REDUCTION OF THE CONTENT OF GLYCIDYL ESTERS IN EDIBLE OILS

Abstract

A process of treating edible oil. An edible oil is brought in contact with porous bodies comprising an epoxide conversion catalyst. The porous bodies have a size of larger than 0.5 mm. A system for treatment of edible oil. The system comprises a first treatment unit and a reactor vessel arranged to receive edible oil originating from the first treatment unit. The reaction vessel comprises porous bodies comprising an epoxide conversion catalyst, the porous bodies having a size of larger than 0.5 mm. Use of porous bodies comprising an epoxide conversion catalyst, the porous bodies having a size of larger than 0.5 mm, for treatment of edible oil.

Claims

1. (canceled)

2. (canceled)

3. (canceled)

4. (canceled)

5. (canceled)

6. (canceled)

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16. (canceled)

17. A process for producing edible oil, comprising a step of passing a deodorized oil to a glycidyl ester conversion reactor for hydrolysis of an epoxide bond of a glycidyl ester in the presence of an acid catalyst, thereby reducing the amount of 3- and 2-monochloropropanediol (MCPD), 3- and 2-monochloropropanediol-fatty acid esters and glycidyl esters in the edible oil, wherein the hydrolysis is carried out by bringing the refined or modified edible oil in contact with a fixed bed of porous bodies larger than 0.5 mm comprising an acid catalyst comprising at least one of silica-alumina, alumina and gamma alumina.

18. The process according to claim 17, wherein the acid catalyst comprises silica-alumina.

19. The process according to claim 17, wherein the porous bodies are shaped bodies prepared by compacting or densifying particles comprising the acid catalyst.

20. The process according to claim 19, wherein the shaped bodies are pellets, extrudates, tablets or granules.

21. The process according to claim 17, wherein the refined or modified edible oil is brought in contact with the porous bodies at a temperature in the range of 60 C. to 150 C.

22. The process according to claim 17, wherein the refined or modified edible oil is brought in contact with the porous bodies at a temperature in the range of 40 C. to 120 C.

23. The process according to claim 17, wherein the refined or modified edible oil is brought in contact with the porous bodies at a temperature below 90 C.

24. The process according to claim 17, wherein the refined or modified edible oil is brought in contact with the porous bodies at a temperature between 40 C. to 60 C.

25. The process according to claim 17, wherein the refined or modified edible oil comprises palm oil, soybean oil, canola or rapeseed oil, sunflower oil, palm kernel oil, cottonseed oil, groundnut oil, corn or maize oil, olive oil, rice bran oil, cocoa butter, coconut oil, safflower oil, animal fats, such as tallow, lard or fish oil, or mixtures thereof.

26. The process according to claim 25, wherein the refined or modified edible oil comprises palm oil.

27. The process according to claim 17, wherein the refined or modified edible oil after having been in contact with the porous bodies is further refined.

28. The process according to claim 17, wherein the refined or modified edible oil after having been in contact with the porous bodies is further refined by being deodorized or steam stripped.

29. The process according to claim 28, wherein the refined or modified edible oil after having been in contact with the porous bodies is further refined by steam stripping by counter-current thin-film stripping.

30. The process according to claim 17, wherein the refined or modified edible oil is brought in contact with the porous bodies at a temperature in the range of 80 C. to 120 C., more preferably 90 to 110 C.

31. The process according to claim 17, wherein the refined or modified edible oil is brought in contact with the porous bodies at a temperature in the range of 90 C. to 110 C.

32. The process according to claim 17, wherein the refined or modified edible oil is brought in contact with the porous bodies at a temperature in the range of 50 C. to 90 C.

33. A system for producing an edible oil comprising a deodorizer and downstream of the deodorizer an apparatus for reducing the amount of 3- and 2-monochloropropanediol (MCPD), 3- and 2-monochloropropanediol-fatty acid esters and glycidyl esters in the refined or modified edible oil, said apparatus comprising a reaction vessel comprising a fixed bed of porous bodies larger than 0.5 mm comprising an acid catalyst comprising at least one of silica-alumina, alumina and gamma alumina, the system further comprising a second treatment unit arranged to receive the refined or modified edible oil originating from the reaction vessel, wherein the second treatment unit is a refining unit, such as a deodorizer or a steam stripper, preferably a steam stripper, more preferably a counter-current thin-film stripper.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 represents a system according to the invention at the tail end of a deodorizing section.

[0030] FIG. 2 represents a system according to the invention integrated in an advanced deodorization section.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0031] In FIG. 1, edible oil from a bleaching section (not shown) is passed to a deodorization section 10. Deodorized edible oil containing an elevated level of glycidyl esters exits the deodorization section 10 and is passed via a heat exchanger 20 and a pre-filter 30 to a glycidyl ester conversion reactor 40. Edible oil containing a reduced level of glycidyl esters exits the glycidyl ester conversion reactor 40 and is passed via a post-filter 50, re-heating to a suitable deodorization temperature (not shown) and a post-stripper 60 towards heat exchange economising (not shown), final cooling (not shown) and storage or packaging (not shown). Downstream a heat recovery step (not shown) of the deodorization section 10 the temperature of the oil coming from the deodorization section would typically be in the range of 120 to 140 C. During such heat recovery step, or just after it, it is common practice to add about 20 ppm of citric acid to the oil, e.g. by means of a 100 ppm to 20 wt % aqueous solution of citric acid 70, to chelate metal traces and increase the stability of the oil during storage. The temperature of the water/oil mixture is adjusted in an economizer (not shown) and the heat exchanger 20 to the optimum reaction temperature, in the range of 60 to 150 C., before entering the glycidyl ester conversion reactor 40. The glycidyl ester conversion reactor 40 contains a fixed bed 41 of porous bodies comprising an epoxide conversion catalyst. The oil is mildly steam stripped in the post-stripper 60, to which steam 80 is provided and from where off-gases are brought to a scrubber (not shown) and a vacuum system (not shown). Generally, pumps required for fluid transport are not shown.

[0032] In FIG. 2, edible oil from a bleaching section (not shown) is passed through an advanced deodorization section 110. The advanced deodorization section 110 includes a deodorizer or pre-stripper 111 followed by a quench cooler 112 and a retention section 113. The oil is deodorized or pre-stripped in the deodorizer or pre-stripper 111, to which steam (not shown) is provided and from which off-gases are brought to a scrubber (not shown) and a vacuum system (not shown). Edible oil exiting the retention section 113 is passed via a heat exchanger 120 to a glycidyl ester conversion reactor 140. The glycidyl ester conversion reactor 140 contains a fixed bed of porous bodies comprising an epoxide conversion catalyst. The heat exchanger 120 provides the option of adjusting the temperature of the oil entering the glycidyl ester conversion reactor 140. An additional small amount of water 190 is added to the oil to drive hydrolysis of the glycidyl epoxides to a high conversion level. Edible oil exiting the glycidyl ester conversion reactor 140 is brought to post-stripping temperature in a re-heater 195, before being passed via a post-stripper 114, a heat recovery section 115 and a post-filter 116 of the advanced deodorizing section 110 towards final cooling (not shown) and storage or packing (not shown). The post-stripper 114 removes volatiles, such as free fatty acids and smell and taste components, from the edible oil. As shown, the glycidyl ester conversion reactor 140 and its accessories can conveniently be placed between the retention section 113 and the post-stripper 114 of the advanced deodorizing section 110. Generally, pumps required for fluid transport are not shown.

EXAMPLES

[0033] In the examples reported below, the glycidyl ester content was analysed according to the AOCS (American Oil Chemists' Society) Official Method Cd 29b-13, revised 2015. This method reports the glycidyl ester content as glycidol in mg per kg oil, i.e. in parts per million by weight, herein abbreviated as ppm. The limit of quantification is 0.1 ppm.

[0034] The following porous materials were employed in the examples reported below. [0035] A1 Bleaching earth Tonsil 112FF [0036] A2 Bleaching earth Tonsil 215FF [0037] B Gamma alumina [0038] C Silica-alumina [0039] D Aluminium hydroxide [0040] E Gamma alumina [0041] F Silica-alumina

[0042] Materials A1 and A2 were obtained from Clariant, Switzerland. Materials B to E were obtained from Haldor Topsoe A/S, Denmark.

[0043] Materials A1 and A2 are acid treated bleaching earths. Materials B, C, E and F are inherently acidic. Material D has no acidity.

[0044] The materials were employed in powder form suitable for suspension in oil as a slurry under agitation. Material C was additionally employed in form of pellets having a diameter of 1.6 mm and a length of 1 to 4 times the diameter. The pellets were prepared from the powder of material C by addition of a binder, extrusion of the mixture of powder and binder, and subsequent calcination of the extruded pellets. Further properties of the materials are provided, as specified by the supplier, in the table below (n/a=not available).

TABLE-US-00001 Pore volume % Pore Meso pore peak Material (cm.sup.3/g) volume > 250 () A1 n/a n/a n/a A2 0.38 30% n/a B 0.5-1 20% 30-80 C 0.5-0.75 20-30%.sup. 26-36 D .sup.0.3-0.5 20-30%.sup. 30-80 E 0.5-1 10% 30-80 F 0.5-1 20% 30-80 Specific area Ratio Material BET (m.sup.2/g) SiO.sub.2/Al.sub.2O.sub.3 A1 180 7.1 A2 230 4.6 B 200-450 0 C 200-450 0.9-1.3 D 200-450 E 200-450 0 F 200-450 2.0-2.5

Example 1. Screening for Glycidyl Epoxide Conversion Activity

[0045] Materials A1, A2, B, C, D and E, all in powder form, were screened for glycidyl epoxide conversion activity. Refined oil (palm olein) was treated by addition of 0.5 wt % of the respective material and mixing for 45 min at 110 C. Subsequently the slurry was filtered and oil was withdrawn for analysis.

[0046] Considering the glycidyl ester content of the palm olein before and after treatment, it was found that A1, A2 and C had the same high glycidyl epoxide conversion activity, whereas B and E showed medium activity and D no activity.

[0047] An indicative taste panel test was conducted (4 participants), giving marks for bland smell and taste. Higher marks being given for a blander smell and taste, the results were untreated refined oil>oil treated with B, C, D or E>materials treated with A1 or A2. These results suggested that fewer undesirable side-reactions appear to take place with the alternatives to conventional bleaching earth or, in other words, that less post-treatment appears to be required for such alternatives.

[0048] We therefore concluded that it is possible to find alternatives to bleaching earth for high conversion of glycidyl epoxides.

Example 2. Performance of Epoxide Conversion Catalyst Bodies as Acid Catalyst

[0049] A pilot plant was established operating on a side stream from an industrial unit producing refined, bleached and deodorized palm olein. The pilot plant as well as the industrial unit was manufactured from stainless steel 316. Oil at a temperature of about 120 C. came from a heat recovery step (vacuum heat exchanger, VHE, operated under gravity flow and simultaneous agitation and steam addition) in the deodorization section of the industrial unit. In the VHE 100 ppm citric acid solution had been added to the oil. A side stream was withdrawn at a pressure of about 3.6 barg and sent to a 10 micron bag filter for collection of particles (such as undissolved citric acid or citric acid chelated metals), in this way protecting the subsequent catalyst bed. The temperature of the withdrawn oil was increased to a temperature of 140 C. by an in-line heating element. A needle valve was used to control the flow rate. The oil then entered a reactor with a diameter of 56 mm and a height of 1000 mm. 1.3 kg of porous bodies of material C, formed as 1.6 mm diameter extruded cylinders, were loaded in the reactor.

[0050] At 140 C. and a flow rate of 2.6 litres of oil per hour, no glycidyl esters could be detected in the product oil (i.e. glycidyl ester content was below detection limit of 0.1 ppm, reported as glycidol). Furthermore, no significant increase was observed in the free fatty acid level. Even when the oil flow rate was increased to 15 litres of oil per hour, still at 140 C., no glycidyl esters could be detected. Neither could any significant increase in free fatty acid level be detected. With a density of the oil of about 0.85 kg/litre, the latter reaction conditions correspond to an oil/catalyst ratio of 15*0.85/1.3=10.

[0051] The usual consumption of bleaching clay in conventional slurry treatment of oil is in the range of 0.1-0.5 wt % of the treated oil. With the demonstrated ability to process 10 kg oil/kg catalyst per hour, we only need to process 200 kg oil (i.e. operate for 20 hours) to reach break-even with a 0.5 wt % bleaching earth operation or to process 1000 kg oil (i.e. operate for 100 hours) to reach break-even with a 0.1 wt % bleaching earth operation.

[0052] Some smell and taste changes were noted for the treated oil. It cannot be excluded that some of the changes come from overheating the oil due to an imperfect heater used, periods of non-operation where the oil has had long residence time in contact with hot metal surfaces, and/or long eluation times for such destroyed oil. Such smell and taste changes were, however, expected to be dealt with in a subsequent mild steam stripping processing step.

Example 3. Organoleptic Properties of Rapeseed Oil

[0053] Materials A2 (powder), C (powder and pellets with a diameter of 1.6 mm) and F (powder) were tested to compare impact on smell and taste of refined rapeseed oil. The test procedure was as follows.

1. Take about 90 grams (100 ml) of refined rapeseed oil.
2. Heat to about 100 C. in a micro-wave oven and maintain temperature on a heating plate.
3. Dose 0.2% water under agitation.
4. Dose 0.5% of powder material (A2, C, F); or 5% of pellet material (C) under agitation.
5. Keep stirring for about 20 minutes.
6. Filter and re-filter the mixture on filter paper equipped on Buchner funnel placed on top of vacuum flask.
7. Collect filtered oil in 100 ml plastic bottle.
8. Heat filtered oil to about 40 C. on water bath and test for smell and taste (panel test with 5 participants).

[0054] Untreated refined rapeseed oil was considered as a reference sample having a bland smelling and an acceptable taste. Oil treated with material A2 was smelling and tasting bad. Oils treated with material C (powder or pellets) or F came out almost equal, having a better taste and smell than oil treated with material A2 but not as good as the reference sample. Oil treated with material C (pellets) was relatively bland in taste, though not neutral. Oil treated with material F did exhibit a slightly different smell compared to oils treated with material C (powder or pellets).

[0055] It was considered likely that mild deodorisation of oils treated with material C (powder or pellets) or F should easily and efficiently remove contained odoriferous compounds.

Example 4. Glycidyl Epoxide Conversion and Subsequent Deodorization

[0056] For a semi-industrial demonstration, a catalyst in the form of a silica-alumina with an acidic catalytic function (material C) was selected. It was used as porous, extruded pellets, with a pellet diameter of 1/16 inch (1.6 mm). 47.5 kg catalyst was loaded in a fixed bed reactor. Bleached and deodorized palm oil with a glycidyl ester content of 3.4 ppm was fed to the reactor at a feed rate of 1 ton/hour at 110 C. It was found that the glycidyl ester content in the treated oil was 0.14 ppm, reported as glycidol. A total of 25 tons of palm oil was treated in this way and accumulated in a tank. Samples of the oil withdrawn after the reactors showed unacceptable organoleptic properties (taste, smell).

[0057] Subsequently the accumulated oil was fed to a batch deodorizer. Deodorization took place at 220 C. for 40 minutes. After deodorization the organoleptic properties were found to fulfil the product requirement in a panel test. The glycidyl ester content was 0.37 ppm, reported as glycidol, after the deodorization.