WO2016189333A1

WO2016189333A1 - A process for refining glyceride oil comprising a basic ionic liquid treatment

Info

Publication number: WO2016189333A1
Application number: PCT/GB2016/051566
Authority: WO
Inventors: Peter Goodrich; Eoghain O'HARA; Martin Philip Atkins; Christopher Klatt HAMER
Original assignee: Queens University of Belfast
Current assignee: Queens University of Belfast
Priority date: 2015-05-27
Filing date: 2016-05-27
Publication date: 2016-12-01
Anticipated expiration: 2017-11-27
Also published as: GB2538756A; JP2018517038A; GB201509084D0; PH12017502157A1; CN108026476A; AR104799A1

Abstract

The present invention relates to an improved process for refining glyceride oil which incorporates a basic ionic liquid treatment. In particular, the basic ionic liquid treatment prevents or reduces the formation of chloropropanol fatty acid esters and glycidyl fatty acid esters during the overall refining process. The present invention also relates to glyceride oil compositions formed therefrom and uses of the basic ionic liquid.

Description

A PROCESS FOR REFINING GLYCERIDE OIL COMPRISING A BASIC IONIC

LIQUID TREATMENT The present invention relates to an improved process for refining glyceride oil which incorporates a basic ionic liquid treatment. In particular, the basic ionic liquid treatment prevents or reduces the formation of chloropropanol fatty acid esters and glycidyl fatty acid esters during the overall refining process. The present invention also relates to glyceride oil compositions formed therefrom and uses of the basic ionic liquid.

Crude glyceride oils extracted from natural sources typically undergo a variety of refining processes in order to remove unwanted contaminants and improve the organoleptic properties of the oil or other quality parameters depending on the intended use. Glyceride oil refining has in recent years come under increased scrutiny where the oil is intended for human consumption since it has been established that the nature of the refining process and even different cooking practices can lead to the formation of potentially carcinogenic or toxic contaminants. Two groups of known glyceride oil contaminants that have been identified as harmful to human health are chloropropanols and glycidol.

Fatty acid esters of chloropropanols and glycidol have been found to accumulate in glyceride oil, particularly refined oil which has been exposed to high temperatures during the refining process. Upon consumption, fatty acid esters of chloropropanols and glycidol are hydrolysed by lipases in the gastrointestinal tract, releasing free chloropropanols and glycidol. Non-esterified chloropropanols can also be present in glyceride oil, including monochloropropandiols, 2-chloro-1 ,3-propanediol (2-MCPD) and 3-chloro-1 ,2-propanediol (3-MCPD), or the corresponding dichloropropanols, 2,3-dichloropropan-1 -ol (2,3-DCP) and 1 ,3-dichloropropan-2-ol (1 ,3-DCP). 3-MCPD has been shown to exhibit in vitro genotoxic carcinogenic effects and a tolerable daily intake (TDI) of 2 g/Kg has now been established across the food industry. Exposure to 3-MCPD in vivo is thought to be possible from enzymatic hydrolysis of a variety of different chloropropanol fatty acid esters in the human Gl tract. Fatty acid esters of chloropropanols are produced from mono- or di-glyceride components of glyceride oil via acid promoted formation of a cyclic acyloxonium ion followed by ring opening with chloride. Meanwhile, fatty acid esters of glycidol are formed via the same cyclic acyloxonium ion implicated in the formation of chloropropanol fatty acid, except the acyloxonium ion is deprotonated giving rise to epoxide formation.

Although it has been established that traces of chloropropanols and glycidol, or their fatty acid esters, may be present in some native, crude glyceride oils, it is now understood that the refining process contributes significantly to their formation. In particular, heat exposure during deodorisation of glyceride oil, typically with steam stripping at a temperature of above 220 °C, has been found to be the predominant cause of chloropropanol/glycidol fatty acid ester formation in glyceride oil, whilst bleaching and degumming steps have also been found to contribute. Heat exposure promotes glycidol fatty acid ester formation whilst also causing thermal decomposition of organic chlorine-containing compounds, which in turn provides the necessary source of chloride for formation of chloropropanols.

Refining of crude lipid-containing glyceride oils typically comprises degumming, bleaching and deodorization, normally with a deacidification step included in the form of either neutralisation with strong base or an extended deodorization to remove any free fatty acids (FFA) present in the oil. Degumming typically involves addition of aqueous acid (citric and/or phosphoric acid) and may also remove other components of the glyceride oil, such as metal ions, at the same time as lipid components. Meanwhile, bleaching with bleaching earth not only reduces the amount of pigments it also absorbs other components of the oil, which can improve organoleptic properties.

Historically, glyceride oils have been treated with polar solvents as part of liquid- liquid extractions for separating glycerides according to their level of saturation or chain length, as well as for separating mono- and di-glycerides, FFA and glycerol, from triglycerides. Liquid-liquid extractions, such as alcohol extractions, are also known as a means for removing polar impurities from glyceride oils. However, such extractions may not be adequate for removing fatty acid esters of chloropropanols and glycidols which are less polar and less volatile than their non-esterified versions. A number of refining processes are now known in the art which aim specifically to remove organochlorine compounds which lead to the formation of chloropropanol fatty acid esters or to prevent their conversion by modifying process conditions.

In WO 2014/012548, a process is disclosed for lowering the amount of esters of 2- and 3-MCPD formed in refined triglyceride oil by blending with a base, heat treating while passing steam through the oil at reduced pressure and maintaining the degree of interesterification below 60%. This process benefits from a relatively mild heat treatment but involves the addition of free fatty acids (FFA) to the oil to suppress the degree of interesterification. However, the addition of FFA is thought to negatively impact the organoleptic properties of oil, as well as oil stability, and therefore additional process steps are likely to be required in order to remove FFA after it has been added.

In WO 201 1/005081 , a process is disclosed for removing unwanted propanol components, including free chloropropanols, chloropropanol fatty acid esters, free epoxypropanols, epoxypropanol fatty acid esters, and combinations thereof, from unused triglyceride oil. The process comprises contacting a contaminated oil with a silicate adsorbent selected from the group consisting of magnesium silicate, calcium silicate, aluminum silicate and combinations of these silicates. The oil to be treated is preferably a deodorized contaminated triglyceride oil.

In WO 2010/063450, a refining process is disclosed which involves degumming of crude oil with water, and without the addition of acids, at a temperature of less than 70 °C followed by wet bleaching and vacuum bleaching at a temperature in the range of 80 to 100 °C. It is reported that degumming and bleaching in this manner reduces 3-MCPD formation as a result of the overall refining process by removing both 3-MCPD and its precursors.

In WO 2012/107230, a process for the production of a refined oil having a reduced 3- MCPD ester and/or glycidyl ester content is disclosed, characterized in that it comprises subjecting an oil to the following steps, in order: (a) a bleaching step, (b) a deodorization step, (c) a final bleaching step, and (d) a final deodorization step, wherein final deodorization step (d) is carried out at a temperature of at least 40°C lower than deodorization step (b), preferably at a temperature below 190 °C.

In WO 2013/093093, a method of removing glycidyl esters from a vegetable oil is disclosed, which method comprises contacting the oil with at least 0.5 % by weight of the oil of an acid-activated bleaching earth and deodorising the oil at a temperature of less than 200°C for a time of at least 30 minutes. However, it is not clear whether such a deodorisation would be suitable for providing a commercially acceptable product in the case of oils having high levels of pigments and odiferous compounds.

In WO 2012/169718, a method is disclosed for reducing the concentration of 3- MCPD fatty acid esters to 0.3 ppm or less in refined edible oil by controlling chloride ions contained in the water source used for the refining process by means of an ion exchange resin.

In WO 2014/042937, a process is disclosed for removing monochloropropanediols and/or glycidol from glycerol which includes treatment with ion exchange resins, in particular strong base ion exchange resin in the hydroxyl form, to reduce the level of monochloropropanediol. Meanwhile, in JP 08-302382, a method is disclosed for deodorization and depigmentation of fish oil by contacting with a strongly basic anion-exchange resin under reduced pressure.

There remains a need for a process for preventing or reducing formation of chloropropanol fatty acid esters and/or glycidyl fatty acid esters in glyceride oil which may be capable of providing high value products whilst maximising energy savings for the overall refining process.

The present invention is based on the surprising discovery that specifically selected basic ionic liquids comprising a basic anion can be advantageously utilised for preventing or reducing formation of chloropropanol fatty acid esters and/or glycidyl fatty acid esters in glyceride oil, which treatment can be readily integrated into the overall refining process. In addition, treatment of glyceride oil with a basic ionic liquid has been found to at least partially remove pigments and odiferous compounds which are typically removed in a separate bleaching step and a high temperature (for example, 240 °C to 270 °C) deodorization step respectively during conventional refining processes. Treatment with a basic ionic liquid has also been found to at least partially degum glyceride oil.

Treatment of glyceride oil with basic ionic liquid means that it is possible to use lower temperatures and/or time periods for the deodorization step as part of the overall refining process and less extensive degumming and/or bleaching may be required, if at all. This has the advantage of reducing energy requirements and materials costs associated with the refining process.

Thus, in a first aspect, the present invention provides a process for refining glyceride oil comprising the steps of:

(i) contacting glyceride oil with a basic ionic liquid to form a treated glyceride oil; wherein the ionic liquid comprises a basic anion selected from hydroxide, alkoxide, alkylcarbonate, hydrogen carbonate, carbonate, serinate, prolinate, histidinate, threoninate, valinate, asparaginate, taurinate and lysinate; and a organic quaternary ammonium cation;

(ii) separating the treated glyceride oil from an ionic compound comprising the organic quaternary ammonium cation after contacting the glyceride oil with the basic ionic liquid; and

(iii) subjecting the treated glyceride oil after the separation step to at least one further refining step;

with the proviso that the glyceride oil does not comprise palm oil.

The term "glyceride oil" used herein refers to an oil or fat which comprises triglycerides as the major component thereof. For example, the triglyceride component may be at least 50 wt.% of the glyceride oil. The glyceride oil may also include mono- and/or di-glycerides. Preferably, the glyceride oil is at least partially obtained from a natural source (for example, a plant, animal or fish/crustacean source) and is also preferably edible. Glyceride oils include vegetable oils, marine oils and animal oils/fats which typically also include phospholipid components in their crude form.

Vegetable oils include all plant, nut and seed oils. Examples of suitable vegetable oils which may be of use in the present invention include: agai oil, almond oil, beech oil, cashew oil, coconut oil, colza oil, corn oil, cottonseed oil, grapefruit seed oil, grape seed oil, hazelnut oil, hemp oil, lemon oil, macadamia oil, mustard oil, olive oil, orange oil, peanut oil, pecan oil, pine nut oil, pistachio oil, poppyseed oil, rapeseed oil, rice bran oil, safflower oil, sesame oil, soybean oil, sunflower oil, walnut oil and wheat germ oil. Preferred, vegetable oils are those selected from coconut oil, corn oil, cottonseed oil, groundnut oil, olive oil, rapeseed oil, rice bran oil, safflower oil, soybean oil and sunflower oil.

Suitable marine oils include oils derived from the tissues of oily fish or crustaceans (e.g. krill). Examples of suitable animal oils/fats include pig fat (lard), duck fat, goose fat, tallow oil, and butter.

FFA which may be present in the glyceride oils include monounsaturated, polyunsaturated and saturated FFA. Examples of unsaturated FFA include: myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoelaidic acid, a-linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid and docosahexaenoic acid. Examples of saturated FFA include: caprylic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, heneicosylic acid, behenic acid, lignoceric acid and cerotic acid.

Preferably the glyceride oil used in the present invention is a vegetable oil. More preferably, the glyceride oil is a vegetable oil selected from coconut oil, corn oil, cottonseed oil, groundnut oil, olive oil, rapeseed oil, rice bran oil, safflower oil, soybean oil and sunflower oil.

The term "soybean oil" used herein includes oil extracted from the seeds of the soybean (Glycine max). The term "palm oil" used herein includes an oil at least partially derived from a tree of genus Elaeis, forming part of the Arecaceae genera, and including the species Elaeis guineensis (African oil palm) and Elaeis oleifera (American oil palm), or hybrids thereof. Reference to palm oil herein therefore also includes palm kernel oil as well as fractionated palm oil, for example palm oil stearin or palm oil olein fractions. The term "rapeseed oil" used herein is synonymous with canola oil and refers to the oil derived from a species of rape plant, for example rapeseed (Brassica napus L.) or field mustard/turnip rape (Brassica rapa subsp. oleifera, syn. B. campestris L).

The term "crude" used herein in reference to glyceride oil is intended to mean glyceride oil which has not undergone refining steps following oil extraction. For example, crude glyceride oil will not have undergone degumming, deacidification, winterisation, bleaching, depigmentation or deodorization. "Refined" used herein in reference to glyceride oil is intended to mean a glyceride oil which has undergone one or more refining steps, such as degumming, deacidification, winterisation, bleaching, depigmentation and/or deodorization.

"Chloropropanol" referred to herein corresponds to chloropropanols which may, for instance, derive from glycerol and which include monochloropropanol: 2-chloro-1 ,3- propanediol (2-MCPD) and 3-chloro-1 ,2-propanediol (3-MCPD), as well as dichloropropanol: 2,3-dichloropropan-1 -ol (2,3-DCP) and 1 ,3-dichloropropan-2-ol (1 ,3-DCP). Fatty acid esters of chloropropanols referred to herein correspond to the mono- or di-ester form of the chloropropanols formed from esterification with FFA.

Glycidol referred to herein corresponds to 2,3-epoxy-1 -propanol. Fatty acid esters of glycidol referred to herein correspond to the ester form of glycidol formed from esterification of glycidol with FFA.

The term "ionic liquid" as used herein refers to a liquid that is capable of being produced by melting a salt, and when so produced consists solely of ions. An ionic liquid may be formed from a homogeneous substance comprising one species of cation and one species of anion, or it can be composed of more than one species of cation and/or more than one species of anion. Thus, an ionic liquid may be composed of more than one species of cation and one species of anion. An ionic liquid may further be composed of one species of cation, and one or more species of anion. Still further, an ionic liquid may be composed of more than one species of cation and more than one species of anion.

The term "ionic liquid" includes compounds having both high melting points and compounds having low melting points, e.g. at or below room temperature. Thus, many ionic liquids have melting points below 200 °C, preferably below 150 °C, particularly below 100 °C, around room temperature (15 to 30 °C), or even below 0 °C. Ionic liquids having melting points below around 30 °C are commonly referred to as "room temperature ionic liquids". In room temperature ionic liquids, the structures of the cation and anion prevent the formation of an ordered crystalline structure and therefore the salt is liquid at room temperature.

The term "ionic liquid" as used herein also includes "non-classical" ionic liquids which exhibit ionic liquid properties but exist stably only in the presence of a solvent or on a support. For example, basic ionic liquids used in accordance with the present invention include quaternary ammonium hydroxide ionic liquids. These ionic liquids are typically considered to be "non-classical" ionic liquids because Hofmann elimination can make them unstable in neat form. Nevertheless, such ionic liquids are known to exist stably when immobilized on a support (see, for instance, Chem. Commun., 2004, 1096-1097) or in the presence of a solvent, for example an aqueous co-solvent. Basic ionic liquids used in accordance with the present invention also include quaternary ammonium bicarbonate ionic liquids. These ionic liquids are also typically considered to be "non-classical" ionic liquids because they may suffer from Hofmann elimination (although to far less extent than hydroxide based ionic liquids) as well as thermal decomposition of the bicarbonate anion to the carbonate form. Nevertheless, such ionic liquids are known to exist stably in the presence of a solvent, for example an aqueous solvent.

Thus, where a "non-classical" basic ionic liquid is used in accordance with the invention, a liquid may be used which includes the basic ionic liquid together with a solvent, such as an aqueous solvent. Additional co-solvents, such as an alcohol co- solvent, may also be present. Preferred embodiments, where the ionic liquids are used in combination with a solvent are discussed in more detail below. Ionic liquids are most widely known as solvents, because of their negligible vapour pressure, temperature stability, low flammability and recyclability, which also make them environmentally friendly. Due to the vast number of anion/cation combinations that are available it is possible to fine-tune the physical properties of the ionic liquid (e.g. melting point, density, viscosity, and miscibility with water or organic solvents) to suit the requirements of a particular application.

Ionic liquids have thus been exploited as solvents for various organic compound and polymer syntheses in the past due to their advantageous properties. There have been a number of reports which speculate upon the differing roles ionic liquids may play when used as solvents. S.-I. lshiguro et al., Pure Appl. Chem., Vol. 82, No.10, pp 1927 to 1941 , 2010, reports the crucial role that solute-solvent interaction, or solvation of solute ions or molecules, plays in reactions where ionic liquids can be considered to act as solvents. Particular emphasis is placed on the important role liquid structure of such solvents plays on reactions in solution, where solvent particles may be liberated upon reaction before being transferred and accommodated in the bulk liquid structure.

S.-I. lshiguro et al indicate that the liquid structure of ionic liquids is heterogeneous, unlike molecular solvents, which may bring about specific solvent properties, as well as specific solute reactivities in ionic liquids. However, they concede that the acid- base property of ionic liquids is, for instance, not satisfactorily established in terms of solution chemistry, particularly in comparison to normal molecular liquids. It is thus difficult to predict the role ionic liquids can serve in specific solution based reactions.

Where reference is made herein to an "ionic compound comprising the organic quaternary ammonium cation", it is intended to refer to an ionic compound which derives from the basic ionic liquid which is used for contacting the glyceride oil, at least by virtue of the organic quaternary ammonium cation. In some examples, the ionic compound comprising the organic quaternary ammonium cation may also comprise a chloride anion, as would be expected as a result of the basic ionic liquid undergoing anion exchange. In other examples, the glyceride oil contains FFA and the ionic compound comprising the organic quaternary ammonium cation also comprises an anion of a fatty acid. The ionic compound which is separated from the treated glyceride oil may also be an ionic liquid as defined herein, which is different to the basic ionic liquid which is used for contacting the glyceride oil initially. In further examples, the ionic compound comprising the organic quaternary ammonium cation comprises the same anion as the ionic liquid used for contacting the glyceride oil initially, in other words the ionic compound separated from the treated glyceride oil is the same as the ionic liquid used for contacting the glyceride oil initially.

The ionic liquids used in the process of the present invention are based on organic quaternary ammonium cations. "Organic quaternary ammonium cation" used herein is intended to refer to a positively charged ammonium cation wherein the nitrogen atom is bonded only to substituted or unsubstituted Ci to C12 hydrocarbyl groups. The term "hydrocarbyl group" refers to a univalent or multi-valent radical derived from a hydrocarbon and may include alkyl, cycloalkyi, alkenyl, alkynyl, or aryl groups.

Preferably, the organic quaternary ammonium cation of the basic ionic liquid is selected from:

[N(R^a)(R^b)(R^c)(R^d)]⁺, wherein: R^a, R^b, R^c and R^d are each independently selected from a Ci to Cs, straight chain or branched alkyl group or a C3 to C_& cycloalkyi group; or any two of R^a, R^b, R^c and R^d combine to form an alkylene chain -(CH₂)_q- wherein q is from 3 to 6; and wherein said alkyl or cycloalkyi groups may optionally be substituted by one to three groups selected from: Ci to C₄ alkoxy, C2 to Cs alkoxyalkoxy, C3 to C_& cycloalkyi, -OH, -SH, -C0₂(Ci to C₆)alkyl, and -OC(0)(Ci to C₆)alkyl, for example by one to three -OH groups.

More preferably, the organic quaternary ammonium cation of the basic ionic liquid is selected from:

[N(R^a)(R^b)(R^c)(R^d)]⁺, wherein: R^a, R^b, R^c and R^d are each independently selected from a Ci to Cs, straight chain or branched alkyl group; and wherein said alkyl group may optionally be substituted by one to three groups selected from: Ci to C₄ alkoxy, C₂ to C₈ alkoxyalkoxy, C₃ to C₆ cycloalkyl, -OH, -SH, -C0₂(Ci to C₆)alkyl, and -OC(0)(Ci to Ce)alkyl, for example by one to three -OH groups.

Even more preferably, the organic quaternary ammonium cation is selected from:

[N(R^a)(R^b)(R^c)(R^d)]⁺, wherein: R^a, R^b, R^c and R^d are each independently selected from a Ci to C₄, straight chain or branched alkyl group, including C-i, C₂ and C₄ alkyl, wherein at least one of R^a, R^b, R^c or R^d is substituted by a single -OH group. Most preferably, the organic quaternary ammonium cation is choline:

+

The basic ionic liquids used for the present invention incorporate basic anions selected from hydroxide, alkoxide, alkylcarbonate, hydrogen carbonate, carbonate, serinate, prolinate, histidinate, threoninate, valinate, asparaginate, taurinate and lysinate. These anions are not merely spectator anions selected by virtue of their ability to confer a certain melting point on the resulting ionic liquid. The basicity of the anions forming part of the ionic liquids used in conjunction with the present invention is believed to contribute to their ability to remove chloropropanol and glycidol, or their fatty acid esters, from glyceride oil. The term "basic" used herein refers to Bransted bases having the ability to react with (neutralise) acids to form salts. The pH range of bases is from above 7.0 to 14.0 when dissolved or suspended in water. In an embodiment of the present invention, the basic anion is selected from alkylcarbonate, hydrogen carbonate, carbonate, hydroxide and alkoxide; preferably hydrogen carbonate, alkylcarbonate and carbonate; and more preferably hydrogen carbonate.

Where the basic anion is selected from alkoxide or alkylcarbonate, the alkyl group may be linear or branched and may be substituted or unsubstituted. In one preferred embodiment, the alkyl group is unsubstituted. In another preferred embodiment, the alkyl group is unbranched. In a more preferred embodiment, the alkyl group is unsubstituted and unbranched.

The alkyl group may comprise from 1 to 10 carbon atoms, preferably from 1 to 8 carbon atoms and more preferably form 1 to 4 carbon atoms. The alkyl group may thus be selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl and/or decyl. It will be understood that branched alkyl groups such as iso-propyl, iso- butyl, sec-butyl and/or tert-butyl may also be used. Especially preferred are methyl, ethyl, propyl and butyl. In a further preferred embodiment, the alkyl group is selected from methyl and ethyl. In an embodiment of the present invention, the basic anion is selected from serinate, prolinate, histidinate, threoninate, valinate, asparaginate, taurinate and lysinate.

In a preferred embodiment of the present invention, the basic anion is selected from serinate, lysinate, prolinate, taurinate and threoninate, more preferably from lysinate, prolinate and serinate, most preferably the basic anion is lysinate.

It will be appreciated that in order for glyceride oil obtained directly from the process of the invention to be fit for consumption, the basic ionic liquid used for contacting the glyceride oil in step (i), as well as the ionic compound comprising the organic quaternary ammonium cation separated in step (ii), should have little or no toxicity and/or be readily and substantially separable from the treated oil. A basic ionic liquid comprising a choline cation is particularly suitable for use with the process of the present invention. Choline is a water soluble essential nutrient grouped with the B- complex vitamins which is a precursor to acetylcholine, involved in numerous physiological functions. Choline has particularly low toxicity and excellent biodegradability, making it a natural ingredient that is capable of forming an ionic liquid which is particularly useful in the process of the present invention. Thus, in particularly preferred embodiments of the present invention the basic ionic liquid is selected from choline bicarbonate:

or choline alkylcarbonate:

wherein the alkyl group is an alkyl group as described hereinbefore; or choline hydroxide:

Basic ionic liquids comprising a basic anion selected from serinate, prolinate, histidinate, threoninate, valinate, asparaginate, taurinate and lysinate are also particularly suitable in the process of the present invention due to the particularly low toxicity of these amino acid derivatives.

In the most preferred embodiments of the present invention, the basic ionic liquid is choline bicarbonate:

The basic ionic liquid used in contacting step (i), as well as the ionic compound comprising the organic quaternary ammonium cation separated in step (ii), preferably have low oil solubility and preferentially partition into a non-oil phase, such as an aqueous phase, facilitating their removal from the treated oil. More preferably, the basic ionic liquid is immiscible with the oil. By immiscible with the oil it is meant that the ionic liquid is soluble in the glyceride oil at a concentration of less than 50 ppm, preferably less than 30 ppm, more preferably less than 20 ppm, most preferably, less than 10 ppm, for example, less than 5 ppm. Thus, the solubility of the basic ionic liquid may be tailored so that the basic ionic liquid is immiscible with the oil.

Suitably, the contacting step (i) of the process of the present invention is carried out at a temperature of less than 80 °C, preferably from 25 to 65 °C, more preferably from 35 to 55 °C, for example, 40 °C. As will be appreciated, where the glyceride oil is semi-solid at room temperature, higher temperatures are preferable such that the glyceride oil is in a liquid form for contacting with the basic ionic liquid. Suitably, the contacting step (i) is carried out at a pressure of from 0.1 MPa absolute to 10 MPa absolute (1 bar absolute to 100 bar absolute).

In some embodiments, the contacting step may be carried out by contacting glyceride oil with the basic ionic liquid in a vessel wherein the resulting mixture is stirred using, for example, a mechanical stirrer, an ultrasonic stirrer, an electromagnetic stirrer or by bubbling an inert gas through the mixture.

Suitably, the basic ionic liquid and the glyceride oil may be contacted in a volume ratio of from greater than 1 :40 to 1 :300, and may be contacted in a mass ratio of from 1 :50, preferably from 1 : 100. The contacting step may last from 1 minute to 60 minutes, preferably 2 to 30 minutes, more preferably, 5 to 20 minutes and most preferably, 8 to 15 minutes. In the contacting step (i), the basic ionic liquid is contacted with the glyceride oil. The basic ionic liquid may added in neat form or as part of a liquid additionally comprising a solvent or mixture of solvents which is/are compatible with the basic ionic liquid and the glyceride oil. A solvent or mixture of solvents may be used to modify the viscosity of the basic ionic liquid as desired. Alternatively, use of a solvent may confer desirable properties on the liquid structure of the liquid based reaction that are particularly suitable for promoting the reaction of the basic ionic liquid. Suitable solvents for this purpose include polar solvents, such as water, or alcohol, for example methanol or ethanol.

In some embodiments, the glyceride oil is contacted with a liquid comprising the basic ionic liquid and a solvent, wherein the concentration of basic ionic liquid in the liquid is from 15 wt.% to 90 wt.%. In exemplary embodiments, the solvent is an aqueous solvent, such as deionised water.

In preferred embodiments, where the basic anion of the basic ionic liquid is selected from alkylcarbonate, hydrogen carbonate and carbonate, especially where the basic anion is hydrogen carbonate, the glyceride oil is contacted with a liquid comprising the basic ionic liquid and a solvent, such as an aqueous solvent, and the concentration of basic ionic liquid in the liquid is 50 wt.% to 90 wt.%, for example from 75 wt.% to 85 wt.%.

In preferred embodiments, where the basic anion of the basic ionic liquid is selected from hydroxide and alkoxide, especially where the basic anion is hydroxide, the glyceride oil is contacted with a liquid comprising the basic ionic liquid and a solvent, such as an aqueous solvent, wherein the concentration of basic ionic liquid in the liquid is 15 wt.% to 60 wt.%, preferably from 40 wt.% to 50 wt.%.

In the above embodiments where the basic ionic liquid is part of a mixture with a solvent, additional co-solvents may also be present. For instance, where an aqueous solvent is employed, alcohol co-solvent(s) may also be present, for example, at between 1 wt.% and 20 wt.% of the liquid comprising the basic ionic liquid and aqueous solvent. Separation of the ionic compound comprising the organic quaternary ammonium cation in step (ii) of the process, may be carried out by gravity separation (for example, in a settling unit), where the treated glyceride oil is generally the upper phase and the ionic compound comprising the organic quaternary ammonium cation together with any solvent are incorporated in the lower phase in the settling unit. Separation of the ionic compound comprising the organic quaternary ammonium cation may also be achieved using, for example, a decanter, a hydrocyclone, electrostatic coalesce, a centrifuge or a membrane filter press. Preferably, the phases are separated using a centrifuge. Contacting and separation steps may be repeated several times, for example 2 to 4 times.

Where the ionic compound comprising the organic quaternary ammonium cation separated in step (ii) is a solid which is precipitated after contacting step (i), for instance, following formation of a quaternary ammonium-FFA salt, the solid ionic compound may be separated from the oil by filtration. Alternatively, a polar solvent as described hereinbefore which is immiscible with the oil phase may be added to solubilise the solid salt, following which the salt-containing phase may be separated from the oil by the methods described above. Contacting and separation steps may also be carried out together in a counter- current reaction column. The glyceride oil (hereinafter "oil feed stream") is generally introduced at or near the bottom of the counter-current reaction column and the basic ionic liquid (hereinafter "ionic liquid feed stream") at or near the top of the counter- current reaction column. A treated oil phase (hereinafter "product oil stream") is withdrawn from the top of the column and a phase containing an ionic compound comprising the organic quaternary ammonium cation and solvent when present (hereinafter "secondary stream") from at or near the bottom thereof. Preferably, the counter-current reaction column has a sump region for collecting the secondary stream. Preferably, the oil feed stream is introduced to the counter-current reaction column immediately above the sump region. More than one counter-current reaction column may be employed, for example 2 to 6, preferably 2 to 3 columns arranged in series. Preferably, the counter-current reaction column is packed with a structured packing material, for example, glass Raschig rings, thereby increasing the flow path for the oil and basic ionic liquid through the column. Alternatively, the counter- current reaction column may contain a plurality of trays.

In particularly preferred embodiments, contacting and separating steps are carried out together in a centrifugal contact separator, for example, a centrifugal contact separator as described in US 4,959, 158, US 5,571 ,070, US 5,591 ,340, US 5,762,800, WO 99/12650, and WO 00/29120. Suitable centrifugal contact separators include those supplied by Costner Industries Nevada, Inc. Glyceride oil and the liquid comprising the ionic liquid may be introduced into an annular mixing zone of the centrifugal contact separator. Preferably, the glyceride oil and the basic ionic liquid are introduced as separate feed streams into the annular mixing zone. The glyceride oil and the basic ionic liquid are rapidly mixed in the annular mixing zone. The resulting mixture is then passed to a separation zone wherein a centrifugal force is applied to the mixture to produce a clean separation of an oil phase and a secondary phase.

Preferably, a plurality of centrifugal contact separators are used in series, preferably, 2 to 6, for example 2 to 3. Preferably, the oil feed stream is introduced into the first centrifugal contact separator in the series while the basic ionic liquid feed stream is introduced into the last centrifugal contact separator in the series such that oil of progressively decreasing content of, for instance, FFA or free chloride anions is passed from the first through to the last centrifugal contact separator in the series while a basic ionic liquid stream of progressively increasing content of, for instance, quaternary ammonium-FFA salt and/or quaternary ammonium chloride content is passed from the last through to the first centrifugal contact separator in the series. Thus, a phase containing an ionic compound comprising the organic quaternary ammonium cation is removed from the first centrifugal contact separator and the treated oil phase is removed from the last centrifugal contact separator in the series. If necessary, residual basic ionic liquid that is present in the treated glyceride may be recovered by passing the product oil stream through a silica column such that the residual ionic liquid is adsorbed onto the silica column. The adsorbed ionic liquid may then be washed off the silica column using a solvent for the ionic liquid and the ionic liquid may be recovered by driving off the solvent at reduced pressure. The treated glyceride oil may also be passed through a coalescer filter for coalescing fine droplets of non-oil phase liquid, for instance liquid comprising an ionic compound comprising the organic quaternary ammonium cation, so as to produce a continuous phase and facilitate phase separation. Preferably, where the basic ionic liquid used for contact step (i) is used in combination with a solvent, the coalescer filter is wetted with the same solvent to improve filtration.

In some embodiments, the basic ionic liquid may be provided on a support material. Suitable supports for use in the present invention may be selected from silica, alumina, alumina-silica, carbon, activated carbon or a zeolite. Preferably, the support is silica. The supported form may be provided for contact with the oil as a slurry comprising a suitable solvent, wherein the solvent is as described hereinbefore. Where supported basic ionic liquid is used, contacting and separation steps may also be carried out together by passing the oil through a column packed with the supported ionic liquid (i.e. a packed bed arrangement). In addition, or alternatively, a fixed-bed arrangement having a plurality of plates and/or trays may be used. Methods for supporting the ionic liquid on a support material are well known in the art, such as for example, in US 2002/0169071 , US 2002/0198100 and US 2008/0306319. Typically, the ionic liquid may be physisorbed or chemisorbed on the support material, and preferably physisorbed. In the processes of the present invention, the ionic liquid may be adsorbed onto the support in a basic ionic liquid:support mass ratio of from 10: 1 to 1 : 10, preferably in a basic ionic liquid:support mass ratio of from 1 :2 to 2: 1 .

It has been found that the basic ionic liquid used in accordance with the present invention is capable of preventing or reducing the formation of chloropropanol fatty acid esters and glycidyl fatty acid esters in glyceride oils as a result of subsequent refining steps. Several reaction mechanisms are believed to be possible as a result of contacting the oil with the basic ionic liquid, which are discussed in further detail below. Formation of chloropropanol fatty acid esters and glycidyl fatty acid esters has been found to depend predominantly on: (i) the mono- and di-glyceride content of the glyceride oil; (ii) the chloride content of the glyceride oil; (iii) the proton activity of the glyceride oil; and (iv) the extent of heat exposure during refining. Treatment of glyceride oil with the basic ionic liquid in accordance with the present invention has been found not to affect the mono- and di-glyceride content of the oil and thus it is believed that it is the chloride content and proton activity that are reduced, thereby leading to the prevention or reduction of chloropropanol fatty acid ester and glycidyl fatty acid ester formation during the refining process.

Without being bound by any particular theory, of the possible reactions or interactions of the basic ionic liquid in the oil, anion exchange with free chloride ions is considered to be a means by which the free chloride content of the oil may be reduced. Meanwhile, the basicity of the basic ionic liquid may also modify the proton activity of the oil such that glycidyl fatty acid ester formation is also reduced. For example, the ionic liquid used in accordance with the present invention has also been found to neutralise FFA present in the oil and form an ionic compound comprising the organic quaternary ammonium cation of the basic ionic liquid used in contact step (i) and the carboxylate anion of FFA. It is also possible that the product of the acid-base reaction between the basic ionic liquid and FFA in the oil may also complex chloride anions and/or chlorine-containing compounds and contribute to their removal from the oil upon separating the quaternary ammonium-FFA salt from the treated oil. Thus, in some embodiments, the ionic compound comprising the organic quaternary ammonium cation separated in step (ii) of the process may comprise a chloride anion. In embodiments where the glyceride oil which is contacted in step (i) comprises FFA, the ionic compound comprising the organic quaternary ammonium cation which is separated in step (ii) may comprise an anion of a fatty acid.

Preferably, the process of the invention is used to prevent or reduce the formation of chloropropanol fatty acid esters in glyceride oil. More preferably, the process of the invention is used to prevent or reduce the formation of monochloropropanol fatty acid esters in glyceride oil. Most preferably, the process of the invention is used to prevent or reduce the formation of 3-MCPD fatty acid ester in glyceride oil.

In accordance with the process of the present invention, at least one further refining step is conducted after treatment of the glyceride oil with the basic ionic liquid. The skilled person is aware of the different refining steps typically used in edible oil processing, including for example refining steps discussed in: "Practical Guide to Vegetable Oil Processing", 2008, Monoj K. Gupta, AOCS Press, as well as in the Edible Oil Processing section of the "AOCS Lipid Library" website (lipid!ibrar . aocs.org).

The at least one further refining step (iii) may, for instance, be selected from: degumming, bleaching, winterization, depigmentation and deodorisation. Since the heat exposure typically associated with the deodorisation step is known to be responsible for a large increase in the formation of chloropropanol fatty acid esters and glycidol fatty acid esters, the basic ionic liquid treatment preferably precedes deodorisation. Thus, in preferred embodiments, the at least one further refining step according to the process of the present invention comprises deodorisation. In some embodiments, the at least one further refining step (iii) comprises the steps of degumming, bleaching and deodorization. Alternatively, in other embodiments, the at least one further refining step (iii) comprises a deodorisation step and the process does not comprise a step of degumming and/or bleaching. Therefore, in exemplary embodiments, the at least one further refining step comprises the steps of degumming and deodorization, but no bleaching. In other exemplary embodiments, the at least one further refining step comprises the steps of bleaching and deodorization, but no degumming step.

An additional advantage of the treatment with basic ionic liquid in accordance with the present invention is that the basic ionic liquid has also been found to at least partially remove pigments and odiferous compounds which are typically removed in a high temperature (for example, 240 °C to 270 °C) deodorization step during conventional refining processes. Treatment of glyceride oil with the basic ionic liquid means that lower temperatures and/or time periods can be used for the deodorization step as part of the overall refining process. This has the advantage of reducing the energy requirements of the refining process.

Degumming typically involves contacting the oil with aqueous phosphoric acid and/or aqueous citric acid to remove both hydratable and non-hydratable phosphatides (NHP). Typically, citric acid or phosphoric acid is added as a 50 wt% aqueous solution. Suitably, the aqueous acid is used in an amount of about 0.02 % to about 0.20 % of acid by weight of oil, preferably 0.05 % to about 0.10 % of acid by weight of oil. Suitably, the degumming step is carried out at a temperature of from about 50 to 1 10 °C, preferably 80 °C to 100 °C, for example 90 °C. The degumming step may suitably last from 5 minutes to 60 minutes, preferably 15 to 45 minutes, more preferably, 20 to 40 minutes, for example 30 minutes. After settling of the mucilage following the acid treatment, the aqueous phase is separated before the degummed oil is typically dried. Drying of the degummed oil suitably takes place at a temperature of from 80 to 1 10 °C for a suitable time period, for example 20 to 40 min, at reduced pressure, for instance, at 2 to 3 kPa (20 to 30 mbar).

As the skilled person is aware, for glyceride oils with low phosphatide content (for example, less than 20 ppm by weight of phosphorus) a dry degumming process may be used in which the phosphoric acid or citric acid is added without significant dilution with water (for example, an 85 % acid solution). NHP are converted into phosphatidic acid and a calcium or magnesium bi-phosphate salt which can be removed from the oil in a subsequent bleaching step. For oils rich in phosphatides, particularly NHP, dry degumming is known to be less well suited since excessive amounts of bleaching earth are required.

Bleaching is incorporated into an edible oil refining process to reduce colour bodies, including chlorophyll, residual soap and gums, trace metals and oxidation products. Bleaching typically involves contacting the oil with an amount of bleaching clay or earth, for example from 0.5 to 5 wt.% clay based on the mass of the oil. Bleaching clays or earths are typically composed of one or more of three types of clay minerals: calcium montmorillonite, attapulgite, and sepiolite. Any suitable bleaching clay or earth may be used in accordance with the present invention, including neutral and acid activated clays (e.g. bentonite). The oil is suitably contacted with bleaching clay for 15 to 45 minutes, preferably 20 to 40 minutes before the earth is separated, typically be filtratio. The oil is typically contacted with bleaching clay or earth at a temperature of from 80 °C to 125 ° C, preferably at a temperature of from 90 ° C to 1 10 ° C. Following an initial period of contact ("wet bleaching") conducted under atmospheric pressure, a second stage of the bleaching process is conducted under reduced pressure ("dry bleaching"), for example at 2 to 3 kPa (20 to 30 mbar).

Conventional glyceride oil refining processes typically include a FFA neutralisation step with a strong base, for example sodium hydroxide or potassium hydroxide (corresponding to a so called "chemical refining" process). Alternatively, deacidification can be achieved by adjusting the deodorisation parameters accordingly to ensure that volatile FFA is removed in that step (a so called "physical refining" process). A disadvantage of a FFA neutralisation step ("chemical refining") is that it is accompanied by unwanted saponification, lowering triglyeride content, whilst soap formation can lead to substantial neutral oil losses as a result of emulsification. The basic ionic liquid treatment forming part of the refining process of the present invention is effective at neutralising FFA in the oil and may entirely replace a conventional neutralisation step used in a chemical refining process. Advantageously, treatment with the basic ionic liquid has the benefit that it does not lead to saponification of neutral oil. Thus, in preferred embodiments of the present invention, the refining process does not include a neutralisation step with an inorganic base (e.g. sodium hydroxide).

FFA present in the oil may be neutralised upon contact with the basic ionic liquid to form a quaternary ammonium-FFA salt. In preferred embodiments, the amount of basic ionic liquid employed in the contacting step is at least stoichiometric with the molar amount of FFA contained in the oil. For example, the molar ratio of the basic ionic liquid to FFA in the oil may be from 1 : 1 to 10 : 1 , or from 1.5 : 1 to 5 : 1 . The content of FFA in the glyceride oil may be determined prior to treatment with basic ionic liquid using common titration techniques, of which the person of skill in the art is aware. For instance, titration with sodium hydroxide using phenolphthalein indicator may be used to determine the FFA content of glyceride oil. In preferred embodiments, the organic quaternary ammonium cation is selected to provide low melting fatty acid salts with linear C12 to C18 FFAs. Particularly preferred organic quaternary ammonium cations form salts with such FFAs having melting points of less than 100 °C. Such salts may be conveniently separated during separation step (ii) by liquid-liquid separation techniques discussed herein.

As the skilled person is aware, deodorization corresponds to a stripping process in which an amount of stripping agent is passed through an oil in a distillation apparatus, typically by means of direct injection, at reduced pressure for a period of time so as to vaporize and extract volatile components, such as FFA, aldehydes, ketones, alcohols, hydrocarbons, tocopherols, sterols, and phytosterols. The stripping agent is preferably steam, although other agents such as nitrogen may be used. The amount of stripping agent suitably used is from about 0.5 % to about 5 % by weight of oil.

The temperature range of deodorization for the refining process according to the present invention is suitably from 160 °C to 270 °C. Where reference is made herein to the temperature of the deodorization step, this refers to the temperature the oil is heated to before being exposed to the stripping agent. The pressure range of deodorization is suitably from 0.1 to 0.4 kPa (1 to 4 mbar), preferably 0.2-0.3 kPa (2 to 3 mbar). Suitable time periods for deodorization are typically from 30 to 180 minutes, for example 60 to 120 minutes, or 60 to 90 minutes.

The skilled person is able to determine a suitable length of deodorization by analysing the appearance and composition of the glyceride oil. For instance, determining the p-anisidine value (AnV) of the oil. The p-anisidine value of an oil is a measure of its oxidative state and, more specifically, provides information regarding the level of secondary oxidation products contained in an oil, although primarily aldehydes such as 2-alkenals and 2,4-dienals. The p-anisidine value (AnV) therefore also gives an indication of the level of oxidation products which are intended to be removed by means of the deodorization step. For instance, satisfactory deodorization may be achieved where, for example, the AnV is less than 10, preferably less than 5, as determined by AOCS Official Method Cd 18-90. In addition or alternatively, the amount of aldehyde and ketone components of the oil can be determined, which are typically associated with a crude oil's odour, to determine whether sufficient deodorization has taken place. Typical volatile odiferous aldehyde and ketone components of crude or rancid palm oil include: acetaldehyde, benzaldehyde, n-propanal, n-butanal, n-pentanal, n-hexanal, n-octanal, n-nananal, 2- butenal, 3-methylbutanal, 2-methylbutanal, 2-pentenal, 2-hexenal, 2E,4E-decadienal, 2E,4Z-decadienal, 2-butanone, 2-pentanone, 4-methyl-2-pentanone, 2-heptanone, 2- nonanone. Preferably, each of these components is individually present in a deodorized oil in an amount less than 3 mg/kg of oil, more preferably less than 1 mg/kg of oil, most preferably less than 0.5 mg/kg of oil.

The amount of aldehydes and ketones may be readily determined by chromatographic methods, for instance GC-TOFMS or GCxGC-TOFMS. Alternatively, derivatization of aldehydes and ketones may be used to improve chromatographic analysis. For example, it is known that aldehydes and ketones may be derivatized with 2,4-dinitrophenylhydrazine (DNPH) under acidic conditions. This reagent does not react with carboxylic acids or esters and therefore the analysis is not affected by the presence of such components in a glyceride oil sample. Following derivatization, HPLC-UV analysis can quantify the total amount of aldehydes and ketones which are present in a sample.

Conventional deodorisation temperatures are typically in excess of 220 °C, for example 240 °C to 270 °C, and typically operated for 60 to 90 minutes. Where lower than conventional temperatures are used for deodorisation as allowed by the process of the present invention, for example 160 °C to 200 °C, the time periods for deodorization may be lengthened to ensure sufficient deodorization, yet still involve less energy consumption than a conventional deodorization operated at higher temperature, for example 240 °C to 270 °C, for a shorter period. In preferred embodiments, the same or lower than conventional deodorization time periods are used in combination with the lower than conventional deodorization temperature, yet achieve the same extent of deodorization as a result of the preceding basic ionic liquid treatment. In other preferred embodiments, where conventional temperatures are used for the deodorization step included in the refining process of the invention, for example 240 °C to 270 °C, the time period for the deodorization may be reduced compared to that which is conventionally used and still achieve a comparable level of deodorization as a result of the preceding the basic ionic liquid treatment.

The basic ionic liquid treatment therefore also has the advantage that it may reduce energy consumption during a subsequent deodorization step. In addition, by reducing either the temperature or time period of exposure to heat during the deodorization step then side reactions that can lead to undesirable organoleptic properties of the oil, or formation of unwanted, potentially harmful by-products, may also advantageously be reduced.

In particularly preferred embodiments, where the at least one further refining step according to the process of the present invention comprises deodorisation, the temperature of the deodorization is from 160 °C to 200 °C, more preferably 170 °C to 190 °C. Preferably, the time periods over which deodorization is conducted at these temperatures is from 30 to 150 minutes, more preferably 45 to 120 minutes, most preferably 60 to 90 minutes. The basic ionic liquid treatment according to the process of the present invention may suitably be applied to crude glyceride oil which has not undergone any previous refining steps following oil extraction. Alternatively, the process of the present invention may be applied to glyceride oil which has undergone at least one additional refining step prior to treatment with basic ionic liquid. Preferably, the at least one additional refining step is selected from bleaching and/or degumming.

As discussed above, degumming typically involves the addition of citric acid and/or phosphoric acid to remove phospholipids in the oil. It is possible that this step can negatively impact on the proton activity of the oil so as to increase the formation of glycidyl fatty acid esters on exposure to heat. It is also known that bleaching clay or earth which has been acid activated can be a source of contaminants such as chloride anions, for instance where hydrochloric acid has been used for acid activation. Such acid activated bleaching earth or clay can also modify the proton activity and potentially increase formation of glycidyl fatty acid ester formation on subsequent exposure to heat.

As such, in some embodiments, it is preferred that degumming precedes the basic ionic liquid treatment since this provides for the proton activity of the oil to be modified by the basic ionic liquid after exposure of the glyceride oil to acid. In some embodiments, it is preferred that bleaching, particularly where a material comprising a source of chloride anions is used, precedes the basic ionic liquid treatment since this provides the opportunity for such contaminants to be removed by the basic ionic liquid treatment.

Advantageously, it has been found that the basic ionic liquid treatment forming part of the process of the present invention is also capable of at least partially degumming the oil and removing pigments which means that the extent of degumming and bleaching steps can be scaled back, for example, in terms of treatment time or materials. As mentioned above, the basic ionic liquid treatment forming part of the process of the present invention obviates a separate FFA neutralisation step used in a chemical refining process. Meanwhile, the basic ionic liquid treatment forming part of the process of the present invention may also be capable of reducing energy consumption in a deodorization step.

The basic ionic liquid treatment used in accordance with the present invention is intended to obviate the use of ion exchange resins and ultrafiltration membranes and the like for removing contaminants which can contribute significantly to the materials costs associated with glyceride oil refining. Thus, in preferred embodiments, the refining processes described herein do not comprise treatment of the glyceride oil with ion exchange resins or ultrafiltration membranes.

In some embodiments, the basic ionic liquid used in contact step (i) may be regenerated from the ionic compound comprising the organic quaternary ammonium cation separated in step (ii) (where these salts are different) by means of a regeneration process in order to recycle the basic ionic liquid to the refining process of the invention, if desired. For instance, a regeneration process may comprise anion or cation exchange steps to obtain a basic ionic liquid comprising the desired basic anion as described hereinbefore.

In an embodiment, the regeneration process comprises forming a basic ionic liquid which is choline bicarbonate from a choline-FFA salt; comprising the steps of:

(a) contacting the choline-FFA salt with carbonic acid; and

(b) obtaining choline bicarbonate from the reaction mixture. Preferably, step (a) is performed by contacting an aqueous solution comprising the choline-FFA salt with C0₂ (e.g. by bubbling C0₂ through the aqueous solution).

Preferably, step (b) is performed by contacting the mixture of step (a) with a solvent which is miscible with choline bicarbonate and separating the solvent from choline bicarbonate.

The present invention also provides a use of a basic ionic liquid as described hereinbefore for preventing or reducing formation of fatty acid esters of chloropropanol and/or glycidol in glyceride oil during a heating step by contacting the oil with the basic ionic liquid prior to the heating step. The heating step may, for instance, correspond to heating the oil to temperatures in excess of, for example, 150 °C, 200 °C or even 250 °C, where substantial formation of fatty acid esters of chloropropanol and/or glycidol in glyceride oil would normally be expected. The heating step may therefore form part of a deodorization step.

Preferably, the basic ionic liquid is used to prevent or reduce the formation of chloropropanol fatty acid esters in the glyceride oil. More preferably, the basic ionic liquid is used to prevent or reduce formation of monochloropropanol fatty acid esters. Most preferably, the ionic liquid is used to prevent or reduce the formation of 3- MCPD fatty acid ester in the glyceride oil. Preferred embodiments of other aspects of the invention relating to the nature of the anion and cation of the basic ionic liquid, as well as the nature of the glyceride oil, equally apply to this aspect of the invention. For instance, it is most preferred that the ionic liquid is choline bicarbonate. An analytical method for determining the concentration of MCPD in glyceride oil is described in R.Weiphaar, "Determination of total 3-chloropropane-1 ,2-diol (3-MCPD) in edible oils by cleavage of MCPD esters with sodium methoxide", Eur. J. Lipid Sci. Technol. (2008) 1 10, 183-186. The amended German Society for Fat Science (DGF) Standard Method C-lll 18(10) (German Standard Methods 2010) also provides a suitable procedure for determining the level of MCPD, or fatty acid esters thereof, as well as an indirect method for determining the presence of glycidol, or fatty acid esters thereof. Direct procedures for determining the content of chloropropanol and glycidol and their fatty acid esters involves use of Liquid Chromatography - Time of Flight Mass Spectrometry (LC-TOFMS), as reported in J Am Oil Chem Soc. Jan 201 1 ; 88(1 ): 1 -14.

Embodiments of the invention described hereinbefore may be combined with any other compatible embodiments to form further embodiments of the invention. As will be appreciated by the skilled person, all aspects of the present invention may be applied to the treatment and refining of palm oil or glyceride oil mixtures comprising palm oil. In a specific example, the present invention also covers processes described herein wherein the glyceride oil comprises or consists of palm oil where the process further comprises a regeneration step as described hereinbefore.

The present invention will now be illustrated by way of the following examples.

EXAMPLES General method for determination of Acid Value (mg KOH/g of oil) and FFA (wt.%) content of glyceride oil

To a beaker containing 60ml of isopropyl alcohol was added 0.5mL of phenolphthalein. This mixture was heated until boiling and 0.02M potassium hydroxide in isopropyl alcohol was added until a faint pink colour persisted for approximately 10 s.

To a glass vial was added 0.200g of the glyceride oil sample which was subsequently dissolved in 50 ml of the above hot isopropyl alcohol solution. The resulting solution was titrated whilst stirring with 0.02M potassium hydroxide solution using a 25 ml burette graduated in 0.1 ml to the end point of the phenolphthalein indicator i.e until the pink colour persisted for at least 30 s. The Acid Value (mg KOH/g of oil) was subsequently calculated using the formula:

56.1 x N x V / m where:

56.1 is the Mr of potassium hydroxide;

V is the volume (ml) of potassium hydroxide solution used;

N is the normality of the potassium hydroxide solution; and

m is the mass (g) of the glyceride oil sample. Once the Acid Value has been determined, the FFA content may be derived. The FFA content for the purposes of the present disclosure is defined as a mass percentage while assuming the FFA to be an equal mixture of palmitic acid (Mr = 256 g/mol) and oleic acid (Mr = 282 g/mol), giving an average molecular weight of 269 g/mol. Oil with an FFA of 1 wt.% contains 0.01 g of oleic/palmitic acid per 1 g of oil, which amount of oleic/palmitic acid corresponds to 3.171 x 10^"5 mol (0.01/269). The amount of KOH required to neutralise this amount of oleic/palmitic acid (i.e. the Acid Value - AV) is calculated to be 2.086 mg of KOH/g of oil (3.171 x 10^"5 x 56.1 ). Calculation of FFA content (wt.%) therefore has the following formula: Wt.% FFA = Acid Value x 0.479

Example 1 : Ionic liquid treatment of corn oil

Corn oil (10 g) was analysed for its FFA content and doped with stearic acid to give an FFA content of 5 wt.%. The doped oil was sample was heated to 60 °C before 0.363g of a choline bicarbonate solution (80 w/w% in H₂O supplied by Sigma-Aldrich UK) was added. The mixture was rapidly stirred for 30 minutes before being centrifuged at 4400 rpm for 2 minutes. The upper oil phase was removed and analysed for FFA content. Results are provided in Table 1 below.

Example 2: Ionic liquid treatment of olive oil

The method of Example 1 was repeated except that an olive oil sample was used in place of corn oil. Results are provided in Table 1 below.

Example 3: Ionic liquid treatment of castor oil

The method of Example 1 was repeated except that a castor oil sample was used in place of corn oil. Results are provided in Table 1 below.

Example 4: Ionic liquid treatment of rapeseed (canola) oil

The method of Example 1 was repeated except that a rapeseed oil sample was used in place of corn oil. Results are provided in Table 1 below.

Example 5: Ionic liquid treatment of cow's milk butter

The method of Example 1 was repeated except that a butter sample was used in place of corn oil. Results are provided in Table 1 below.

Table 1

The results of Table 1 demonstrate that the basic ionic liquid treatment is capable of removing FFA from a variety of different oils. Furthermore, the results demonstrate that the basic ionic liquid treatment is capable of lowering the proton activity of the oil. This property has been found to be a significant promotor of chloropropanol fatty acid ester and glycidyl fatty acid ester formation in a subsequent deodorization step.

When each of the above treated oils is subsequently exposed to heating in a flask (with heating mantle) at 260 °C for 90 minutes under a flow of steam (1 % by mass / h of water) at reduced pressure (0.1 kPa), the levels of MCPD fatty acid esters and glycidyl fatty acid esters (determined using standard method DGF-C-VI 18, Part A, and DGF standard method C-VI 17 (10)) is found to be significantly reduced in comparison to the levels observed in samples of the oils doped with stearic acid not having undergone the ionic liquid treatment.

Example 6: ionic liquid treatment of cow's milk butter

1 .5 g of butter was placed in a sample vial before being doped with unbound 3- MCPD (supplied by Sigma-Aldrich UK). The resulting mixture was stirred for 3 h at 40 °C to ensure thorough mixing of the oil and dopant before the concentration of dopant in the oil was determined. Choline bicarbonate (100mg, 80 w/w% in H₂0 supplied by Sigma-Aldrich UK) was subsequently added to the oil/dopant mixture and the resulting mixture stirred for approximately 12 h at 40 °C. The mixture was then centrifuged at 2500 rpm for 10 minutes. The upper oil phase was then removed and a small sample of the oil phase taken for analysis. Results are provided in Table 2 below.

Example 7: ionic liquid treatment of corn oil

The method of Example 6 was repeated except that corn oil was used in place of butter and the mixing and contacting with choline bicarbonate was conducted at room temperature. Results are provided in Table 2 below. Example 8: ionic liquid treatment of olive oil

The method of Example 6 was repeated except that corn oil was used in place of butter and the mixing and contacting with choline bicarbonate was conducted at room temperature. Results are provided in Table 2 below. Table 2

The methodology used for analysis of the oils is that proposed by R.Weiphaar, "Determination of total 3-chloropropane-1 ,2-diol (3-MCPD) in edible oils by cleavage of MCPD esters with sodium methoxide", Eur. J. Lipid Sci. Technol. (2008) 1 10, 183- 186. This method involves extraction of 3-MCPD, derivatisation with phenylboronic acid and subsequent analysis using GC-MS (a deuterium-labelled internal standard (3-MCPD-d₅) is also added to each sample).

Quantitative analysis was carried out using a calibration curve with increasing standard solutions spiked with deuterium-labelled 3-MCPD. The ions m/z 147 (3- MCPD) and m/z 150 (3-MCPD-d₅) were the target ions. Ions at m/z 196 (3-MCPD) and m/z 201 (3-MCPD-d₅) were the qualifiers. The detection limit of this methodology is 0.15 mg/kg.

The results in Table 2 demonstrate that the basic ionic liquid treatment is capable of removing a substantial amount of organochlorine compounds, such as 3-MCPD itself, from the oil. The ionic liquid treatment is therefore capable of removing chloride sources from the oil which are implicated in the formation of chloropropanol fatty acid esters as discussed hereinbefore in a subsequent deodorization step.

Claims

1 . A process for refining glyceride oil comprising the steps of:

(i) contacting glyceride oil with a basic ionic liquid to form a treated glyceride oil; wherein the basic ionic liquid comprises a basic anion selected from hydroxide, alkoxide, alkylcarbonate, hydrogen carbonate, carbonate, serinate, prolinate, histidinate, threoninate, valinate, asparaginate, taurinate and lysinate; and a organic quaternary ammonium cation;

with the proviso that the glyceride oil does not comprise palm oil.

2. A process according to Claim 1 , wherein the at least one further refining step is selected from: degumming, bleaching, winterization, depigmentation and deodorisation, preferably wherein the at least one further refining step comprises deodorisation.

3. A process according to Claim 2, wherein the at least one further refining step comprises a deodorisation step, preferably involving steam stripping, conducted at a temperature of from 160 to 270 °C, preferably at a temperature of from 160 °C to 240 °C, more preferably at a temperature of from 170 °C to 190 °C.

4. A process according to any of the preceding claims, wherein the process further comprises at least one additional refining step of the glyceride oil which is conducted prior to the treatment with the basic ionic liquid in step (i), preferably wherein the at least one additional refining step is selected from bleaching and/or degumming.

5. A process according to Claim 4, wherein the at least one additional refining step is a bleaching step with bleaching earth comprising a source of chloride anions, such as hydrochloric acid activated bleaching earth.

6. A process according to any of Claims 1 to 3, wherein the at least one further refining step (iii) comprises a deodorisation step and the process does not comprise a step of degumming and/or bleaching.

7. A process according to any of the preceding claims, wherein the ionic compound separated in step (ii) comprises one or more chloride anions.

8. A process according to any of Claims 1 to 6, wherein the ionic compound separated in step (ii) comprises an anion of a free fatty acid.

9. A process according to any of the preceding claims, wherein the contacting step is conducted at a temperature of less than 80 °C, preferably from 25 to 65 °C, more preferably from 35 to 55 °C.

10. A process according any of the preceding claims, wherein the organic quaternary ammonium cation of the basic ionic liquid is selected from:

[N(R^a)(R^b)(R^c)(R^d)]⁺, wherein: R^a, R^b, R^c and R^d are each independently selected from a Ci to Cs, straight chain or branched alkyl group or a C3 to C6 cycloalkyl group; or any two of R^a, R^b, R^c and R^d combine to form an alkylene chain -(CH₂)_q- wherein q is from 3 to 6; and wherein said alkyl or cycloalkyl groups may optionally be substituted by one to three groups selected from: Ci to C₄ alkoxy, C2 to Cs alkoxyalkoxy, C₃ to C₆ cycloalkyl, -OH, -SH, - C0₂(Ci to C₆)alkyl and -OC(0)(Ci to C₆)alkyl, for example one to three -OH groups.

1 1 . A process according to Claim 10, wherein the organic quaternary ammonium cation of the basic ionic liquid is selected from:

[N(R^a)(R^b)(R^c)(R^d)]⁺, wherein: R^a, R^b, R^c and R^d are each independently selected from a Ci to Cs, straight chain or branched alkyl group; and wherein said alkyl group may optionally be substituted by one to three groups selected from: Ci to C₄ alkoxy, C2 to Cs alkoxyalkoxy, C3 to C₆ cycloalkyl, -OH, -SH, -C0₂(Ci to C₆)alkyl and - OC(O)(Ci to C₆)alkyl, for example one to three - OH groups.

12. A process according to Claim 1 1 , wherein the organic quaternary ammonium cation of the basic ionic liquid is selected from:

[N(R^a)(R^b)(R^c)(R^d)]⁺, wherein: R^a, R^b, R^c and R^d are each independently selected from a Ci to C₄, straight chain or branched alkyl group, including C-i , C2 and C₄ alkyl, wherein at least one of R^a, R^b, R^c or R^d is substituted by a single -OH group.

13. A process according to Claim 12, wherein the organic quaternary ammonium cation is choline: / OH

14. A process according to any of the preceding claims, wherein the basic anion is selected from alkylcarbonate, hydrogen carbonate and carbonate, preferably wherein the basic anion is hydrogen carbonate.

15. A process according to Claim 14, wherein the ionic liquid used for contacting the glyceride oil in step (i) is choline bicarbonate:

16. A process according to any of Claims 1 to 13, wherein the basic anion is selected from hydroxide and alkoxide, preferably wherein the basic anion is hydroxide.

17. A process according to Claim 16, wherein the basic ionic liquid used for contacting the glyceride oil in step (i) is choline hydroxide:

18. A process according to any of the preceding claims, wherein the glyceride oil is contacted with a liquid comprising the basic ionic liquid and a solvent, such as an aqueous solvent, and the concentration of ionic liquid in the liquid is 15 wt.% to 90 wt.%.

19. A process according to Claim 14 or Claim 15, wherein the glyceride oil is contacted with a liquid comprising the basic ionic liquid and a solvent, such as an aqueous solvent, and wherein the concentration of ionic liquid in the liquid is 50 wt.% to 90 wt.%, preferably from 75 wt.% to 85 wt.%.

20. A process according to Claim 16 or Claim 17, wherein the glyceride oil is contacted with a liquid comprising the basic ionic liquid and a solvent, such as an aqueous solvent, and wherein the concentration of ionic liquid in the liquid is 15 wt.% to 60 wt.%, preferably from 40 wt.% to 50 wt.%.

21 . A process according to Claim 15, wherein the glyceride oil which is contacted comprises FFA and the ionic compound separated from the glyceride oil is a choline-FFA salt, and wherein the process further comprises a step of regenerating the choline bicarbonate basic ionic liquid from the ionic compound which is a separated from the treated oil; said regeneration comprising the steps of:

(a) contacting the choline-FFA salt with carbonic acid; and (b) obtaining choline bicarbonate from the reaction mixture.

22. A process according to Claim 21 , wherein step (a) of the regeneration is performed by contacting an aqueous solution comprising the choline-FFA salt with C0₂.

23. A process according to any of the preceding claims, wherein the glyceride oil is a vegetable oil, preferably wherein the vegetable oil is selected from coconut oil, corn oil, cottonseed oil, groundnut oil, olive oil, rapeseed oil, rice bran oil, safflower oil, soybean oil and sunflower oil, or mixtures thereof.

24. Use of a basic ionic liquid for preventing or reducing the formation of chloropropanol fatty acid esters and/or glycidyl fatty acid esters in glyceride oil during a heating step by contacting the oil with a the basic ionic liquid prior to the heating step; with the proviso that the glyceride oil does not comprise palm oil; wherein the basic ionic liquid comprises a basic anion selected from hydroxide, alkoxide, alkylcarbonate, hydrogen carbonate, carbonate, serinate, prolinate, histidinate, threoninate, valinate, asparaginate, taurinate and lysinate; and a organic quaternary ammonium cation.

25. A use according to Claim 24, wherein the glyceride oil is as defined in Claim 23 and/or wherein the basic ionic liquid is as defined in any of Claims 10 to 17.

26. Use according to Claim 24 or Claim 25, where the basic ionic liquid is used to prevent or reduce the formation of monochloropropanol fatty acid esters and/or glycidyl fatty acid esters in the glyceride oil; more preferably wherein the basic ionic liquid is used to prevent or reduce the formation of monochloropropanol fatty acid esters in glyceride oil; and most preferably wherein the basic ionic liquid is used to prevent or reduce the formation of 3- MCPD fatty acid esters in glyceride oil.