WO2009148919A1

WO2009148919A1 - Methods for refining oil

Info

Publication number: WO2009148919A1
Application number: PCT/US2009/045480
Authority: WO
Inventors: Aharon Eyal; Alexander Patist; Ian Purtle; Asher Vitner
Original assignee: Cargill, Incorporated
Priority date: 2008-06-06
Filing date: 2009-06-03
Publication date: 2009-12-10
Also published as: AR073935A1

Abstract

A method for refining oil that includes extracting an oilseed with at least one organic solvent to form oil miscella comprising triglyceride(s), organic solvent(s), phospholipid(s), and fatty acid(s); contacting the oil miscella with at least one of (i) water or (ii) an aqueous solution to form a medium having at least two immiscible phases, wherein at least a fraction of at least one of the immiscible phases is dispersed in the other immiscible phase; coalescing the dispersed immiscible phase; separating the immiscible phases to generate a separated lipophilic product comprising the triglyceride(s) and the solvent(s) and a separated hydrophilic coproduct comprising water, the phospholipid(s), and the fatty acid(s), wherein centrifugation is not used for the separating the immiscible phases.

Description

METHODS FOR REFINING OIL

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of the United States Provisional Patent Application, Serial No. 61/131,161, filed June 6, 2008, entitled METHODS FOR REFINING OIL, which is hereby incorporated by reference in its entirety.

FIELD

[0002] Disclosed herein are methods for refining of oil, particularly oil miscella.

BACKGROUND

[0003] The primary components of most vegetable oils are triglycerides. Depending on the oil source, these triglycerides may include a variety of saturated, partially saturated, and unsaturated fatty acids (e.g., oleic, linoleic, linolenic, lauric, palmitic, and myristic acids) esterified on a glycerol molecule in various combinations. Raw, unprocessed vegetable oils also often contain varying amounts of other compounds. Some of these compounds are desirable components of the oil, i.e., they need not be removed during processing to yield a commercially salable oil. Such desirable components commonly include diglycerides, tocopherols, sterols, and sterol esters, and some oils will include other desirable components (e.g., tocotrienols in palm oil). Other compounds in the raw vegetable oil are undesirable impurities which can adversely affect the taste, smell, appearance, or storage stability of a refined oil and hence are beneficially removed. These undesirable impurities generally include phospholipids (also known as phosphatides), free fatty acids, odiferous volatiles, colorants, waxes, and various metal compounds. Some of these undesirable impurities (e.g., metal compounds) are contaminants which have little or no commercial value. Free fatty acids and some other components of raw oils are undesirable in a processed oil and maybe considered "undesirable impurities" in that context, but may still have meaningful commercial value.

[0004] As mentioned above, crude vegetable oil contains phosphorous compounds, mainly in the form of phospholipids. As used herein, the term "phospholipids" includes, but is not limited to, lyso-phospholipids which are products of hydrolysis of one of the fatty acid-glycerol bonds in phospholipids. Typically the phosphorous (P) content of crude oil is several hundreds of part per million (ppm), corresponding to phospholipids concentration of about 2-3% w/w. Crude oil also contains free fatty acids, typically at concentrations of up to 1% w/w. Refining of crude oil involves removal of phospholipids and free fatty acids. Phospholipids removal, which is also referred to as degumming, is typically conducted by contacting the crude oil with water, which hydrates the phospholipids to a form that is less soluble in oil. According to a first industrial practice, hydrated phospholipids are then separated by centrifugation to form degummed oil and a hydrated-phospholipids product, also referred to as "gums". The phosphorous content of the degummed oil is typically reduced by 80-90% compared with the crude oil. The gums could then be added to animal feed or further treated to form refined phospholipids also referred to as "lecithin." Typically, the degummed oil is then treated with a solution of an alkali, which converts free fatty acids in it into their alkali salt form, also referred to as soap. The soap is then separated from the alkali-treated oil, typically by centrifugation to form degummed alkali-treated oil and a soapstock. According to a second industrial practice, alkali treatment is combined with the water treatment, without first removal of gums or is conducted simultaneously with it. In those cases, a single centrifugation is applied, removing both the gums and the soap. These and other procedures related to oil refining are described in Bailey's Industrial Oil & Fat Products 5th Ed., edited by Y. H. Hui, Vol. 4.

[0005] Crude oil is relatively viscous and of relatively high density, which hinders separation of gums and soap. As a result, significant amounts of oil are lost into the gums and soap in processing according to the first practice and into the gums/soap composition according to the second process described above. (Here, and in the following, "oil losses" refer to losses of triglycerides, leading to lower yields on the triglycerides.) Crude oil diluted with a solvent is less viscous and of lower density, and as such is expected to have lower losses during degumming and alkali treatment. Using a solvent other than that of extraction is feasible, but adds a degree of complication and cost in having to deal with multiple solvents. For that reason, diluting in hexane is more attractive in cases where hexane is the extracting solvent. Furthermore, there is no need for hexane re-addition to the crude oil.

[0006] Extracting oilseeds with hexane generates a solution of hexane containing the oil (triglycerides), phospholipids, fatty acids and other components. A solution comprising those components is referred to here as oil miscella. Oil miscella could be a direct product of extraction or a result of some modification; e.g., removing part of the solvent via distillation. Oil miscella could also be a product of mixing a solvent solution formed in extraction of an oilseed with crude oil obtained by pressing the same oilseed or another oilseed. The oil miscella is less viscous and of lower density than the crude oil, and its refining therefore involves less oil losses. [0007] Cottonseed oil is miscella refined, but centrifugation is used for phase separation. Soybean oil miscella, though, typically is not directly refined. Typically, solvent (e.g., hexane) is fully removed from the oil miscella prior to any refining.

[0008] Accordingly, there is a need for an oil refining method that involves reduced loss of triglycerides. There is also a need for a method for refining oil that is of low cost and low risk

SUMMARY

[0009] Disclosed herein are several methods for refining oil, particularly refining of oil miscella derived from soybeans.

[0010] One example of such a method includes extracting an oilseed with at least one organic solvent to form oil miscella comprising at least one triglyceride, at least one organic solvent, at least one phospholipid, and at least one fatty acid; contacting the oil miscella with at least one of (i) water or (ii) an aqueous solution to form a medium having at least two immiscible phases, wherein at least a fraction of at least one of the immiscible phases is dispersed in the other immiscible phase; coalescing the dispersed immiscible phase; separating the immiscible phases to generate a separated lipophilic product comprising the at least one triglyceride and the at least one solvent and a separated hydrophilic coproduct comprising water, the at least one phospholipid, and the at least one fatty acid, wherein centrifugation is not used for the separating the immiscible phases; and treating the lipophilic product to generate refined oil. [0011] The method of another embodiment includes providing a feed stream comprising triglycerides, an organic solvent and hydratable lipids selected from the group consisting of phospholipids, soap and their combinations; and wherein said feed stream comprises at least one of (i) hydratable lipids dispersed in a phase comprising triglycerides, or (ii) triglycerides dispersed in a phase comprising hydratable lipids, and separating the hydratable lipids from the triglycerides by coalescing and a hydrocyclone to generate a product enriched with triglycerides and a coproduct enriched in hydratable lipids. [0012] According to a further embodiment, there is described a process that includes contacting an oil miscella with (1) an aqueous acid, (ii) an aqueous alkali, or (iii) both an aqueous acid and an aqueous alkali to form hydratable lipids dispersed in a miscella phase, which hydratable lipids are selected from the group consisting of phospholipids, soap and mixtures thereof, wherein the oil miscella comprises hexane, triglycerides, phospholipids and free fatty acids; coalescing the dispersed hydratable lipids to form a continuous medium comprising hydratable lipids and triglycerides; separating the continuous medium from the miscella phase to generate separated miscella and separated medium; and separating hydratable lipids from triglycerides in the separated medium by means of a hydrocyclone to generate a first stream enriched with triglyceride and a second stream enriched with hydratable lipids.

[0013] In a further embodiment, the method includes forming a medium comprising triglycerides, organic solvent, water and at least one hydratable lipid selected from the group consisting of phospholipids, fatty acid salts and mixtures thereof, wherein the weight ratio of triglycerides to hydratable lipid is less than about 5 to 1, which medium comprises at least two immiscible phases, wherein at least a fraction of at least one of the immiscible phases is dispersed in the other immiscible phase; coalescing said dispersed immiscible phase; and separating said immiscible phases to form a stream enriched with triglycerides and a stream enriched with hydratable lipid, which separating does not include centrifugation. [0014] The foregoing and other objects, features, and advantages will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a process flow diagram showing an example of a novel process that includes refining oil miscella (derived from high oil content oilseed) with residual soap removal via filtration.

[0016] Figure 2 is a process flow diagram showing another example of a novel process that includes refining oil miscella (derived from high oil content oilseed) with water wash of residual soap.

[0017] Figure 3 is a process flow diagram of an example of a novel process that includes refining oil miscella (derived from low oil content oilseed) with residual soap removal via filtration. [0018] Figure 4 is a process flow diagram of another example of a novel process that includes refining oil miscella (derived from low oil content oilseed) with a water wash column.

DETAILED DESCRIPTION

[0019] "Enriched" means having a concentration greater than that in the feed stream, when determined on the same basis, e.g. weight per weight or solvent-free basis. [0020] "Oil" refers to the portion of an oilseed that is removed from the oilseed via any type of extraction method such as mechanical pressing, steam extraction or solvent extraction. The oil portion typically includes triglycerides, diglycerides, tocopherols, sterols, sterol esters, phospholipids, free fatty acids, odiferous volatiles, colorants, waxes, and various metal compounds.

[0021] "Triglyceride" refers to a derivative of glycerol in which all three available hydroxyl groups are esterified with fatty acids. Depending on the oil source, these triglycerides may include a variety of saturated, partially saturated, and unsaturated fatty acids (e.g., oleic, linoleic, linolenic, lauric, palmitic, and myristic acids) esterified on a glycerol molecule in various combinations.

[0022] The above term descriptions are provided solely to aid the reader, and should not be construed to have a scope less than that understood by a person of ordinary skill in the art or as limiting the scope of the appended claims.

[0023] The singular terms "a," "an," and "the" include plural referents unless context clearly indicates otherwise. Similarly, the word "or" is intended to include "and" unless the context clearly indicates otherwise. The word "comprises" indicates "includes." The various combinations described below are illustrative; any and all combinations of ingredients, components, and/or numerical values of ranges are included within the present disclosure. [0024] Refining of oil miscella has two inherent difficulties. The first is related to degumming yield. Degumming oil miscella by contacting with water (referred to in the following as water degumming) is in many cases less efficient (see the results in comparative example 1 below) leading to too high residual phosphorous content in the degummed miscella. The cause may be that phospholipids solubility improves in the presence of hexane and/or hydration is less efficient. Another difficulty is related to the presence of hexane in the miscella, which requires high-cost, explosion-proof centrifuges for the separation of the gums and the soaps. [0025] It has been surprisingly found that refining oil miscella according to the method described herein provides several advantages. Refining of the oil miscella according to these methods is efficient and lowers phosphorous concentrations to ones similar to those in degumming/refining crude oil. The gums and soaps are generated in a form that is easy to separate from the oil miscella, so that centrifugation is not necessary. Oil losses are considerably reduced compared with those in refining crude oil in presently used practice. The presently disclosed miscella refining methods increase oil yields compared with conventional refining methods by minimizing oil losses into co-product streams, such as gums, soapstock and streams containing both gums and soap. In addition, the present methods save energy, minimize effluent treatment, save on bleaching clay consumption and on maintenance cost.

[0026] In one embodiment, the oil refining process includes extracting an oilseed with an organic solvent to form oil miscella comprising triglyceride(s), solvent(s), phospholipid(s) and fatty acid(s). Any oilseed is suitable for the present process such as, for example, soybean, canola, sunflower, cotton, palm kernel, corn, rapeseed, sesame, peanut and mixtures thereof. According to a preferred embodiment, the oilseed is soybean. An optional pre-extraction mechanical pressing step may be employed to remove an initial fraction of oil. The oilseeds may also be subjected to cleaning and dehulling prior to extraction.

[0027] Any organic solvent capable of extracting oil is suitable. For example, the solvent may be an aliphatic or alicyclic hydrocarbon such as hexane. As used herein, "hexane" refers to a pure hexane isomer (e.g., n-hexane) or a mixture of C₆ aliphatic and/or alicyclic hydrocarbons, particularly n-hexane, isohexane and/or methylcyclopentane. Other illustrative solvents include low molecular weight alcohols, such as ethanol and isopropyl alcohol; aromatic hydrocarbons such as benzene, toluene and xylene; halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, trichloro ethylene, and dichloroethane; ketones such as acetone and methyl ethyl ketone; ethers such as diethyl ether; and esters such as ethyl acetate. [0028] The extracting may occur at suitable processing conditions for obtaining the desired amount of extracted oil. The processing conditions (temperature, time, pressure, etc.) will vary depending upon the type of oilseed and extraction solvent. For example, in general, extraction may occur at a temperature of about 5 to about 95, particularly about 20 to about 60, ⁰C, at a pressure of about 0.1 to about 10 atm, particularly about 1 arm. The amount of solvent mixed with the oilseed may vary depending upon the type of solvent and oilseed. Countercurrent extraction (which may be multistage continuous) and/or crosscurrent extraction (which may be batch) may be used. For example, the extractor uses solvent for mixing with the oilseed that ranges from oil-free solvent to solvent containing up to about 35-40 wt% oil. For instance, in a multistage countercurrent extraction, the first stage may use as the solvent a 35% oil-in hexane mixture, and the last stage may use oil-free solvent.

[0029] In one embodiment, the oil miscella could be the product of extracting an oilseed with a selected solvent; the oil miscella comprising triglyceride(s), solvent, phospholipids and fatty acids. However, the composition of that extraction product could be modified, for example, to adjust the concentration of triglycerides in it. In a typical product of extracting soybeans with hexane, triglycerides concentration is about 20% w/w. According to a preferred embodiment of the presently disclosed processes, the triglyceride concentration in the oil miscella (prior to refining with water or an aqueous solution as describe herein) is at least 40% w/w, more preferably at least 50% w/w, most preferably at least 70% w/w. In one example, the oil miscella has a triglyceride concentration of about 50 to about 70% w/w.

[0030J According to one approach, the triglyceride concentration in the oil miscella may be increased by at least partial solvent removal (e.g., distillation of hexane) prior to refining of the oil miscella. According to another approach, modifying the triglyceride concentration in the oil miscella is done by mixing the extraction product with crude oil, as further described below. The common industrial practice for oil extraction from oilseeds containing more than 20% oil, involves two steps. In the first, part of the oil is mechanically separated from the oilseed, e.g. by pressing. In the second step, the rest of the oil is extracted with hexane to form a miscella. The concentration of the oil in the miscella is increased, according to one embodiment, by mixing with mechanically separated oil. According to still another embodiment, oil concentration in the miscella is adjusted by a combination of adding crude oil and distilling out part of the solvent. Thus, the triglyceride concentration in the miscella may be adjusted between the various stages, e.g. by removing solvent or by adding oil or miscella with higher oil concentrations. The miscella, minus the oil fraction, can include up to almost 100% solvent, hi certain embodiments, the solvent concentration in the oil miscella may range from about 10 to about 60% w/w, preferably from about 20 to about 50% w/w. In certain embodiments, the fatty acid(s) concentration in the oil miscella may range from about 0.1 to about 2% w/w, more preferably about 0.5 to about 1.5% w/w. The certain embodiments, the phospholipid(s) concentration in the oil miscella may range from about 0.3 to about 5% w/w, preferably from about 1 to about 4% w/w.

[003 IJ The oil miscella is treated to remove phospholipids and fatty acids contained in it. Each one of those, products of their modification (e.g. salts of fatty acids and partially hydrolyzed phospholipids, such as lyso-phospholipids) and their combinations are also referred to herein as "hydratable lipids." According to an embodiment of the process, phospholipids are removed first by contacting the miscella with water, optionally containing an acid such as phosphoric or citric, to form a coproduct also referred to as "gums," which can then be separated without using any centrifugation. Then the miscella is contacted with an aqueous solution of a base to remove fatty acids as their salt (typically sodium salt) and to form a coproduct also referred to as "soap" or "soapstock," which can then be separated without using any centrifugation. According to another embodiment, the miscella is initially contacted with an aqueous solution of a base, whereby both phospholipids and fatty acids are removed. These embodiments are further described in the following.

[0032] According to certain embodiments, contacting with at least one of water, aqueous solution, acid solution and/or alkali solution involves strong mixing, using suitable means. Mixing duration may be in the range between about 5 minutes and about 300 minutes, more preferably between about 20 minutes and 200 minutes. Preferably, the water to miscella weight ratio is in the range between about 0.001 and about 0.5, more preferably between about 0.01 and about 0.1. According to a preferred embodiment, contacting is conducted at an elevated temperature, but preferably below the boiling point of the solvent (e.g., hexane). According to a preferred embodiment, contacting the miscella with the aqueous phase and/or the alkaline solution is conducted at a temperature in a range between 20⁰C and 60⁰C, preferably between 30°C and 5O⁰C. Illustrative aqueous acid solutions include phosphoric and citric. [0033] Since water has low miscibility with oil and with miscella, said contacting of miscella with water, alkaline solution or both, forms a medium or composition with at least two immiscible phases. One of those phases, also referred to here as the lipophilic phase, consists mainly of triglycerides and solvent, while the other, the hydrophilic phase, consists mainly of water, phospholipids and/or fatty acid salts. For example, the lipophilic phase may include at least about 80%, preferably at least about 95%, w/w triglycerides and solvent combined. Similarly, for example, the hydrophilic phase may include at least about 80%, preferably at least about 95%, w/w water, phospholipids and fatty acid salts combined.

[0034] Complete separation between these two immiscible phases is difficult since at least a fraction of at least one of those is dispersed in the other. Thus, one may find microphases, e.g. droplets, of the hydrophilic phase dispersed in a continuous lipophilic phase and/or microphases of the lipophilic phase dispersed in a continuous hydrophilic phase. Incomplete separation leads to inefficient refining and/or losses of triglycerides. Completely separating the two phases by settling and decantation would require too much time for an industrial practice. There is the option of separating the phases by means of centrifugation, but it is not desired. The main reason for that is the presence of solvent in the medium, which would require an explosion-proof unit, which drastically increases the cost of the equipment. The presently described methods surprisingly provide an avenue for separating the phases without resorting to centrifuges. It was found that a coalescing operation enables minimizing or eliminating the dispersion. Coalescing involves droplet growth as small drops merge together when they come into contact. Hence, the phases can be separated by means other than centrifugation. For example, the phases can be separated by decantation, separation columns and/or hydrocyclones. Particularly preferred is phase separation by means of hydrocyclones.

[0035] According to one embodiment, the contacting of the water and/or aqueous solution with the oil miscella is conducted in the presence of a solid component. It has been presently found that the presence of a solid component improves subsequent phase separation, possibly by facilitating coalescing. Preferably, illustrative solid components include solids with large surface area (e.g., fuller's earth, diatomaceous earth, clay, wood pulp), filter aids, and solid components of animal feed and solids acceptable in animal feed. Examples for suitable solid components of animal feed are soy hulls and soybean meal.

[0036] As described above, phase separation generates at least two phases. One of those is a separated hydrophilic coproduct that includes water and at least one other component selected from phospholipids and fatty acid salts. The hydrophilic coproduct may also contain some triglyceride. Phase separation also forms a lipophilic product comprising triglycerides and solvent. The lipophilic product may also contain residual amounts of hydratable lipids and some other impurities. In certain instances, the lipophilic product includes about 10 to about 90, more particularly about 40 to about 80, % w/w triglycerides, and about 10 to about 90, more particularly about 20 to about 60 % w/w solvent.

[0037] The lipophilic product is further treated to form refined oil. This further refining treatment removes solvent as well as cloudiness, excess color, unpleasant flavors, and other undesirable components. Typically, said treatment involves removal of solvent by known methods, such as distillation, bleaching and deodorization according to known methods. Other treatments, such as enzymatic ones may also be used to treat the lipophilic product prior to, or after, solvent removal. Bleaching may improve the color and flavor of refined oil by decomposing peroxides and removing oxidation products, trace phospholipids, and trace soaps. In the final physical refining and/or deodorizing step, remaining volatilizable impurities are removed to yield a deodorized vegetable oil having the desired final characteristics. The volatilizable impurities removed in the deodorization process commonly include free fatty acids, aldehydes, ketones, alcohols, and other hydrocarbon impurities. Some of these impurities may come directly from the oil seeds themselves while others may arise from pesticides, fungicides, and other compounds applied to the seeds or to the plants from which the seeds are derived. [0038] The resulting refined oil is of a quality at least as high as commercial refined oil produced by other methods, as determined by specifications such as the concentration of phosphorous and fatty acid. Thus, according to a preferred embodiment, the concentration of P in the initial oil miscella is at least about 200 ppm, more particularly at least about 400 ppm, as calculated on the amount of the contained triglycerides. According to related preferred embodiments, the concentration of P in the separated lipophilic phase is less than 60 ppm, more particularly less than about 30 ppm, and/or that in the refined oil is less than 10 ppm, more particularly less than about 3 ppm, calculated on the same basis. In other embodiments, the concentration of P in the refined oil is less than 150 ppm, more particularly less than about 50 ppm, calculated on the amount of triglycerides contained in the refined oil. According to certain embodiments, the concentration of fatty acid in the refined oil is less than about 0.1%, particularly less than about 0.05%, preferably less than about 0.03%, w/w.

[0039] Another characteristic of embodiments of the process is reduced losses of triglycerides to the coproduct stream compared to the losses in current industrial practice. For example, the hydrophilic phase may include less than 1%, preferably less than 0.5%, w/w of the triglyceride amount initially present in the oil miscella.

[0040] According to certain embodiments, the process comprises multiple separation steps, multiple coalescing steps or both. Those steps could be operated in any order. For example, the miscella is contacted with water and/or an alkali solution to form a system with two immiscible phases and dispersed microphases as described above. A first separation step is applied to generate a first separated lipophilic phase and a first separated hydrophilic phase. At least one of those separated phases has microphases of the other phase dispersed in it. Thus, the first separated lipophilic phase has hydrophilic phase dispersed in it and/or the first separated hydrophilic phase has dispersed lipophilic phase dispersed in it. According to one approach, at least one of these first separated phases is treated for coalescing followed by a second phase separation. For example, the first separated hydrophilic phase comprises dispersed lipophilic phase comprising triglycerides and solvent. It is treated for coalescing followed by phase separation, whereby a second separated hydrophilic phase is formed, with less triglycerides and solvent compared to the first hydrophilic phase. Also separated is a second lipophilic phase, comprising mainly triglycerides and solvent. That second lipophilic phase is low in hydratable lipids and suitable for combining with streams such as the first lipophilic phase and the separated lipophilic product, reducing thereby the losses of triglycerides to hydrophilic coproducts. [0041] According to a preferred embodiment, oil is refined in a process comprising the steps of providing oil miscella comprising hexane, triglycerides, phospholipids and free fatty acids; contacting said miscella with at least one of water, acidic water and/or alkaline solution to form microphases of hydratable lipids in a continuous miscella phase; coalescing at least part of said microphases to a continuous hydratables medium, which medium comprises hydratable lipids, hexane and triglycerides; separating said continuous hydratables medium from said continuous miscella phase to form separated miscella and separated hydratables medium; and separating hydratable lipids from triglycerides in said medium by means of hydrocyclone to generate a first stream enriched with triglyceride and a second stream enriched with hydrated phospholipids. [0042] hi another illustrative embodiment, there is provided a method for the refining of oil that includes providing a feed stream comprising triglycerides, an organic solvent and hydratable lipids selected from a group consisting of phospholipids, soap and their combinations; and wherein said feed stream comprises at least one of (i) hydratable lipids dispersed in a phase comprising triglycerides, or (ii) triglycerides dispersed in a phase comprising hydratable lipids, and separating hydratable lipids from triglycerides by means of coalescing and phase separation, e.g. by means of hydrocyclone to generate a product enriched with triglycerides and a coproduct enriched in hydratable lipids and optionally also triglycerides, and optionally treating said product to generate refined oil. Treatment of said triglyceride-enriched product and the purity of the formed refined oil are similar to those described above. Here again no centrifugation is used for phase separation.

[0043] According to a further preferred embodiment, the method includes providing oil miscella comprising hexane, triglycerides, phospholipids and free fatty acids; at least one of (i) contacting said miscella with water and with an acid selected from a group consisting of phosphoric acid, citric acid and their combinations and (ii) contacting said miscella with at least one of water and alkali, forming hydratables lipids dispersed in a miscella phase, which hydratable lipids are selected from a group consisting of phospholipids, soap and their combinations ; coalescing said dispersed hydratable lipids to a medium comprising hydratable lipids and triglycerides; separating said medium from said miscella to form separated miscella and separated medium; and separating hydratable lipids from triglycerides in said medium by means of hydrocyclone to generate a first stream enriched with triglyceride and a second stream enriched with hydratable lipids and optionally combining said first stream with said separated miscella. [0044] According to another preferred embodiment, in cases wherein, separated miscella, treated separated miscella or any other stream enriched with triglycerides comprises hydratable lipids, those hydratable lipids are separated by means of at least one of filtration, adsorption and washing or a combination of those. According to a preferred embodiment, filtration/adsorption uses a filter aid, such as diatomaceous earth. According to another preferred embodiment, washing uses water recycled from the extraction process.

[0045] Also disclosed is a method for refining oil comprising the steps of forming a medium comprising triglycerides, organic solvent, water and at least one hydratable lipid selected from a group consisting of phospholipids, fatty acid salts and their combination, wherein the weight ratio between triglycerides and hydratable lipid is less than about 5 to 1, which medium comprises at least two immiscible phase, wherein at least a fraction of at least one of said immiscible phase is dispersed in the other immiscible phase; coalescing said dispersed immiscible phase; and separating said immiscible phases to form a stream enriched with triglycerides and a stream enriched with hydratable, which separating does not use centrifugation. According to a preferred embodiment, the medium is formed from coproducts of conventional oil refining method, i.e. gums and or soapstock, which contain entrained triglycerides. Formation of the medium involves combining the coproduct with solvent, e.g. by mixing with a solvent or with a miscella formed on extraction of an oilseed with a solvent or with partially desolventized oil miscella.

[0046] If desired, phosphorous concentration in at least one of the lipophilic, phospholipids- containing streams generated in the process is further reduced, preferably in a treatment that involves reaction with water. According to a preferred embodiment, the treatment comprises reaction with water for hydrolysis of phospholipids, their degradation products or a combination of those. According to a preferred embodiment, hydrolysis removes at least one of the fatty acids bound to the phospholipid's glycerol backbone via an ester bond. According to a preferred embodiment, hydrolysis is catalyzed chemically, enzymatically or via a combination of those. Particularly preferred is enzymatic catalysis using phospholipid-hydrolyzing enzymes. Preferred enzymes are ones specific to hydrolyzing ester bonds of fatty acids on phospholipids, with minimal triglyceride-hydrolyzing activity. Suitable enzymes include Lecitase Ultra, phospholipase Al, phospholipase A2 (Novozyme), phospholipase C (Verennium), phospholipase D {Novozyme), and mixtures thereof. The amount of enzyme, reaction duration and reaction temperature are adjusted based on the phosphorous concentration in the miscella, on enzyme activity and on the preferred conditions for the enzyme. According to a preferred embodiment, the reaction with water leads to low-P streams with phosphorous concentration of less than about 20 ppm of the oil content, more preferably less than 10 ppm, most preferably less than 5 ppm. [0047] Preferred embodiments of the methods are described in the following with references to Figures 1-4.

[0048] Figures 1 and 2 present preferred embodiments wherein the miscella is derived from an oilseed with relatively high oil content (e.g., at least about 20 % w/w oil). A fraction of the oil in the oilseed is separated by mechanical means, while the rest is extracted with a solvent, such as hexane. The extraction generates an oil miscella, which is a solution of triglycerides (about 25% w/w), phospholipids and free fatty acid in the extraction solvent. The miscella (denoted in Figures 1 and 2 as extraction full miscella) is mixed in a miscella tank with the mechanically extracted oil (denoted "prep oil from decanters") and with concentrated phosphoric acid in an amount that is about 0.1% w/w of the oil. The oil concentration in the solution formed in the miscella tank is about 50% w/w, and could be further increased by distilling part of the hexane. The mixture is then mixed in a caustic mixer with a solution of about 10% NaOH. The amount of the base is calculated to be about 1.2 moles per mole of free fatty acids in the mixture. The alkali-treated miscella contains microphases of hydratable lipids - mainly gums and soap - in a continuous miscella phase composed mainly of triglycerides and solvent. According to the embodiment of Figures 1 and 2, the alkali-treated miscella is introduced along with an optional recycle stream (miscella recycle) into a coalescor, where hydratable-lipids microphases are coalesced to form a continuous hydratable phase, which is of higher density than the miscella phase. The coalescor may be a closed vessel with one liquid inlet, two liquid outlets, and a vapor vent. Coalescing may also occur in pipes or conduits between the caustic mixer and the separating column. The miscella may be subjected to an energy input (e.g., ultrasonic energy) prior to its introduction into the coalescor unit and/or while it is present in the coalescor unit. For example, the miscella (mixed with aqueous component) in the coalescor unit (e.g., via a sonic splitter commercially available from Etrema Co.) can be subjected to low frequency sound waves (e.g., 600 — 1600 Hz) to accelerate coalescence of water and oil particles. In one embodiment, the frequency is 1120 Hz at a flow arate ranging from 56-76 L/min. [0049] The two phases are separated in a separating column. The separating column may include two outlets, one for each of the two liquid phases to be separated. They may be located at the top and bottom, respectively, of a vertical cylindrical vessel, or they may be standpipes or weirs in a vessel of a different shape. The heavy phase contains gums, soap and occluded miscella (triglycerides in solvent). That heavy phase is treated in a heavy phase hydrocyclone, which facilitates phase separation. The separated hydratable lipids (gums and soap) are sent, according to the embodiment of Figures 1 and 2, to a desolventizer-toaster ("DT") where it is mixed with the soybean meal from the extraction. The separated miscella (denoted miscella recycle) is combined with the miscella, preferably after alkali treatment, so that the triglycerides separated in the hydrocyclone end up with the light phase separated from the separating column. [0050] Figures 1 and 2 present two different embodiment of treating the light phase separated from the separating column. That phase may contain residual hydratable lipids. According to the embodiment of Figure 1, those lipids are separated by filtration with a filter aid, such as diatomaceous earth ("DE") in the DE filter. A refined miscella is formed and sent to distillation in order to remove the solvent. The spent DE is preferably sent to an extractor for reclamation. According to the embodiment of Figure 2, the miscella phase out of the separating column is washed with water in a washing column to generate the refined miscella for distillation. The water is preferably obtained from a solvent water separator (not shown) and the aqueous stream out of the washing column (wash water) is preferably sent to a re-boiler.

[0051] Figures 3 and 4 present process schemes of preferred embodiments where oil is extracted from an oilseed with a relatively low oil content (e.g., less than about 20% w/w), such as soybean. In such cases there is typically no mechanical extraction of oil and the oil is solvent extracted from the oilseed, forming a miscella of oil, phospholipids and free fatty acids in the solvent. In most cases, the oil concentration in the miscella is too low for treatment. Solvent (hexane in most cases) is distilled in an amount that increases the concentration of the oil in the remaining miscella to about 50% or higher (about 25% of the initial extracting solvent remains after this partial distillation). Hexane distillation in the processes of Figures 3 and 4 is conducted after contacting with phosphoric acid. The reverse order (hexane distillation followed by phosphoric acid) is also feasible. From this point on, the processes of Figures 3 and 4 are similar to those of Figures 1 and 2, respectively.

[0052] The presently disclosed miscella-refining methods increase oil yields compared with the conventional refining methods by minimizing oil losses into coproduct streams, such as gums, soapstock and ones containing both gums and soap. In addition they save on energy, on effluent treatment, on bleaching clay consumption and on maintenance cost. Examples

[0053] The miscella samples tested were prepared by partial distillation of hexane from miscella formed in an industrial soybean oil extraction plant operated according to a typical industrial practice. On solvent-free basis, the concentration of phosphorous (P) in the form of phospholipids and the concentration of free fatty acids were 550 parts-per-million (PPM) and 0.54%, respectively. Miscella samples of various oil concentrations were prepared by adjusting the hexane concentration via distillation.

Example 1

[0054] In the first stage, samples of miscella adjusted to 30% w/w oil were mixed with water at miscella/water w/w ratio of 250/1 or 25/1. The P concentration in the oil miscella was about 170 ppm (550 ppm on a solvent-free basis). Mixing temperature and duration were 25°C and 30 minutes, respectively. At the end of mixing, the mixtures were allowed to settle. Phase separation was good. In the second stage, 50% NaOH was added at about 1.5% of the miscella weight. Mixing was continued for additional 30 minutes at the same temperature, after which the mixtures were allowed to settle. Phase separation was good. Samples of the organic (lighter) phase were analyzed. The fatty acid content was below titration-based detection limit. P concentration on a solvent-free basis was 300-400ppm, depending on the amount of water added and the intensity of mixing.

Example 2

[0055] The procedure in the first step of Example 1 was repeated, except that the oil concentration in the miscella was adjusted to 70% w/w and the mixing temperature was 4O⁰C in some of the cases (25°C in some others). The P concentration in oil miscella was about 390 ppm. Phase separation was still good. P concentrations on a solvent-free basis were 100-

200ppm.

Example 3

[0056] The procedure of Example 1 was repeated, except that the oil concentration in the miscella was adjusted to 70% w/w. In some of the cases mixing was vigorous. Phase separation was good in all cases and fatty acids were not detected. P concentrations were similar to those in Example 2. Samples produced in tests where stronger mixing was applied had lower P concentration than the others. Example 4

[0057] The procedure of Example 3 was repeated with miscella samples where oil concentration was adjusted to 70, 80 or 90%. Miscella/water ratio was 25/1. Mixing time was varied between

30 and 120 minutes. No fatty acids were detected. P concentrations on a solvent-free basis were

45-60ppm.

Example 5

[0058] The procedure in of Example 3 was repeated, except that fuller's earth as a coalescing agent was added along with the water in the first stage. The fuller's earth improved both phase separation and phospholipids removal.

Example 6

[0059] A 70% oil miscella was mixed with water for 60 minutes at miscella/water ratio of about 35/1 and at 25°C. Treated miscella samples were then mixed with preparations of the enzyme Lecitase Ultra obtained from Novo. The preparations had about 13% of enzyme in acetate buffer (0.05M acetic acid 0.01M CaC12 pBN4.8). Between 0.19 and 0.38mg enzyme were used per gram of oil in the treated miscella. Mixing was conducted at 44⁰C for 5.5 hr. Then, the miscella samples were analyzed for the concentration of free fatty acid. 50% NaOH solution was added to reach NaOH/fatty acid molar ratio of 1.2. Mixing was applied at 25⁰C for 30min. At the end of the mixing, good phase separation was observed. The formed miscella samples were analyzed for free fatty acids and for P content. The results were 0.04-0.05% free fatty acid and 3-5ppm P, on solvent-free basis.

[0060] In view of the many possible embodiments to which the principles of the disclosed methods may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope of the invention.

Claims

What is claimed is:

1. A method for refining oil, comprising: extracting an oilseed with at least one organic solvent to form oil miscella comprising at least one triglyceride, at least one organic solvent, at least one phospholipid, and at least one fatty acid or salt thereof; contacting the oil miscella with at least one of (i) water or (ii) an aqueous solution to form a medium having at least two immiscible phases, wherein at least a fraction of at least one of the immiscible phases is dispersed in the other immiscible phase; coalescing the dispersed immiscible phase; separating the immiscible phases to generate a separated lipophilic product comprising the at least one triglyceride and the at least one solvent and a separated hydrophilic coproduct comprising water, the at least one phospholipid, and the at least one fatty acid or salt thereof, wherein centrifugation is not used for the separating the immiscible phases; and treating the lipophilic product to generate refined oil.

2. The method of claim 1 , wherein the refined oil has a phosphorus concentration of less than about 150 ppm, calculated on the basis of the triglyceride(s) contained in the refined oil.

3. The method of claim 1 , wherein the refined oil has a phosphorus concentration of less than about 10 ppm, calculated on the basis of the triglyceride(s) contained in the refined oil.

4. The method of any one of claims 1-3, wherein the refined oil has a fatty acid concentration of less than about 0.1% w/w.

5. The method of any one of claims 1-4, wherein the hydrophilic coproduct further comprises at least one triglyceride, wherein the triglyceride in the coproduct constitutes less than about 1% w/w percent of the triglyceride in the oil miscella.

6. The method of any one of claims 1 -5, wherein the medium comprises a hydrophilic phase dispersed in a lipophilic phase.

7. The method of any one of claims 1-5, wherein the medium comprises a lipophilic phase dispersed in a hydrophilic phase.

8. The method of any one of claims 1-7, wherein the medium having at least two immiscible phases is introduced into a coalescor unit.

9. The method of claim 8, wherein the medium having at least two immiscible phases is subjected to an energy input prior to introduction into the coalescor unit or when the medium is in the coalescor unit.

10. The method of claim 9, wherein the energy input is in the form of ultrasonic energy.

11. The method of any of claims 1-10, wherein the medium having at least two immiscible phases is contacted with at least one coalescing agent.

12. The method of any of claims 1-11, wherein the coalescing of the dispersed immiscible phase results in a coalesced immiscible phase, and the separating of the immiscible phases includes introducing the medium including the coalesced immiscible phase into a hydrocyclone to separate the immiscible phases.

13. The method of any of claims 1-12, wherein the contacting is with an aqueous acid solution and the coproduct comprises hydrated phospholipids.

14. The method of any of claims 1-12, wherein the contacting is with an aqueous alkali solution and the coproduct comprises fatty acid salts.

15. The method of claim 1, further comprising: an initial separation of the two immiscible phases prior to coalescing, wherein at least a fraction of at least one of the immiscible phases remains dispersed in the other immiscible phase; and then subjecting at least one of the separated phases to the coalescing.

16. The method of any of claims 1-11, wherein the contacting is with an aqueous acid and with an aqueous base.

17. The method of claim 16, further comprising an initial separation of the two immiscible phases between contacting with the aqueous acid and contacting with the aqueous base.

18. The method of any of claims 1-17, wherein the separated hydrophilic coproduct comprises dispersed triglycerides, and further comprising coalescing the dispersed triglycerides and phase separating to produce separated triglycerides.

19. The method of any of claims 1-18, further comprising treating at least one of the oil miscella, medium or separated phase with at least one phospholipid- hydrolyzing enzyme to hydrolyze phospholipids contained in the oil miscella, medium, or separated phase.

20. The method of any of claims 1-19, wherein the triglyceride concentration in the oil miscella is at least about 40% w/w.

21. The method of any of claims 1-19, wherein the triglyceride concentration in the oil miscella is at least about 70% w/w.

22 The method of any of claims 1-11, wherein phosphorus concentration in the oil miscella is at least about 200ppm of the triglyceride content.

23. The method of any of claims 1 -22, wherein phosphorus concentration in the separated lipophilic product is less than about 60 ppm of the triglyceride content.

24. The method of any of claims 1 -23, wherein phosphorus concentration in the separated lipophilic product is less than about 10 ppm of the triglyceride content.

25. The method of claim 1, wherein the contacting is conducted at a temperature in the range between 2O⁰C and 60°C.

26. The method of any of claims 1-10, 12-25, wherein the contacting occurs in the presence of a solid medium.

27. The method of claim 26, wherein the solid media is a solid with large surface area, a filter aid, a solid component of animal feed, a solid acceptable in animal feed, or a mixture thereof.

28. The method of any of claims 1 -27, wherein the oilseed is soybean.

29. The method of any of claims 1-28, wherein the organic solvent is hexane.

30. A method of refining oil, comprising: providing a feed stream comprising triglycerides, an organic solvent and hydratable lipids selected from the group consisting of phospholipids, soap and their combinations; and wherein said feed stream comprises at least one of (i) hydratable lipids dispersed in a phase comprising triglycerides, or (ii) triglycerides dispersed in a phase comprising hydratable lipids, and separating the hydratable lipids from the triglycerides by coalescing and at least one hydrocyclone to generate a product enriched with triglycerides and a coproduct enriched in hydratable lipids.

31. The method of claim 30, wherein the separating does not include centrifugation.

32. The method of claim 30, wherein the separating comprises introducing the feed stream into a coalescor unit and a separating column.

33. A method for refining oil, comprising: contacting an oil miscella with at least one of (i) water, (ii) an aqueous acid, and/or (iii) an aqueous alkali to form hydratable lipids dispersed in a miscella phase, which hydratable lipids are selected from the group consisting of phospholipids, soap and mixtures thereof, wherein the oil miscella comprises hexane, triglycerides, phospholipids and free fatty acids; coalescing the dispersed hydratable lipids to form a continuous medium comprising hydratable lipids and triglycerides; separating the continuous medium from the miscella phase to generate separated miscella and separated medium; and separating hydratable lipids from triglycerides in the separated medium via a hydrocyclone to generate a first stream enriched with triglyceride and a second stream enriched with hydratable lipids.

34. The method of claim 33, wherein the separated miscella comprises hydratable lipids, further comprising separating the hydratable lipids by at least one of filtration, adsorption and washing to generate refined miscella.

35. The method of claim 33 or 34, wherein the triglyceride concentration in the oil miscella is at least about 70% w/w.

36. The method of claim 35, wherein phosphorus concentration in the oil miscella is at least about 200ppm of the triglyceride content, and phosphorus concentration in the refined miscella is less than about 10 ppm of the triglyceride content.

37. The method of claim 34, further comprising removing solvent from the refined miscella.

38. The method of any of claims 33-37, wherein the contacting occurs in the presence of a solid media.

39. A method for refining oil, comprising: forming a medium comprising triglycerides, organic solvent, water and at least one hydratable lipid selected from the group consisting of phospholipids, fatty acid salts and mixtures thereof, wherein the weight ratio of triglycerides to hydratable lipid is less than about 5 to 1, which medium comprises at least two immiscible phases, wherein at least a fraction of at least one of the immiscible phases is dispersed in the other immiscible phase; coalescing said dispersed immiscible phase; and separating said immiscible phases to form a stream enriched with triglycerides and a stream enriched with hydratable lipid, which separating does not include centrifugation.