Process for removing chloropropanols and/or glycidol, or their fatty acid esters, from glyceride oil, and an improved glyceride oil refining process comprising the same

Abstract

The present invention is directed to a basic ionic liquid treatment for removing chloropropanol and/or glycidol, or their fatty acid esters, from glyceride oil, as well as a process for refining glyceride oil which includes the basic ionic liquid treatment. The present invention also relates to uses of the basic ionic liquid and glyceride oil compositions obtained from the ionic liquid treatment.

Claims

1. A process for removing chloropropanol and/or glycidol, or their fatty acid esters, from glyceride oil comprising the steps of: (i) contacting glyceride oil comprising chloropropanol and/or glycidol, or their fatty acid esters, 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 an organic quaternary ammonium cation; and (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; wherein the treated glyceride oil has a reduced concentration of chloropropanol and/or glycidol, or their fatty acid esters, compared to the glyceride oil contacted in step (i).

2. A process according to claim 1, wherein the process further comprises subjecting the glyceride oil to at least one refining step before and/or after contacting the glyceride oil with the basic ionic liquid.

3. A process according to claim 2, wherein the at least one refining step is selected from: degumming, bleaching, winterization, depigmentation and deodorization.

4. A process according to claim 3, wherein the at least one refining step comprises deodorization.

5. A process according to claim 4, wherein the deodorisation includes steam stripping and is conducted at a temperature of from 160 to 270 C., or at a temperature of from 160 C. to 200 C., or at a temperature of from 170 C. to 190 C.

6. A process according to claim 1, wherein the total concentration of monochloropropanol and fatty acid esters thereof, in the glyceride oil which is contacted with the basic ionic liquid is from 0.01 ppm to 30 ppm.

7. A process according to claim 1, wherein the treated glyceride oil which is separated has a total concentration of monochloropropanol and fatty acid esters thereof which is at least 50 wt. %, or at least 75 wt. %, lower than that of the glyceride oil which is contacted with the basic ionic liquid; or wherein the treated glyceride oil which is separated has a total concentration of glycidyl fatty acid esters which is at least 50 wt. %, or at least 75 wt. %, lower than that of the glyceride oil contacted with the basic ionic liquid.

8. A process according to claim 1, wherein the step of contacting the glyceride oil with the basic ionic liquid is conducted at a temperature of less than 80 C., or from 25 to 65 C., or from 35 to 55 C.

9. A process according to claim 1, wherein the organic quaternary ammonium cation of the basic ionic liquid is selected from:
[N(R.sup.a)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+, wherein: R.sup.a, R.sup.b, R.sup.c and R.sup.d are each independently selected from a C.sub.1 to C.sub.8, straight chain or branched alkyl group or a C.sub.3 to C.sub.6 cycloalkyl group; or any two of R.sup.a, R.sup.b, R.sup.c and R.sup.d combine to form an alkylene chain (CH.sub.2).sub.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: C.sub.1 to C.sub.4 alkoxy, C.sub.2 to C.sub.8 alkoxyalkoxy, C.sub.3 to C.sub.6 cycloalkyl, OH, SH, CO.sub.2(C.sub.1 to C.sub.6)alkyl and OC(O)(C.sub.1 to C.sub.6)alkyl, for example one to three OH groups; or wherein the organic quaternary ammonium cation of the basic ionic liquid is selected from:
[N(R.sup.a)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+, wherein: R.sup.a, R.sup.b, R.sup.c and R.sup.d are each independently selected from a C.sub.1 to C.sub.4, straight chain or branched alkyl group, including C.sub.1, C.sub.2 and C.sub.4 alkyl, wherein at least one of R.sup.a, R.sup.b, R.sup.c or R.sup.d is substituted by a single OH group.

10. A process according to claim 9, wherein the organic quaternary ammonium cation of the basic ionic liquid is choline: ##STR00009##

11. A process according to claim 1, wherein the basic anion is selected from alkylcarbonate, hydrogen carbonate and carbonate.

12. A process according to claim 1, wherein the basic anion is selected from hydroxide and alkoxide.

13. A process according to claim 1, wherein 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 15 wt. % to 90 wt. %.

14. A process according to claim 13, wherein the glyceride oil is contacted with a liquid comprising the basic ionic liquid and a solvent, wherein i) the concentration of basic ionic liquid in the liquid is 50 wt. % to 90 wt. %, or from 75 wt. % to 85 wt, and the basic ionic liquid is as defined in claim 11; or ii) the concentration of basic ionic liquid in the liquid is 15 wt. % to 60 wt. %, or from 40 wt. % to 50 wt, and the basic ionic liquid is as defined in claim 12.

15. A process according to claim 11, wherein the basic ionic liquid is choline bicarbonate and 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.

16. A process according to claim 1, wherein the glyceride oil is a vegetable oil selected from coconut oil, corn oil, cottonseed oil, groundnut oil, olive oil, palm oil, rapeseed oil, rice bran oil, safflower oil, soybean oil and sunflower oil, or mixtures thereof.

17. A composition comprising a glyceride oil and a basic ionic liquid; 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; and wherein the glyceride oil of the composition has a total aldehyde and ketone content of less than 20 mg/kg; and/or wherein the p-anisidine value of the oil is less than 10.

18. A composition according to claim 17, wherein the total concentration of monochloropropanol and fatty acid esters thereof in the glyceride oil is at least 0.01 ppm; and/or the total concentration of glycidyl fatty acid esters in the glyceride oil in the above aspects is at least 0.1 ppm.

19. A composition according to claim 18, wherein the total concentration of monochloropropanol and fatty acid esters thereof, in the glyceride oil is from 0.01 ppm to 30 ppm, from 1 ppm to 25 ppm, or from 1.5 ppm to 20 ppm; and/or wherein the total concentration of glycidyl fatty acid esters in the glyceride oil is from 0.1 ppm to 30 ppm, from 1 ppm to 25 ppm, or from 1.5 ppm to 20 ppm.

20. A composition according to claim 17, wherein the basic ionic liquid is choline bicarbonate or choline hydroxide.

Description

EXAMPLES

(1) General Method for Determination of Acid Value (Mg KOH/q of Oil) and FFA (Wt. %) Content of Glyceride Oil.

(2) To a beaker containing 60 ml of isopropyl alcohol was added 0.5 mL 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.

(3) To a glass vial was added 0.200 g 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.

(4) The Acid Value (mg KOH/g of oil) was subsequently calculated using the formula:
56.1NV/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.

(5) 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 3.17110.sup.5 mol (0.01/269). The amount of KOH required to neutralise this amount of oleic/palmitic acid (i.e. the Acid ValueAV) is calculated to be 2.086 mg of KOH/g of oil (3.17110.sup.556.1). Calculation of FFA content (wt. %) therefore has the following formula:
Wt. % FFA=Acid Value0.479
General Method for Ionic Liquid Treatment of Glyceride Oil.

(6) 1.5 g of refined oil sample is placed in a sample vial before being doped with a single dopant (e.g. chloropropanol, or fatty acid ester thereof, or glycidol, or fatty acid ester thereof). The resulting mixture is stirred for 3 h to ensure thorough mixing of the oil and dopant and the concentration of dopant in the oil is determined. Choline bicarbonate (100 mg, 80 w/w % in H.sub.2O supplied by Sigma-Aldrich UK) is added to the oil/dopant mixture and the resulting mixture stirred for approximately 12 h, either at room temperature or the lowest temperature at which the oil is in an entirely liquid state. The mixture is then centrifuged at 2500 rpm for 10 minutes. The upper oil phase is then removed and a small sample of the oil phase taken for analysis.

Example 1: Ionic Liquid Treatment of Butter

(7) The above general method was used as part of an ionic liquid treatment of a refined cow's milk butter comprising 20 wt. % water and less than 0.2 wt % FFA. The butter was heated to 40 C. to ensure it was in a liquid state before being doped with 3-MCPD obtained from Sigma-Aldrich. Results of oil analysis before and after the ionic liquid treatment are provided in Table 1 below.

Example 2: Ionic Liquid Treatment of Butter

(8) The above general method was used as part of an ionic liquid treatment of a refined cow's milk butter comprising 20 wt. % water and less than 0.2 wt % FFA. The butter was heated to 40 C. to ensure it was in a liquid state before being doped with 3-MCPD oleic acid ester obtained from Carbosynth Ltd UK. Results of oil analysis before and after the ionic liquid treatment are provided in Table 1 below.

Example 3: Ionic Liquid Treatment of Refined Corn Oil

(9) The above general method was used as part of an ionic liquid treatment of a refined corn oil comprising less than 0.2 wt % FFA. The oil was doped with 3-MCPD obtained from Sigma-Aldrich at room temperature. Results of oil analysis before and after the ionic liquid treatment are provided in Table 1 below.

Example 4: Ionic Liquid Treatment of Refined Corn Oil

(10) The above general method was used as part of an ionic liquid treatment of a refined corn oil comprising less than 0.2 wt % FFA. The oil was doped with 3-MCPD oleic acid ester obtained from Carbosynth Ltd UK. Results of oil analysis before and after the ionic liquid treatment are provided in Table 1 below.

Example 5: Ionic Liquid Treatment of Refined Olive Oil

(11) The above general method was used as part of an ionic liquid treatment of a refined olive oil comprising less than 0.2 wt % FFA. The oil was doped with 3-MCPD obtained from Sigma-Aldrich at room temperature. Results of oil analysis before and after the ionic liquid treatment are provided in Table 1 below.

Example 6: Ionic Liquid Treatment of Refined Olive Oil

(12) The above general method was used as part of an ionic liquid treatment of a refined olive oil comprising less than 0.2 wt % FFA. The oil was doped with 3-MCPD oleic acid ester obtained from Carbosynth Ltd UK. Results of oil analysis before and after the ionic liquid treatment are provided in Table 1 below.

(13) TABLE-US-00001 TABLE 1 Pre-IL treatment Post-IL treatment Example Dopant concentration (ppm) concentration (ppm) Ex. 1 3-MCPD 57684 16 Ex. 2 3-MCPD ester 9406 9331 Ex. 3 3-MCPD 644 52 Ex. 4 3-MCPD ester 7354 5109 Ex. 5 3-MCPD 3191 50 Ex. 6 3-MCPD ester 6871 3191

(14) The methodology used for analysis of the oils is that proposed by R. Weihaar, 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) 110, 183-186. This method involves cleavage of 3-MCPD fatty acid esters with sodium methoxide, extraction of 3-MCPD, derivatisation with phenylboronic acid and subsequent analysis using GC-MS (a deuterium-labelled internal standard (3-MCPD-d.sub.5) is also added to each sample).

(15) 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-d.sub.5) were the target ions. Ions at m/z 196 (3-MCPD) and m/z 201 (3-MCPD-d.sub.5) were the qualifiers. The detection limit of this methodology is 0.15 mg/kg.

(16) The above method may not distinguish between 3-MCPD esters and glycidyl fatty acid esters present in the oil. However, the concentration of each dopant used in the above examples is to such an excess relative to the concentration of glycidyl fatty acid esters in the oils tested (typically from 0.5 to 20 ppm in refined oils) that it is insignificant to the results of the analysis.

(17) The results of Table 1 demonstrate the advantages of the present invention. It is apparent that the ionic liquid treatment is capable of removing 3-MCPD from glyceride oil with high efficiency. For instance, the results of Example 1 show that even where a relatively large amount of 3-MCPD is doped into butter to give a 3-MCPD concentration of 57684 ppm, 3-MCPD is substantially eliminated following the ionic liquid treatmentreducing the 3-MCPD concentration to only 16 ppm. This starting concentration of 3-MCPD is substantially larger than would ever be expected with undoped crude and refined oils (for example, up to about 20 ppm). Similar results are also shown for the vegetable oils.

(18) The results of Table 1 also show that the ionic liquid treatment is capable of removing 3-MCPD fatty acid ester from glyceride oil. Reductions of 3-MCPD ester in corn and olive oils (Example 4 and 6) following the ionic liquid treatment are 31% and 54% respectively. The result for 3-MCPD ester removal from butter does not illustrate the same level of reduction. However, this result is believed to be impacted by the water content of the butter. Nevertheless, what is clear from the results is that the basic ionic liquid treatment would substantially eliminate all traces of 3-MCPD and 3-MCPD ester at the concentrations typically found in crude and refined glyceride oils.

(19) Furthermore, it is noteworthy that the refined oils treated in the above Examples had a low level of FFA. The results of Table 1 therefore also demonstrate that removal of 3-MCPD and 3-MCPD esters using the basic ionic liquid treatment does not rely on the acid-base reaction of the basic ionic liquid with FFA, or the formation of a quaternary ammonium-FFA salt.

Example 7: Ionic Liquid Treatment of Crude Palm Oil

(20) A sample (approximately 2 kg) of crude palm oil (CPO) having a measured FFA content of 3.8 wt. % was heated to 50 C. in a thermostatically controlled water bath. The homogeneous mixture of CPO was then added to a 2 L stirred tank reactor in which the reactor temperature was maintained at 50 C. by means of circulating heated oil. A stoichiometric amount of choline bicarbonate (80 wt. % in H.sub.2O supplied by Sigma-Aldrich UK) relative to the FFA content of the CPO was then introduced to the reaction vessel at a rate of 1-2 mL per minute. The reaction was stirred at 500 rpm using a mechanical overhead stirrer for 1 h. After reaction, the mixture was centrifuged at 4000 rpm for 3 minutes to separate a phase comprising quaternary ammonium-FFA salts and a treated CPO phase.

(21) The separated oil phase was titrated and found to contain 0.29 wt. % FFA. 3-MCPD fatty acid ester (3-MCPD-FA-Ester) content was determined before and after treatment with ionic liquid using standard method DGF-C-VI 18, Part A. Results are provided in Table 2 below.

(22) TABLE-US-00002 TABLE 2 Measurement Unit CPO Ex. 7 FFA content Wt. % 3.78 0.29 3-MCPD-FA-Ester mg/kg 0.2 0.1

(23) The results of Table 2 also demonstrate the advantages of the present invention. In particular, the results show that the basic ionic liquid treatment reduces the 3-MCPD ester concentration by 50% whilst also significantly reducing the FFA content of the oil. Removal of 3-MCPD ester is therefore not precluded by the presence of significant amounts of FFA, or by simultaneous neutralisation of FFA with the basic ionic liquid.

Example 8: Ionic Liquid Treatment of a Refined Palm Oil

(24) Five 30 g samples of commercially available refined, bleached and deodorized palm oil (RBDPO) having a measured FFA content of 0.1 wt. % were prepared and transferred to individual test tubes. Sample 8a was not doped with any additional material. Sample 8b was doped with 10 mg of 3-MCPD. Sample 8c was doped with 10 mg of 3-MCPD fatty acid ester (3-MCPD FA ester). Sample 8d was doped with 10 mg of glycidyl fatty acid ester (GE FA ester). Sample 8e was doped with 5 mg of 3-MCPD, 5 mg of 3-MCPD FA ester and 5 mg GE FA ester were added. The test tubes were sealed with parafilm and heated to 50 C. for 2 h in a thermostatically controlled oil bath.

(25) To each sample, choline bicarbonate (3 ml of 80 wt % in H.sub.2O solution) and H.sub.2O (2 mL) was added before the samples were stirred for 24 h at 50 C. The organic phase was separated. The combined 3-MCPD and 3-MCPD-FA ester content was determined for the commercially available RBDPO and for the organic phase of all 5 samples using the standard method DGF-C-VI 18, Part A. The GE-FA ester content was determined for the commercially available RBDPO and for the organic phase of all 5 samples using the standard method DGF-C-VI 18, Part B. Results are provided in Table 3 below.

(26) TABLE-US-00003 TABLE 3 Before treatment with IL After treatment with IL 3-MCPD-FA GE FA 3-MCPD-FA GE FA ester/3-MCPD ester ester/3-MCPD ester Sample (mg/kg) (mg/kg) (mg/kg) (mg/kg) 8a 2.6 4.3 0.5 1.3 8b 335.6.sup.1 4.3.sup.1 10.7 2.2 8c 335.6.sup.1 4.3.sup.1 21.6 1.5 8d 2.6.sup.1 337.3.sup.1 1.6 6.5 8e 334.6.sup.1 170.3.sup.1 22.5 1.1 .sup.1Calculated based on the weight of 3-MCPD, 3-MCPD-FA ester and/or GE-FA ester added and the measured amount of 3-MCPD-FA ester and GE-FA ester in the commercially available RBDPO.

(27) All samples show that the treatment of palm oil with choline bicarbonate ionic liquid leads to a reduction of the 3-MCPD/3-MCPD-FA ester and GE-FA ester content. Even with high amounts of 3-MCPD, 3-MCPD-FA ester and GE-FA ester, the ionic liquid is able to reduce their content significantly as shown in the results for samples 8b-8e. Furthermore, treatment of commercially available RBDPO reduces the 3-MCPD/3-MCPD-FA ester and GE-FA ester content by approximately 80% and 70%, respectively.