FIELD OF THE INVENTION

The present invention relates to a process for producing a refined vegetable oii.

BACKGROUND OF THE INVENTION

Free 3~monochSoropropane- 1,2 -dio! (3-MCPD} has been identified as a contaminant, in various foods like liquid seasoning (e.g. soy sauce) and bakery products that have been heated to high temperatures. This substance is formed when fat- and chloride salt-containing foods are processed at high temperatures.

Studies have identified 3-MCPD fatty acid esters in refined oils, such as refined palm oil. 3-MCPD fatty acid esters are believed to be formed at high temperatures in the presence of water following a reaction between fats and chloride ions. In the refining of palm fruit, oii and fractions of palm fruit oils, 3-MCPD fatty acid esters are believed to be formed predominantly during deodorisation, the last stage in refining wherein undesirable odorous and taste-bearing substances are removed. Besides 3-MCPD fatty acid esters, 2-MCPD fatty acid esters and glycidyl fatty acid esters have also been identified in these refined palm fruit oils.

Processing techniques tha minimise formation of the 3-MCPD fatty add esters during the refining of crude palm fruit oil products have been suggested in the prior art. EP 27.16746 Al describes a method for producing crude palm oil from which free chlorine (which is a substance causing formation of 3-monochioropropane-l,2 ^» dtol (3-MCPD) fatty acid esters) is removed before the refining process via washing with water such uitra-pure water, distiiled water, and/or defonized water, which contains no chlorine ions which enables the suppression of formation of 3-MCPD esters. This method produces crude palm oii with free chiorine content of 2ppm or less and refined palm oil produced has a content of 3-MCPD fatty acid esters of 1 g/kg or less.

EP 2471897 Al describes a method for reducing chloropropanols and a formative substance in bieached and deodorized palm oil with silica gel and reducing a giycidol fatty acid ester via ascorbic acid (organic acid) which produces content of chioropropanols and a formative substance in the refined palm oil of 4 ppm or less,

WO 2011009843 Al describes the process of purifying palrn oil / palm stearin pa!m oil with an inert gas (i.e. nitrogen} and a deodorization step for removing off-taste and off-odours to limit the formation of HCPD in the oil. A food product comprising of this deodorized oil should contain less than 950 pg of bound 3-MCPD per kg of extracted fat. WO2012169718A1 describes a method of removing chlorine ions from tap water used in the refining process after the degumming, deoxidizing, bleaching and deodorizing processes. The edible oil manufactured will have a content of 3-MCPD of 0.3 ppm or less. EP 2502500 Al describes a process to produce refined piant oil free of chlorinated contaminants from crude piant oil with use of liquid-liquid extraction with a polar solvent solution and a pre-treatment step of washing crude oil with acid. This process produces refined piant oil with HCPD content less than 1 ppm or preferably less than 03 ppm.

There remains a need in the art to provide a refined vegetabie oi! with reduced 3- MCPD fatty acid esters and Sow chlorine content t address the abov problems, or at least to provide an alternative.

SUMMARY OF THE INVENTION

Th present invention provides a process of refining crude palm fruit oil that yields a refined vegetable oil having a iow content of S- onocbloropropane-i^-dlol (3~ MCPD) and a low chlorine content. The present invention relates to a process for producing refined vegetable oil, the process including the steps of:

a. heating a crude vegetable oii at temperatures between 55°C to 95°C to produce a heated crude vegetable oil;

b. providing between G.5w/w to 1.0 w/w of a dechiorination agent to the heated crude vegetable oil to produce a deehiorinated vegetable oil, wherein the dechiorination agent is selected from sodium metabisulfite, sodium bisulfite, sodium thiosulfate, sulfur dioxide,, sodium ascorbate, hydrogen peroxide, sodium nitrite, sodium sulphite, calcium thiosulfate or any combination thereof for a dechlorination period of between 1 to 50 days;

c. filtering the deehiorinated vegetable oil to remove the dechlorination agent;

d. degumming of the deehiorinated vegetable oil with organic acids at the temperature range between S5°C to 9S°C to produce a degummed vegetable oil; e, bleaching of the degummed vegetable oil to produce a bleached vegetable oil; and

f. deodorizing the bleached vegetable oil to produce a refined vegetable oil.

Although the inventors do not wish to be bound by theory, it is believed that by removing the total chlorine from the crude vegetable oil which is the precursor to the formation of 3~monochloropropane~i,2~dioi fatty acid esters (3-MCPD) prior to the degumming, bleaching and deodorization stages, would subsequently produce refined vegetable oil with reduced content of 3-MCPD esters.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig, i is a process flow diagram showing the steps involved according to the present invention.

FSg. 2 is a process fiow diagram showing the various vegetable oil product after going through each step of the process as claimed in the present invention.

Fig.3 is a diagram to show that the dechlorination step Is done via soaking, mixing or using size exclusion column according to the present invention. DETAILED DESCRIPTION OF THE INVENTION Referring to Fig. 1 and Fig. 2, the present invention relates to a process for producing refined vegetable oil, the process including the steps of:

a. heating a crude vegetable oil at temperatures between 55°C to 95°C to produce a heated crude vegetable oil;

b, providing between 0.5w/w to i.Qw/w of a dechlorination agent to the heated crude vegetable oii to produce a dechiorinated vegetable oil, wherein the dechlorination agent is selected from sodium m eta bisulfite, sodium bisulfite, sodium thiosulfate, sulfur dioxide, sodium ascorbate, hydrogen peroxide, sodium nitrite, sodium sulphite, calcium thiosulfate or any combination thereof for a dechlorination period of between I to 50 days;

c. filtering the dechiorinated vegetable oii to remove the dechlorination agent;

d, degumrning of the dechiorinated vegetable oil with organic acids at the temperature range between 85°C to 9S°C to produce a degummed vegetable oil; e, bleaching of the degummed vegetable oil to produce a bleached vegetable oil; and

f, deodorizing the bleached vegetable oil to produce a refined vegetable oil.

The term "oii" whenever used herein encompasses oils that, are liquid, semi-solid or solid at 20°C. The crude paim fruit oil employed in the present process usually contains solid fat. However, the present invention also encompasses the use of fractions of palm fruit oil that are completely liquid at ambient conditions and that are passed through the UP membrane without prior heating.

A suitable analytical method for determining 3-MCPD fatty esters content of oils is described in AOCS Official Method Cd 29a~13. Gtycidy! esters are converted to 3- monobromopropanediol (3-MBPD) monoesters in an acid solution containing a bromide salt. 3-MBPD esters, together with 2- and 3-MCPD fatty esters, are then converted into the free (rton-esteriffed) form in acid methanoJic solution. The fatty acid methyl esters generated during the reaction are extracted from the sample; 3- MCPD and 3-MBPD, are then derivatized with phenylboronic acid prior to GC-MS analysis. The total chlorine content of oils can be suitably determined by Mitsubishi NSX-2100 Hi Trace Elemental Analyzer in accordance to standard ASTM D4929. The trace elemental analyzer is a furnace system with a micro-cou!ornetric detector that was used for measuring and detecting total chlorine whether in organic or inorganic form.

The crude vegetable oil used in the present process typically contains total chlorine content of between i to 15 ppm. Examples of crude vegetable oils that may be refined by the present process include crude palm oil, crude palm oil fraction, palm oleirs, palm stearin or any combination thereof.

The process of the present invention comprises a dechlorination step for removing chlorine present in crude vegetable oils. Dechlorination agents are commonly used for removal of free chlorine in water. The dechlorination step before degumming process surprisingly is able to reduce total chlorine in crude vegetable oils. It is believed that the chlorine present in the crude vegetables oils attaches with the dechlorination agent by utilizing hydrogen bonds acceptor available in the dechlorination agent (for Sodium Metabilsu!fite it is 6 _f ) with moisture that acts as s catalyst. Although the lone pairs in the chloride ion are at the 3-ievei and would not normally be active enough to form hydrogen bonds, however, in this case they are made more attractive by the full negative charge on the chlorine. The chlorine will further be removed from the crude vegetable oil via filtration process.

Heating of crude oils and fats reduces the oil viscosity and this in turns improves the homogeneity rate of the vegetable oil with dechlorination agents. Preferably, 0«5w/w - iw/w dechlorination agents are used in this step. Upon testing, the inventors have found this range to be an optimum range for this process and using more than iw/w do not bring additional benefits and would also render this process to be not feasible for commercial applicability.

Referring to Fig. 3 _r the heated oil will undergo dechlorination process either by soaking, mixing or pass through into size exclusion column packed with dechlorination chemical. This process requires a dechlorination period of between 1 to 21 days. This said range is selected because no changes were observed after 21 days. Soaking, mixing or size exclusion coiumn methods are chosen as these are preferable and feasible methods to be performed at a commercial scale in the refinery.

The heated oii is then brought in contac with the dechlorination agents via soaking the heated vegetable with the dechlorinated agent, mixing the heated vegetable with the dechlorinated agent, passing through the heated vegetable oil at a flow rate of between 3mi/minute to I8ml/mtnute. through a size exclusion column filled with dechlorination agen or any combination thereof to produce a dechlorinated vegetable oil, Preferably, the heated oil is brought in contact with the dechlorination agents via soaking, as highest reduction in total chlorine content is observed using this method. The crude vegetable oil is heated to a temperature range of between 90°C - 95°C under vacuum prior to contacting it with dechlorination agents if the dechlorination to be conducted via mixing. Vacuum condition is required to prevent oil oxidation which will degrade the quality of the refined vegetable oil. Th crude vegetable oil is heated to a temperature range of between 55°C - 60°C prior to contacting it with dechlorination agents if the dechlorination to be conducted via soaking or size exclusion column. The heating temperature for the crude vegetable oii must be more than 50°C due to the melting temperature of the crude vegetable oil being more than S0°C. The dechlorinated vegetable oil is then filtered to remove the dechlorination agents before degumming process, to remove ail chlorine adsorbed by the dechionnation agents. If the dechlorination agents are not removed, then chlorine wilt be released back to the vegetable oil during the degumming process when acids used in the degumming process connects with the dechlorination agents. The degumming process is carried out to produce a degummed vegetable oil at a temperature range of 85 ^e C to 95°C with addition of 0,06% organic acids such as citric add and phosphoric acid (preferably with a concentration of 85%} and operated under vacuum: condition for 20 minutes. The degurnmed vegetable oi! is then bleached by contacting the degurnmed vegetable oil with a bleaching adsorbent selected from selected from bentonite day, paiygorskite day, montmoriiionite day, smectite day or any combination thereof to produce a bleached vegetable oil. The bleaching step is done in a temperature range of between 95°C to 120°C and operated unde vacuum condition for 30 minutes. 90°C is the temperature used in a standard bleaching process in a refinery. 95°C to 120°C is suitable for this process to reduce 3-MCPD content in the refined vegetable oil. The final step of the refining process involves deodortzabon in which odoriferous matters and free fatty acids are removed from the degurnmed and bleached vegetable oil to produce odourless and bland refined oils and fats. Preferably, the operating temperature is at the range of between 220°C to 240°C and at operating pressure range of between 2 mmHg to 4 mmHg for a time period of between SO minutes to 90 minutes. 24Q°C would be the maximum temperature to be used in this process as temperature higher than this will encourage the formation of 3-MCPD.

In a preferred embodiment, the dechlorinated vegetable oil contains between 0.5 ppm to 3 ppm total chlorine content, preferably 1 ppm more preferably 0.5 ppm, prior to the deodorization step.

Advantageously,, the present process produces a refined palm fruit oil having a 3- MCPD ester content between 0 ppm to 4,0 ppm, preferably 0 ppm to Ippm, more preferably 0,4 to 0,8 ppm.

The invention is further illustrated by the following non-limiting examples,

EXAMPLES

Example ΙΑϊ

Crude palm oii with the total chlorine content of 4,443 ppm was stored at 40°C for 7 days, and heated up at 55°C before degurnmed using phosphoric acid, and bleached using 2% natural clay at i20°C for 30 minutes under vacuum condition. Subsequently a deodorization treatment was carried out at 240°C under vacuum condition of 2 - 4 mmhig respectively and operated for 90 minutes respectively.

The content of 3-MCPD ester in refined paim oil was 2.44 ppm.

Example IB;

The same crude palm oii as used in Example 1A above was added with 1% of sodium metabisuifite and the oil was stored at 40°C for 7 days. Th oil was heated up at 55°G and filtered before the degumming process using phosphoric acid, and bleached using 2% natural clay at 12Q°C for 30 minutes under vacuum condition. Subsequently a deodorization treatment was carried out at 240°C under vacuum condition of 2 - 4 rrsmHg respectively and operated for 90 minutes respectively,

Total chlorine in dechiorinated palm oil was 0.724 ppm.

The content of 3-MCPD ester in refined palm oil was 0,51 ppm,

Example 1C:

The same crude paim oil as used in Example 1A was added with 1% of sodium metabisuifite and stored at 40°C for 21 days. The oil was heated up at 55°C and filtered before degummed using phosphoric add, and bleached using 2% natural day at 120°C for 30 minutes under vacuum condition. Subsequently a deodorization treatment was carried out at 24Q ^<5 C under vacuum condition of 2 - 4 mmHg respectively and operated for 90min respectively. Total chlorine in dechiorinated oil was 0.58 ppm.

The content of 3-HCPD ester in refined palm oil was 0.4 ppm.

Example 2A: Crude palm oil with a total chlorine content of 2.8 ppm was degummed using phosphoric acid, and bleached using 2% natural clay at i20 ^o C for 30 minutes under vacuum .condition. Subsequently a deodorization treatment was carried out at 240°C under vacuum condition of 2 - 4 mmHg respectively and operated for a 90 minutes respectively.

The content of 3-MCPD ester in refined palm oil was 1.91 ppm,

Example 28:

The. same crude palm oil used in Example 2A was added with 1% of sodium metabisuifite was added and the mixture was stirred at 95° ^' C for 30 minutes under vacuum condition.

Total chiorine in dechiorinated oil was 2.065ppm.

The content of 3-MCPD ester in refined palm oil was 1.12 ppm .

Example 2C:

The same crude palm oil used in Example 2A was added with 1% of sodium metabisuSfite and the mixture was stirred at 95°C for 30 minutes under vacuum condition. Total chlorine in dechiorinated oil was 2.05? ppm.

The content of 3-MCPD ester in refined palm oii was 1.03 ppm .

Example 3 A: Crude paim oil with 1.653 ppm total chiorine was degummed using phosphoric acid, and bleached using 2% natural clay at 120°C for 30 minutes under vacuum condition. Subsequently a deodorization treatment was carried out at 240°C under vacuum condition of 2 ~ 4 mmHg respectively and operated for 90 minutes respectively. The content of 3-MCPP ester in refined paim oil was 3 ,55 ppm . Example 3B: Size exclusion column was packed with iOOg sodium metabisulfite and 6000ο, of the same crude palm oil as per Example 3Ά above was passed through column with fiowrate 17mi/minutes and at column temperature of 55°C.

Totai chlorine in the ech!orinated oil was 1.072 ppm,

The content of 3-MCPD ester in refined palm oil was 1 ,36 ppm ,

Example 4Ai

Crude palm oil with a total chlorine content of 4.95 ppm was degummed using phosphoric acid, and bleached using 2% natural clay at 120°C for 30 minutes under vacuum condition. Subsequently a deodorization treatmen was carried out at 240°C under vacuum condition of 2 - 4 mmHg respectively and operated for 90 minutes respectively. The content of 3-MCPD ester in refined palm oil was 2.98 ppm. Example 4 t

The same crude paim oil used in Example 3A above was added with 1% of sodium bisulfite was added and the mixture was stirred at 95°C for 30 minutes under vacuum condition.

Total chlorine in dechlorinated oil was 2. 08 ppm .

The content of 3-MCPD ester in refined palm oil was 1 ,83 ppm.

Example 4C:

The same crude palm oil used in Example 3.A above was added with 1% of sodium thiosuifate was added and the msxture was stirred at 95°C for 30 minutes under vacuum condition . Total chlorine in dechlorinated oil was 1.77 ppm.

The content of 3-MCPD ester in refined palm oil was 1.4 ppm.

Summary Results:

Example Starting Process Conditions Total 3-MCPD

Material Chlorine Content

(CPO) Content

1A TC Stored at 40°C for 7 days (control) 2.44 ppm

J content

of 4.443 Heated to 5S°C

ppm

Degumming using phosphoric

acid

Bleaching with 2% natural clay

(120°C for 30 minutes)

IB TC Add with 1 % of sodium Dechlorina 0.51 ppm content metabisuifite ted palm of 4.443 oil: 0.724 ppm Stored at 40°C for 7 days ppm

Heated to 55°C

Degumming using phosphoric

acid