A PROCESS FOR REDUCING GLYCIDYL ESTERS IN MONOGLYCERIDES COMPRISING MONOUNSATURATED MONOGLYCERIDES

Abstract

 The present invention relates to a process for reducing the level of glycidol and/or glycidyl esters in a preparation of monoglycerides wherein said monoglycerides are prepared by transesterification between glycerol and triglycerides, said triglycerides comprising 10-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-90% saturated aliphatic fatty acid esters or by direct esterification between glycerol and fatty acids, said fatty acids comprising 10-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-90% saturated aliphatic fatty acids, The process comprises at least one holding step in which said preparation of monoglycerides and diglycerides is maintained at a temperature in the range of 140-210°C for a period of time (the holding time) in the range of 10-90 minutes in a separate temperature controlled unit followed by a distillation step.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a process for reducing the level of glycidol and glycidyl esters in preparations of monoglycerides prepared by transesterification between glycerol and triglycerides, said triglycerides comprising 10-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-90% saturated aliphatic fatty acid esters or by direct esterification between glycerol and fatty acids, said fatty acids comprising 10-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-90% saturated aliphatic fatty acids.

BACKGROUND OF THE INVENTION

[0002] Glycidol and glycidyl esters are formed during high temperature processing of materials containing tri-, di- or monoglycerides or glycerol. Glycidol is classified as a genotoxic carcinogen (IARC 2000 and COMMISSION REGULATION (EU) 2018/290 of 26 February 2018) and consequently it is desirable to provide a method of reducing the level of glycidol and glycidyl esters in products containing these compounds.

[0003] Several solutions to the problem of reducing or eliminating the contamination of edible oils and fats with glycidol and glycidyl esters have been proposed in the art.

[0004] WO 2011/069028 discloses several methods of removing glycidyl esters from an oil, including contacting the oil with an absorbent and subsequently steam refining the oil; contacting the oil with an enzyme and subsequently steam refining the oil; deodorizing the oil at a temperature not exceeding 240°C; contacting the oil with an acid solution; rebleaching the oil, etc.

[0005] US 2014/0357882 discloses a process of reducing the content of glycidyl esters in vegetable oils using an acid-activated bleaching earth as an absorbent and deodorizing the oil at less than 200°C for at least 30 minutes.

[0006] WO 2012/031176 discloses a process for reducing glycidol from oils using a carboxylate anion and cation counterion to react with glycidol.

[0007] WO 2016/189328 discloses a process for removing glycidol and glycidyl esters from glyceride oils by treatment with a basic ionic liquid.

[0008] WO 2014/012759 discloses a process for reducing the amount of MCPD and glycidol in triglyceride oils by bleaching the oil with a base while passing steam through the oil at reduced pressure.

[0009] EP 2471897 discloses a process for reducing MCPD and glycidyl esters from oils, for instance by treating deodorized oils with silica gel and/or alkaline activated carbon or by mixing the oil with an organic acid aqueous solution and dehydrating at 50-180°C under reduced pressure.

[0010] Shimizu, M. et. al.; J. Am. Oil Soc. (2013), 90,1449-1454 discloses Temperature Dependency When Generating Glycidyl and 3-MCPD Esters from Diolein'.

[0011] Monoglycerides are widely used as emulsifiers in the food industry. They are typically prepared by transesterification between glycerol and triglycerides or by direct esterification between glycerol and fatty acids. The esterification or transesterification are carried out at elevated temperatures such as temperatures above 230°C, in the presence of a catalyst, such as a base, for example a carboxylate ion. The product from the direct esterification or transesterification reaction is a blend of mono-, di- and tri-glycerides and glycerol. Glycerol is removed by processes such as stripping or centrifugation at a lower temperature such as for example 180°C. Monoglycerides may be separated or concentrated from diglycerides and triglycerides by operations such as vacuum short path distillation, such as at temperatures above 210°C.

[0012] The functional groups of the monoglyceride and diglyceride molecules foster glycidol and glycidyl ester formation by several potential reaction mechanisms illustrated below (wherein R represents an alkyl or alkenyl group), particularly when submitted to temperatures above 220°C. Consequently, the glycidyl ester formation is especially high during the transesterification and direct esterification process; and furthermore, substantial glycidyl ester formation is expected during the high temperature distillation process to obtain distilled monoglycerides.

[0013] One possible pathway for glycidyl ester formation is during the 1,2-rearrangement that constantly takes place within the monoglyceride molecule. The fatty acid can change position by acyl migration between the C₁ and C₂-atoms. During the transition state water is eliminated from the intermediate as shown in reaction scheme I, thereby forming an epoxide ring at the neighbouring C-atoms.

[0014] A second possible pathway for glycidyl ester formation is during the elimination of a fatty acid from a diglyceride as shown in reaction scheme II. The elimination results in a transition state similar to that of the pathway shown in scheme I, from which the epoxide ring can form.

[0015] A third possible pathway for glycidyl ester formation is via formation of glycidol from glycerol as shown in reaction scheme III. The formed glycidol reacts with a triglyceride or free fatty acid in the same way as glycerol does. The catalyst is the same as in the direct esterification or transesterification process, i.e. a carboxylate ion or base.

[0016] The epoxide ring in glycidol and glycidyl esters is highly reactive and under certain reaction conditions it may react with any molecule containing a hydroxyl group (e.g. a hydroxyl group in water, glycerol, monoglyceride) resulting in the opening of the epoxide ring and converting the glycidyl ester as shown in reaction schemes IV below.

[0017] It would be desirable to provide cost-effective and efficient procedure for reducing the level of glycidol and glycidyl esters formed when producing monoglycerides. Furthermore, it would be desirable to provide a procedure which would result in only an insignificant decrease of the content of monoglycerides.

SUMMARY OF THE INVENTION

[0018] It has been found that keeping preparations of mono- and/or di-glycerides at temperatures below 210°C may reduce the level of glycidol and/or glycidyl esters. The reduction rate and the final level of glycidol and glycidyl esters depend on the temperature applied. Mono- and diglycerides degrade on prolonged heat exposure and the optimal treatment time and temperature for reducing the level of glycidol and glycidyl esters is a balance between an efficient reduction of glycidol and glycidyl esters and an acceptable level of degradation of mono- and diglycerides.

[0019] Thus, it has been found that the level of glycidol and/or glycidyl esters are reduced when reaction products from transesterification between glycerol and triglycerides or direct esterification between glycerol and fatty acids are maintained at a temperature in the range of 140-210°C for a period of time (the holding time) in the range of 10-90 minutes in a temperature-controlled unit.

[0020] Furthermore, it has surprisingly been found that subsequent distillation wherein monoglycerides, which have been prepared by transesterification between glycerol and triglycerides, said triglycerides comprising 10-100% mono-unsaturated aliphatic fatty acid esters, 0-10% poly-unsaturated aliphatic fatty acid esters and 0-90% saturated aliphatic fatty acid esters or by direct esterification between glycerol and fatty acids, said fatty acids comprising 10-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-90% saturated aliphatic fatty acids, are concentrated from diglycerides and triglycerides leads to a reduced level of glycidol and/or glycidyl ester in the distilled monoglycerides or does not lead to a significantly increased level of glycidol and/or glycidyl ester or compared to the level of glycidol and/or glycidyl ester of the product mixture prior to distillation.

[0021] Accordingly, the present invention relates to a process for reducing the level of glycidol and/or glycidyl esters in a preparation of monoglycerides, wherein said monoglycerides are prepared by transesterification between glycerol and triglycerides, said triglycerides comprising 10-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-90% saturated aliphatic fatty acid esters or by direct esterification between glycerol and fatty acids, said fatty acids comprising 10-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-90% saturated aliphatic fatty acids, said process comprising (a) a holding step in which reaction products from said transesterification or direct esterification are maintained at a temperature in the range of 140-210 °C for a period of time (the holding time) in the range of 10-90 minutes in a separate temperature-controlled unit, (b) a distillation step for purification of said monoglycerides, wherein the distillation step is carried out after the holding step.

DETAILED DESCRIPTION OF THE INVENTION

[0022] In an embodiment of the invention the process comprises (a) a holding step in which reaction products from said transesterification or direct esterification are maintained at a temperature in the range of 140-210°C for a period of time (the holding time) in the range of 10-90 minutes in a separate temperature-controlled unit, (b) a glycerol removal step, (c) a distillation step for purification of said monoglycerides, wherein the distillation step is carried out after the holding step and the glycerol removal step.

[0023] It has been found important to maintain the temperature of the holding step at a level that provides maximum reduction of the level of glycidol and glycidyl esters and at the same time leads to the least degradation of the monoglycerides.

[0024] In a currently favoured embodiment of the present process, the temperature of the holding step prior to the distillation step is therefore in the range of 170-200°C, such as 175-200°C, such as 180-195°C, such as 184-194°C, or such as 185-190°C.

[0025] The holding time for the holding step prior to the distillation step is preferably in the range of 10-90 minutes, such as 20-80 minutes, such as 20-60 minutes, such as 25-50 minutes, such as 25-40 minutes, such as about 30 minutes.

[0026] In an embodiment of the invention the process comprises a second holding step wherein the distilled monoglycerides after optional glycerol removal and after distillation are maintained at a certain temperature and for a certain period of time (the holding time) in a temperature-controlled unit.

[0027] In an embodiment of the invention the temperature of the second holding step is in the range of 140-200°C, such as 140-190°C, such as 140-180°C, such as 150-175°C, such as 150-170°C, such as 155-175°C, such as 160-170°C, such as about 160°C or such as about 170°C and the holding time is in the range of 10-90 minutes, such as in the range of 20-70 minutes, such as 25-80 minutes, such as 30-65 minutes, such as 30-60 minutes, such as 30-40 minutes, such as about 35 minutes or such as about 30 minutes.

[0028] In another embodiment of the invention the temperature of the second holding step is in the range of 70-130°C, such as in the range of 75-125°C, such as 80-120°C, such as 80-100°C, such as 85-110°C, such as 85-95°C, such as about 90°C and the holding time is in the range of 1-14 days, such as 1-10 days, such as 1-6 days, such as 2-6 days, such as 2-5 days, such as 2-4 days, such as about 3 days.

[0029] In yet another embodiment of the invention, the present process comprises a third holding step wherein the monoglycerides and/or diglycerides are maintained at a temperature in the range of 70-130°C for a period of time (the holding time) in the range of 1-14 days. The temperature of the third holding step is suitably in the range of 70-130°C, such as in the range of 75-125°C, such as 80-120°C, such as 80-100°C, such as 85-110°C, such as 85-95°C, such as about 90°C. The holding time for the third holding step is in the range of 1-14 days, such as 1-10 days, such as 1-6 days, such as 2-6 days, such as 2-5 days, such as 2-4 days, such as about 3 days.

[0030] The second and/or third holding step may favourably be carried out after the distillation step in which monounsaturated monoglycerides are concentrated from diglycerides and triglycerides.

[0031] In one embodiment of the present process, the temperature-controlled unit suitable for use in the holding step(s) may be a plug flow reactor, packed column, tray column or stirred tank reactor (continuous, semi-batch or batch) or similar equipment which may provide a specified residence time at a specified temperature to the material. The temperature may suitably be controlled by a heat transfer jacket on the temperature-controlled unit, an internal heating coil inside the temperature-controlled unit, heat exchangers in the feed-flow pipe or a combination of the different heating sources.

[0032] In an embodiment of the invention the temperature-controlled unit used in a holding step carried out prior to the distillation step is a plug flow reactor, packed column, tray column or continuous or batch stirred tank reactor.

[0033] In an embodiment of the invention the temperature-controlled unit used in a holding step carried out after the distillation step is a tray column or a plug flow reactor.

[0034] In an embodiment of the invention the temperature-controlled unit used in the second or third holding step is a batch tank reactor.

[0035] The starting material for preparing the monoglycerides and/or diglycerides may be a vegetable or animal oil, fat or fatty acids. Fats and oils are mixtures of acyl glycerides with triglycerides as the predominant species although they may also contain mono- and diglycerides as well as free fatty acids. The fat or oil for transesterification may suitably be selected from edible oils and fats such as palm oil, sunflower oil, corn oil, soybean oil, safflower oil, peanut oil, rapeseed oil, grape kernel oil, cottonseed oil, coconut oil, rice bran oil, olive oil, lard, tallow or castor oil. The fats and oils maybe refined, fully hydrogenated, partially hydrogenated or selectively hydrogenated and/or blended. The combined oils, fats or blends for use in the transesterification of the present invention comprise 10-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-90% saturated aliphatic fatty acid esters.

[0036] In an embodiment of the invention the combined oils, fats or blends for use in the transesterification of the present invention have a fatty acid ester content consisting of 10-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-90% saturated aliphatic fatty acid esters.

[0037] In an embodiment of the invention the combined oils, fats or blends for use in the transesterification of the present invention comprise 20-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-80% saturated aliphatic fatty acid esters; such as 25-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-75% saturated aliphatic fatty acid esters; such as 30-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-70% saturated aliphatic fatty acid esters, such as 35-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-65% saturated aliphatic fatty acid esters; such as 40-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-60% saturated aliphatic fatty acid esters; such as 50-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-50% saturated aliphatic fatty acid esters; such as 60-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-40% saturated aliphatic fatty acid esters.

[0038] Fatty acids are usually produced by hydrolysing acyl glycerides from fats and oils. The fatty acids for direct esterification may suitably be selected from edible oils and fats such as palm oil, sunflower oil, corn oil, soybean oil, safflower oil, peanut oil, rapeseed oil, grape kernel oil, cottonseed oil, coconut oil, rice bran oil, olive oil, lard, tallow or castor oil; and the oils maybe refined, fully hydrogenated, partially hydrogenated or selectively hydrogenated before hydrolysing to retrieve the free fatty acids. The fatty acids maybe also be refined, fully hydrogenated, partially hydrogenated or selectively hydrogenated, and they may be separated into the pure fatty acid types and may be blended. The combined fatty acids for use in the esterification of the present invention comprise 10-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-90% saturated aliphatic fatty acids. In an embodiment of the invention the combined fatty acids for use in the esterification of the present invention consist of 10-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-90% saturated aliphatic fatty acids.
In an embodiment of the invention the combined fatty acids for use in the esterification of the present invention comprise 20-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-80% saturated aliphatic fatty acids; such as 25-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-75% saturated aliphatic fatty acids; such as 30-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-70% saturated aliphatic fatty acids, such as 35-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-65% saturated aliphatic fatty acids; such as 40-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-60% saturated aliphatic fatty acids; such as 50-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-50% saturated aliphatic fatty acids; such as 60-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-40% saturated aliphatic fatty acids.

[0039] The monoglycerides and diglycerides prepared by transesterification or direct esterification are of the general Formula 1:

wherein one or two of R₁, R₂ and R₃ is an acyl group and the remaining one or two of R₁, R₂ and R₃ are hydrogen. The acyl groups have saturated or unsaturated, aliphatic chains with chain lengths of C₇-C₂₃. It is understood that the monoglycerides present in the preparation may comprise a mixture of monoglycerides with a variety of acyl chains.

[0040] The monoglycerides in the preparation are of the general Formula 1,
wherein one of R₁, R₂ and R₃ is a C₈-C₂₄ aliphatic acyl group and the remaining two of R₁, R₂ and R₃ are hydrogen. In an embodiment of the invention the combination of acyl groups comprises 10-90% mono-unsaturated aliphatic C₇-C₂₃ chains, 0 -5% poly-unsaturated aliphatic C₇-C₂₃ chains and 0-90% saturated aliphatic C₇-C₂₃ chains. It is understood that the monoglycerides present in the preparation may comprise a mixture of monoglycerides with a variety of acyl chains.

[0041] The preparation of concentrated or distilled monoglycerides may contain up to 15% diglycerides, such as up to 12%, 10%, 8% or up to 5% diglycerides.

[0042] In an embodiment of the invention it has been found possible to obtain more than 90% reduction of the level of glycidol and glycidyl esters relative to the level of glycidol and glycidyl esters present in the reaction mixture of the transesterification or direct esterification, preferably in more than 93% w/w reduction, more preferably more than 95% w/w reduction, such as from 95% w/w to 99% w/w reduction, relative to the level of glycidol and glycidyl esters present in the reaction mixture of the transesterification or direct esterification.

[0043] In an embodiment of the invention glycerol is removed by processes such as stripping or centrifugation or distillation prior to the distillation of monoglycerides.

[0044] In an embodiment of the invention the distillation step is performed as a vacuum short path distillation, such as at temperatures above 230°C, such as above 220°C, such as above 210°C, such as above 200°C. During the distillation step monoglycerides are separated or concentrated from glycerol, diglycerides and/or triglycerides from the direct esterification or transesterification step.

[0045] The level of glycidol and glycidyl esters in the mono- and diglyceride preparations was determined by a method based on DGF (Deutsche Gesellschaft für Fettwissenschaft) standard method C-III 18 (09). In this method, acyl groups are cleaved off leaving glycerol, glycidol and monochloropropanediol (MCPD) that are subjected to GC-MS analysis. According to the method, an excess of NaCl is added, causing the glycidol to react with the chlorine atom thereby being converted to MCPD which is therefore the compound measured in the GC-MS analysis. It has been found, however, that the quantity of MCPD and MCPD esters in the samples is very low and that for all practical purposes it could be ignored.

[0046] The present invention is described in further detail in the following examples which are not in any way intended to limit the scope of the invention as claimed.

EXAMPLES

Example 1

[0047] The reaction mixtures from transesterifications with glycerol and various triglycerides at 240°C were treated in a full-scale plug flow reactor at a holding temperature of 190°C (average temperature through the column) and with a holding time 30 minutes. Afterwards, the treated reaction mixture was stripped of glycerol by a stripping column, and the monoglycerides were distilled in a vacuum short path distillation column at average jacket temperatures between 228-249°C, to obtain a distilled product having a monoglyceride content of more than 90%. The combined glycidol and glycidyl ester content was measured in the product after each processing step and the percentage-wise reduction of glycidol and glycidyl ester (GE) content during each processing step was calculated. Results are shown in Table 1.

Table 1

Example No.	Triglyceride	Content of mono-unsaturated (MS) and poly-unsaturated (PS) fatty acid esters and saturated (S) fatty acid esters	Glycidol and GE reduction during plug flow reactor treatment	Glycidol and GE reduction during stripping of glycerol	Glycidol and GE reduction during distillation step	Total glycerol and GE reduction during plug flow reactor treatment, stripping of glycerol and distillation step
1	Selectively hydrogenated rapeseed oil	MS: 69-88%	74%	33%	97%	99%
2	Selectively hydrogenated rapeseed oil	PS: 0-5%	78%	17%	91%	98%
3	Selectively hydrogenated rapeseed oil	S: 7-31%	79%	33%	91%	99%
4	Palm oil	MS: 36-44%	76%	37%	87%	98%
5	Palm oil	PS: 7-13%	74%	38%	88%	98%
6	Palm oil	S: 43-57%	75%	41%	85%	98%
7	Selectively hydrogenated soybean oil	MS: 67-85%	75%	40%	69%	95%
		PS: 0-5%
		S: 10-33%
A	Fully hydrogenated palm oil	MS: 0-2%	78%	37%	-172%	63%
		PS: 0-1%
		S: 97-100%

[0048] Examples 1-7 are examples of the present invention.

[0049] Comparative Example A, which is not an example claimed by the present invention, describes preparation of monoglycerides from saturated triglycerides.

[0050] Examples 1-7 and Comparative Example A shows that the glycidol and glycidyl ester content in a transesterification product of triglycerides is reduced during the holding step and the stripping step.

[0051] Examples 1-7 show that the glycidol and glycidyl ester content is reduced profoundly during the distillation step; whereas Comparative Example A disclose a profound increase in glycidol and glycidyl ester content during the distillation step.

Claims

1. A process for reducing the level of glycidol and/or glycidyl esters in a preparation of monoglycerides, wherein said monoglycerides are prepared by transesterification between glycerol and triglycerides, said triglycerides comprising 10-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-90% saturated aliphatic fatty acid esters, or by direct esterification between glycerol and fatty acids, said fatty acids comprising 10-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-90% saturated aliphatic fatty acids, said process comprising

(a) a holding step in which reaction products from said transesterification or direct esterification are maintained at a temperature in the range of 140-210°C for a period of time (the holding time) in the range of 10-90 minutes in a separate temperature-controlled unit,

(b) a distillation step for purification of said monoglycerides, wherein the distillation step is carried out after the holding step.

2. The process according to claim 1, said process comprising

(a) a holding step in which reaction products from said transesterification or direct esterification are maintained at a temperature in the range of 140-210°C for a period of time (the holding time) in the range of 10-90 minutes in a separate temperature-controlled unit,

(b) a glycerol removal step,

(c) a distillation step for purification of said monoglycerides, wherein the distillation step is carried out after the holding step and the glycerol removal step.

3. The process according to claim 1 or claim 2, wherein the triglycerides comprise 30-100% mono-unsaturated aliphatic fatty acid esters, 0-15% poly-unsaturated aliphatic fatty acid esters and 0-70% saturated aliphatic fatty acid esters, or wherein the fatty acids comprise 30-100% mono-unsaturated aliphatic fatty acids, 0-15% poly-unsaturated aliphatic fatty acids and 0-70% saturated aliphatic fatty acids.

4. The process according to any one of claims 1-3, wherein the temperature of the holding step in the range of 170-200°C.

5. The process according to any one of claims 1-4, wherein the holding time in the holding step is in the range of 20-45 minutes.

6. The process according to any one of claims 1-5 comprising an additional holding step wherein the monoglycerides are kept at a temperature in the range of 140-200°C for a period of time in the range of 10-90 minutes, and wherein said additional holding step is carried out after a distillation step.

7. The process according to claim 6, wherein the temperature of the additional holding step is in the range of 140-180°C.

8. The process of any one of claims 6-7, wherein the holding time in the additional holding step is in the range of 25-80 minutes.

9. The process according to any one of claims 1-8 comprising an additional holding step wherein the monoglycerides are kept at a temperature in the range of 70-130°C for a period of time in the range of 1-14 days, wherein said holding step is carried out after the distillation step.

10. The process according to claim 9, wherein the temperature of the additional holding step is in the range of 80-100°C.

11. The process of claims 8-9 wherein the monoglycerides are kept for a period of time in the range of 2-6 days.

12. The process according to any one of claims 1-11, wherein the temperature-controlled unit used in a holding step is a plug flow reactor, packed column, tray column, continuous stirred tank reactor or batch stirred tank reactor.

13. The process according to any one of claims 1-12, wherein the monoglycerides are of the general 1:

wherein one of R₁, R₂ and R₃ is an acyl group and the remaining two of R₁, R₂ and R₃ are hydrogen, wherein said acyl groups comprise 10-100% mono-unsaturated aliphatic C₇-C₂₃ chains, 0-5% poly-unsaturated aliphatic C₇-C₂₃ chains and 0-90% saturated aliphatic C₇-C₂₃ chains.

14. The process according to any one of claims 1-13, wherein the level of glycidol and glycidyl esters in the distilled monoglycerides is reduced by more than 90% relative to the level of glycidol and glycidyl esters present in the preparation obtained by transesterification between glycerol and triglycerides or by direct esterification between glycerol and fatty acids.