Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...
Reexamination Certificate
2001-10-20
2003-06-17
Carr, Deborah D. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Fatty compounds having an acid moiety which contains the...
C554S184000, C554S175000
Reexamination Certificate
active
06579996
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for removing free fatty acids from fats and oils of biological origin or their steam distillates by extraction.
2. Description of the Related Art
In human nutrition, and as raw materials for the chemical industry, oils and fats of biological origin play an important role. For example, they serve as raw materials for production of surfactants, plasticizers, waxes, lubricants, fatty alcohols etc. Essential components of fats and oils are the triesters of glycerides and fatty acids, the so-called triglycerides. The physical properties of fats and oils are determined a) by the chain length of the fatty acids, b) by the degree of saturation of the fatty acids and c) by the distribution of the various fatty acids on the three hydroxyl groups of the glycerol. Fats having a high saturated fatty acid content are generally solid at ambient temperature. Fats or oils, respectively, from predominantly unsaturated fatty acids are liquid at ambient temperature.
The fats and oils of biological origin comprise a number of secondary products which adversely affect the keeping quality, odour, flavour and appearance. The most important secondary products are: suspended matter, organic phosphorus compounds, free fatty acids, pigments and odour compounds. Mucilaginous material (gums) and other complex colloidal compounds can promote hydrolytic degradation of fats and oils during their storage and interfere during further refining. Therefore, they are removed by the process of what is termed degumming. Degumming is based on hydration with water or direct steam. The organic phosphorus compounds (phosphatides) take up water in the course of this, swell and become insoluble.
After phosphorus compounds and suspended matter have been removed by degumming and, if appropriate filtration, the further object is to separate off free fatty acids and pigments and odour compounds. Commercial crude fats and crude oils comprise on average from 1 to 3% by weight of free fatty acids, high-grade types 0.5% by weight or less, some palm, olive and fish oils 20% by weight or more. The fatty acid content of the refined fats and oils is, by comparison, generally to be below 0.1% by weight. Whereas relatively long-chain free fatty acids do not usually cause flavour impairment, the short-chain fatty acids have a soapy, rancid flavour. In practice, the deacidification performed for removing the free fatty acids is predominantly carried out by treatment with aqueous alkali solutions or by steaming at temperatures of approximately 220° C. Removing the free fatty acids by esterification with glycerol or a monohydric alcohol, by selective solvent extraction or by adsorbents, is of lower importance, by comparison. Below, the deacidification processes known hitherto are described in more detail.
The treatment with alkaline solutions, as the method most employed, can be carried out batchwise or continuously. The higher the lye concentration, the more readily are unwanted accompanying substances taken up into the resulting soap, termed the soapstock. Weakly alkaline solutions are generally sprayed onto the oil at 90° C. and percolate downwards through the heated oil. In contrast, stronger lyes (4n to 7n) are usually stirred into the oil at from 40 to 80° C. After the deacidification and removal of the soapstock, the oil or fat is washed with highly dilute lye (approximately 0.5n) and thereafter with water, in order to remove soap residues down to at least 0.05% by weight. With the use of centrifuges, a completely continuous plant for neutralizing fats and oils can be constructed according to this method. If the fats and oils to be deacidified have a high content of free fatty acids, the deacidification using alkaline solutions leads to a relatively hard soapstock which can only be removed from the plant with difficulty.
Therefore, what is termed steam deacidification has been developed as an alternative In this process, which is also termed physical refining or deacidification by distillation, the free fatty acids are likewise continuously removed from the crude oils by hot steam under vacuum. This process does not depend on the free fatty acids being distilled off completely, since fatty acids remaining in a small amount can expediently be removed by a secondary lye refining. Before the deacidification by distillation, the crude fat must, however, be freed as completely as possible from gums, phosphatides and metal traces—usually by treatment with phosphoric acid—since the accompanying substances can lead, during the distillation, to dark, unpleasant-tasting substances, which can then virtually no longer be removed. The steam deacidification takes place at relatively high temperatures; for example palm oil is deacidified by superheated direct steam at 220° C. The high temperature destroys a great number of substances which are present in the oil (or fat) and are desirable per se, for example the antioxidants which improve the keeping quality of the oil, or forces these substances into what is termed the steam distillate which is produced after condensation of the superheated steam used for the deacidification.
The neutralization of oils and fats by separating off the free fatty acids from the crude fat by means of selective solvents is another method which is suitable, especially, for high-acidity oils and fats. For example, liquid extraction using ethanol makes possible the deacidification of olive oil having 22% by weight of free fatty acids down to approximately 3% by weight of free fatty acids. Another extraction medium which dissolves, at suitable temperatures, only free fatty acids and very highly unsaturated triglycerides, is furfural. In yet another process, the Selexol process, liquid propane is used as extraction medium in countercurrent. Liquid propane selectively dissolves saturated neutral oil, while fatty acids, oxidation products, unsaponifiables and highly unsaturated glycerides are hardly dissolved at all and remain behind. This process is chiefly used for fractionating fish oils and fish liver oils.
The selective extraction process is used industrially virtually exclusively for fats having a very high free fatty acid content. Examples of these are: cocoa butter from shells, olive oil from the press cake, low quality grades of rice oil and cottonseed oil. The alcohol used in this process is isopropyl alcohol. To deacidify one ton of oil, Bernardini (E. Bernardini, Oilseeds, Oils and fats, Publishing House Rome, 1985) quotes the following levels of consumption: energy and auxiliaries, steam 800 kg, electrical energy 14 kWh, hexane 15 kg, isopropanol 18 kg. Oil produced in this manner is not used as edible oil.
Although the degumming and alkali refining already lead to a certain clearing, generally, a decolourizing stage is further provided. Decolourizing is customarily performed using solid adsorbents, such as bleaching earth and activated carbon. Bleaching with air or chemicals plays a minor role in edible fats.
In the last phase of the refining process, odour and flavour substances are removed from the deacidified and bleached oils and fats. Deodorization is essentially a steam distillation in which the volatile compounds are separated off from the non-volatile glycerides. The odour and flavour substances are predominantly aldehydes and ketones which are formed by autoxidative or hydrolytic reactions during the processing and storage of the fats and oils. The low partial pressure of the compounds to be removed requires that the steaming is carried out under reduced pressure. Steaming is usually carried out from 180 to 220° C. and a pressure of from 6 to 22 mbar.
For environmental protection reasons, wastewaters from the alkaline deacidification must be carefully treated, which is associated with costs. Therefore, most recently, the interest in physical processes for refining oils and fats has been revived. As early as in the 1920s, the possibilities of deacidification using liquid-liquid extraction with aqueous lower
Drescher Martin
König Wolfgang
Peter Siegfried
Weidner Eckhard
Carr Deborah D.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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