at least 4 to 5% by weight remains in the press residue. In contrast, extractive processes with normal organic solvents such as. B. hexane or mineral spirits are also suitable for starting products with a low fat content, whereby the residual content in the residue can generally be reduced to less than 1% by weight. The disadvantage of conventional solvent extraction is the fact that most solvents are not toxicologically harmless and that the extracted fats and oils and the extraction residues must be largely solvent-free before they can be used for food or feed purposes. This requires comparatively high temperatures, which can negatively affect the sensory properties of the products.
For the degreasing of animal raw material such. B. fatty meat is the separation of the greatest technical importance. In this process, after a thermal or mechanical digestion of the educt, the difference in density between meat and fat components is used to carry out a separation in separators or decanters. For economic reasons, this process cannot be used to produce products from fatty meat with a fat content below 10%, as otherwise the meat losses are too high. For the production of meat products with a lower fat content, extractive processes must therefore be used which, in the case of the use of organic solvents, have the disadvantages already mentioned.
To circumvent this problem, extraction with compressed gases has been introduced in recent years, especially for the extraction of sensitive natural substances, with carbon dioxide (CO2) has prevailed as the extraction medium. The extraction of fats and oils with supercritical CO2 Because of its low dissolving power, it is only satisfactory in very high pressure ranges (<500 bar), which is technically complex and consequently cost-intensive and therefore only suitable for products with a very high added value. This disadvantage can also be caused by the addition of entrainers to CO2 can only be partially compensated, whereby the additional control effort for the entrainer dosing is to be regarded as a further disadvantage.
As an alternative to CO2 According to the state of the art, compressed propane has also been proposed as a solvent for the extraction of fats and oils. Thus, according to DE-PS 28 43 920, the extraction is carried out at supercritical pressure (42 bar) and supercritical temperature (97 ° C), while in several publications (US-PS 4,331,695, DE-PS 23 63 418, US PS 3 939 281, DE-PS 22 55 567, DE-PS 22 55 566) an extraction pressure close to or above the critical pressure and subcritical extraction temperatures are recommended. According to US Pat. No. 2,560,935 and US Pat. No. 2,682,551, liquid propane is also disclosed as a solvent for oils and fats, but no specific information is given with regard to the extraction pressure. Finally, US Pat. No. 2,254,245 describes fat extraction at very low temperatures (<0 ° C.), while US Pat. No. 1,802,533 recommends a maximum extraction pressure of 7 bar. Critical state parameters were also often chosen for the separation of the extracted lipids, whereby a phase separation into an oil-rich and an oil-poor propane phase is used in this state range in order to separate or fractionate the oil (cf., for example, US Pat. No. 2,660,590 or US Pat. PS 2,548,434).
These known processes all have disadvantages: On the one hand, under critical and supercritical conditions, extraction results are achieved in which the quality of the extracted oil or fat is greatly reduced by high thermal stress. On the other hand, extraction with liquid propane is selective in pressure ranges of <10 bar, but the mass transfer during extraction is limited, so that longer extraction times and larger amounts of extractant are required to achieve the extraction goal of degreasing or de-oiling.
The present invention was therefore based on the object of developing a process for the extraction of fats and oils from natural substances with the aid of propane as a solvent, which does not have the disadvantages of the prior art mentioned, and which, without great technical effort, also allows adequate gas treatment with fats and oils as well as a good sensory quality of the products.
According to the invention, this object was achieved by carrying out the extraction at a pressure of 10 to 30 bar and a temperature of 10 to 55 ° C and separating the extracted fats and oils from the solvent by lowering the pressure and / or increasing the temperature to 80 ° C . Surprisingly, it has been shown that in this relatively narrow pressure and temperature range, optimal conditions are found for the extraction of fats and oils with liquid propane, because not only good extract yields but also high-quality extracts are obtained which have little or no Contains quantities of undesirable accompanying substances. This is so surprising because compressed gases in the liquid (subcritical) state i. a. less favorable extraction properties than, for example, gases in the critical or supercritical state. In addition, an unnecessarily high extraction pressure (<30 bar) is avoided, which can significantly reduce investment and operating costs.
In principle, all natural substances containing fat or oil on a vegetable, animal or microbial basis can be used for the process according to the invention. Examples of vegetable fats or oils are olive oil, palm oil, bamboo fat, coconut fat, cocoa butter, coffee oils, peanut butter, rapeseed oil, flax oil (linseed oil), sunflower oil, wheat germ oil, rice germ oil, cottonseed oil, corn germ oil, soybean oil, palm kernel oil and pumpkin seed oil. Animal products include, for example, beef or veal as well as marine animal oils such as B. fish oils in question. Finally, the method according to the invention can also be used for fermentation residues, for example from yeast, fungi or bacteria.
To increase the extraction yield, it is advisable to use the extraction material in comminuted, pelletized form. Should the (especially solid) starting material have a high water content such as e.g. B. meat or fermentation residues, it has proven to be particularly advantageous to reduce the moisture content by suitable drying methods prior to extraction to below 50% by weight.
It is to be regarded as essential to the invention that the extraction with liquid propane is carried out in a very narrow and defined pressure and temperature range, which is 10 to 30 bar and 10 to 55 ° C. An extraction pressure of 15 to 25 bar and an extraction temperature of 20 to 45 ° C. are preferably used. In any case, the extraction pressure and temperature must be coordinated so that the propane is in the liquid state.
At pressures <30 bar, the extraction properties of the liquid propane become increasingly unselective, especially when extracting oil seeds. H. unwanted dyes and unsaponifiable fractions are also extracted, which greatly reduces the quality of the extracted oil. With increasing extraction temperature (close to or above TK) there is also the risk that, especially with oils with a high content of polyunsaturated fatty acids, undesirable reactions occur in the complex natural substance matrix of the starting material (and thus the extract yield decreases) and, on the other hand, undesirable isomerizations at the double bonds of the polyunsaturated fatty acids (formation of cis, trans conjugated double bonds), which negatively influence the nutritional value of the product.
The amount of propane gas used can be varied within wide limits and depends essentially on the amount of oil or fat to be extracted. Depending on the type of starting material, 2.5 to 500 g of liquid propane are normally required per g of fat or oil to be extracted. The maximum gas loading with lipid substances under these extraction conditions is 5 to 25% by weight, depending on the type of fat or oil extracted.
The purity of the propane gas used is relatively uncritical in most cases, i. H. there can also be significant amounts of impurities from homologous hydrocarbons (caused by the refining process) without any noticeable loss of quality. Propane is preferably used in a technical purity of approx. 90% and in deodorized form. The extraction with liquid propane can in some cases also be carried out in two stages in order to obtain the complete extraction of the fats or oils.
The propane gas is preferably circulated so that the desired lipid substances can be loaded several times, but it is also possible to contact the extraction material only once with the extraction medium. In order to achieve high economic efficiency of the process, several extraction autoclaves can be connected in series and the extraction medium can flow through them one after the other. The maximum gas loading of the liquid propane can always be optimally used by appropriately switching the sequence of these autoclaves (e.g. flow through after an advanced degree of extraction).
Following the extraction, fats and oils dissolved in the liquid propane are separated out by lowering the pressure and / or increasing the temperature, a pressure decrease to 30 bar and a temperature increase to 80 ° C. having proven particularly advantageous. In this way it is ensured that no undesirable reactions such. B. Isomerizations of the double bonds of polyunsaturated fatty acids take place during the deposition. According to a preferred embodiment, the deposition takes place by isobaric evaporation of the solvent, which can decisively increase the economic efficiency of the process.
With the aid of the method according to the invention, high-quality products with regard to color, smell or taste can be obtained in good yield and under mild conditions. Because of the comparatively low technical complexity, this process is also well suited for use on an industrial scale.
The following examples are intended to explain the invention in more detail.
200 g of pre-defatted cocoa (granules 1 to 2 mm in size, fat content approx. 11%) were extracted in a pressure autoclave at 20 bar and 25 ° C. with compressed propane in the effluent.
After 1 kg of propane had flowed through, no more cocoa butter was deposited while the gas was continuously released to atmospheric pressure. The residual fat content in the granulate was <0.3%; the yield of extracted cocoa butter was 2.2 g.
140 g of ground flaxseeds (oil content approx. 41%) were extracted in a pressure autoclave at 20 bar and 25 ° C. with compressed propane in the effluent. After 0.7 kg of propane had flowed through, 50 g of oil were extracted (corresponds to 87% degreasing). After a second grinding of the residue (fat content approx. 8%), extraction was carried out with a further 0.15 kg of propane under the same conditions, with almost complete de-oiling of the residue being achieved. The oil was separated out in both stages by continuously expanding the gas to atmospheric pressure. A residual oil content in the residue could not be determined by Soxhlet extraction with hexane (8 h); the yield of oil was 57.5 g.
1 kg of pretreated soy flakes (oil content approx. 18%) were extracted in a pressure autoclave at 30 bar and 45 ° C. with compressed propane. The extraction was carried out continuously in a cycle, the oil being separated off by isobaric evaporation of the propane at 80 ° C. in the separator before the unloaded propane (cooled to 45 ° C.) flowed through the extraction material again. After a total of 7 kg of propane had flowed through the soy flakes, the extraction was terminated. The residual oil content of the residue was below 1%; the yield of oil was 175 g.