GB2141438A - Deodorization and stabilisation of palm oil and palm oil fractions - Google Patents

Abstract

Palm oil and palm oil fractions are deodorized and/or stabilized against oxidation by contacting with a sulphite ion source, preferably sodium bisulphite or metabisulphite. The oil or oil fraction may be contacted with an aqueous solution of sulphite ion, e.g. at 30 DEG C (for palm oil olein) or 60 DEG C (for palm stearin). A palm oil or palm oil olein having a carotene content of above 250 ppm, which has not been subjected to high temperature deodorisation, and has a stability against oxidation, as measured by the AOM test, of above 100 is obtained.

Description

SPECIFICATION Deodorization and stabilsation of palm oil and palm oil fractions The present invention relates to a process for the deodorizing and stabilizing against oxidation of palm oil ora palm oil fraction.

Vegetable oils develop rancidity chiefly through oxidation by air producing carbonyl compounds such as aidehydes and ketones as well as alcohols and acids. These are largely derived by the auto-oxidation of the unsaturated components ofthe oils.

In palm oil, compounds of a similartype give even the fresh oil a characteristic odourwhich is considered undesirable.

Processes are known forthe removal ofthe odour giving constituents of oils, such as high temperature vacuum steam distillation. Such a process is known as "steam deodorisation".

Palm oil however contains substantial concentrations of carotenes which are valuable as colouring materials and as precursors for vitamin A. The concentration of carotenes in palm oil varies substantially according to the exact source ofthe oil but is generally within the range of 250 ppm to 3000 ppm.

Carotenes are destroyed by the steam deodorisation process. The steam deodorisation process is also one requiring substantial amounts of energy.

The present invention now provides a process for deodorizing a palm oil ora palm oil fraction and/or stabilizing the oil against oxidation,which process comprises contacting the oil or oil fraction with a source of a sulphite ion.

Preferably, the source ofthesulphite ion is an alkali metal sulphite, bisulphite or metabisulphite, especially sodium bisulphite or sodium metabisulphite.

Usually,the oil will be treated with from 0.1 to 10% of sulphite ion (based on the weight of oil) but other amounts can be used. Preferably, the oil is treated with from 1% to 5% of sulphite ion, e.g. about 1.5% of sulphite ion.

The process may be carried simply by agitating the oil in contact with an aqeuous solution containing the sulphite ion, e.g. as bisulphite, or by direct addition of sulphite ion,eg. as metabisulphite. It is preferred to use a mildly acid sourceofsulphite ion such as bisulphite.

Preferably, the oil is washed with water after being treated with the sulphite.

It is conventional in the refining of palm oil to remove the free fatty acid content ofthe oil chemically by treating with a base, such as 5% w/v aqueous sodium hydroxide in admixture with isopropyl alcohol in the ratio of 4:1 or physically by high vacuum distillation. It is preferable that such removal takes place before the treatment with sulphite according to the present invention. The exact manner of free fatty acid removal is not of significance and any conventional method may be employed. It has been found that, if there fatty acid is not removed before the present treatment, the oxidative stability of the oil is not seriously impaired but the bleachabilityofthe oil suffers.

If desired, the freefatty acid can be removed by solvent extraction with alcohol or aqueous alcohol as disclosed in our co-pending Application No. 8317543, the conent of which is incorporated herein bythis reference.

It is also conventional to treat palm oil or palm oil fractions with an antioxidant. Examples of antiox idantswhich are conventionally used are butyl hydroxyanisole (BHA), propylgallate, butyl hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ).

The palm oil or palm oil fraction to be treated according to the present invention can with advantage be treated with a conventional antioxidant amount of such conventional antioxidants, e.g. 0.02%, before treatment according to the invention.

The process according to the invention may be carried out at any temperature found convenient.

Generally, it will be necessary to operateata temperature sufficiently highto produce adequate fluidity inthe oil but it is undesirable to work at an unnecessarily high temperature both on the grounds of unnecessary use of energy and on the ground that highertemperatures may cause deterioration of the carotenes, as is well known. Generally, the process according to the invention may be carried out at about 30"C except in the case of treatment of a palm stearin fraction.On account of the higher melting point of palm stearin, it is generally desirable to operate at about60 C. It is generally desirableto carryoutthe final washing and separation ofthe oil from aqueous phases at about 60"C. The process according to the invention is applicable to crude palm oil, to foots palm oil, to palm olein, and to palm stearin. However, the improvements in the oxidative stability of palm stearin obtained is less than for palm oil olein, whole palm oil orfoots palm oil.

The sulphite may be rinsed from the treated oil, but we have established that oil having a content of added sulphite exhibits enhanced stability.

It has beenfoundthat, in contrast to its effect on palm oil and its fractions, treatment by the process according to this invention is not effective in increasing the oxidative stability of vegetable oils generally although a decrease may be obtained in the level of primary and secondary oxidation products contained in such oils.

The invention also provides a palm oil or palm olein having a carotene content of above 250 ppm and a stability against oxidation as measured by the AOM testofabove 100.

The invention further provides a palm oil or palm olein which has not been subjected to a high temperature deodorisation procedure and has a stability against oxidation as measured by the AOM test of above 100.

The present invention will now be illustrated by the following Examples.

In the Examples, the following tests are applied and are referred to by their conventional abbreviations as indicated below: AOM = Active Oxygen Method (American Oil Chemist's Society Official Method Cd 12-57) - stan- dard measurement of oxidative stability in terms of the time (in hours) required to attain a predetermined peroxide value under specified conditions; PV = Peroxide Valuemilltequivalents of active oxygen per keg oil-a mixture of primary oxidation products; AV = Anisidine Value, 100 x E% cm at 350 nm-a measure ofthe amount of aldehydes (secondary oxidation products) in the oil; TV = Totox Value = (2 x PV) + AV;; SCOPA = Seed Crushers and Oil Producer's Asso ciation bleachability test- a standard test ofthe bleachability ofthe colour ofthe oil carried out using a Lovibond Tintometer (Type D) 13.4 cm (51/4") cell as follows: 1. Heat 100 gm of crude palm oilto 90'with agitation under nitrogen blanked. Add 0.5 ml of 20% w/w of reagent grade citric acid in water and maintain at 90"C for 10 minutes.

2. Add 2% of Tonsil Standard FF bleaching earth (2gm), raise temperature to 105and maintain under nitrogen blanketfor 15 minutes.

3. Filterthe hotoil earth mixture into a preheated 500 mlBuchnerflask,throughaWhatman No: 1 filter paper. Filter aid should not be necessary.

4. Transfer 90 + 1 gm of the filtrate to a 250 ml round bottomed flask, add a fewanti-bumping granules, and draw a vacuum of 1-2 mm HG. Heat mixture, without agitation, to 260"C + 1 C within 10 mins and maintain for 20 minutes.

5. Cool undervacuum as rapidly as is possible and safe to do.

6. When cooled to 60"C release the vacuum and measurethe colourin a 5-" Lovibond cell, using the BS 684/FOSFA method.

7. Thetest must be completed within 2hrs. of starting to degum.

Neutralisation: where in the following Examples an oil tested is said to have been neutralised, the procedure employed was as follows: The oil, orthe oil fraction, concerned was agitated with an equal volume of a solution prepared by mixing four parts byvolùme of a 5% w/v aqueous sodium hydroxide and 1 partpervolumeofisopropylalcohol (IPA) at 29"C, (except in the case of palm stearin where the process was carried out at 60"C) and under a blanket of nitrogen. The inert atmosphere is provided to prevent aerial oxidation atthisstage. Generally, in the processing of palm oil and palm oil fractions, unnecessary exposure to oxygen is to be avoided.The oil was then separated fromthebasesolution by centrufugation and washed with an equal volume of water and once again separated by cent(ifugation. The washing stepwas repeated twice.

Fractionation: Tests are carried out in the Examples below upon both crude palm oil and fractions obtained therefrom. In each case, olein and stearin fractions were obtained by mixingthe palm oil with a water: isopropanol mixture (44:56 v/v) in a ratio of2:1 in a centrifuge tube. This was centrifuged for 30 minutes at 29 Cto provde olein and stearin fractions.

Example 1 The oil or oil fraction indicated in Table 1 below was subjected to neutralisation and was then mixed and homogenised with an equal volume of a 10% weight/ volume solution of sodium bisulphite for 5 minutes at 30 C under a blanket of nitrogen and was then separated by centrifugation. The oil was then washed twice with distilled water, the final washing being carried out at 60"C. For palm stearin, the whole process was carried out at 60"C. The results ofthis procedure are shown in Table 1 below. The control in each case was the unneutralised palm oil or palm oil fraction indicated.

TABLE 1

Bleachability AOM Fatty acid Oil Sample PV AV FFA Totox (hours) Methyl Ester% % Sat. Unsat. P Palm Oil Control 3.2-7 2.53 2.74 9.07 2.0R 18.0 68 49.5 50.4 Sulphite O. 1.83 0.12 1.83 1.OR l.0Y 282 50.4 49.7 Treated Palm Olein Control 7.4 1.36 2.97 16.22 2.6R 23.0Y 21 47.1 50.7 Sulphite 0.0 1.43 0.08 1.43 1.4R 13.OY 222 46,8 53.4 Treated Foots Control 10.8 14.57 4.07 36.31 5.CR 40.0Y 8 14.9 50.1 Palm Oil Sulphite 0.0 7.94 0.13 7.94 1.9R 20.OY 217 50.4 49.5 Treated Palm Control 16.8( 8.09 3.29 41.69 5.3R 41.0Y 52 55.0 45.3 Stearin Sulphite 0.0( 4.92 0.12 4.92 2.OR 25.0Y 92 55.3 44.9 Treated It can be seen that the process according to the invention has provided a very significant increase in case, that in respectoffoots palm oil being particularly dramatic. The improvement in the stability ofthe palm stearin fraction was in comparison much less but was nonetheless significant.

EXAMPLE2 The oil or oil fraction indicated in Table 2 below was subjected to r.eutralisation, 200 ppm ofthe antioxidant BHAwasthen added to the oil and the oil was then subjected to a treatment in accordance with the invention as described in Example 1. As an additional control, a mixture ofthe untreated oil with 200 ppm of the antioxidant BHAwas prepared. The results ofthe treatment according to the invention can be seen from Table 2 below. In the Table, the "Control" is oil withouttreatment; the "Control 200 ppm BHA" is oil withouttreatmentwith 200 ppm BHAadded; the "Neutralised + 200 ppm BHA" is oil with 200 ppm BHAadded after neutralisation and washing; andthe "Sulphite Treated" is oil with 200 ppm BHAadded treated according to the process ofthe invention as described in Example 1.

TABLE 2

Pro Properties AOM Fatty acid % Oil Sample PV AV % Totox Bleachability (hours) Methyl Ester FFA Sat. Unsat.

Palm Oil Control 2.84 4.00 2.99 9.68 1.78 16.0Y 35 51.5 48.5 Control + 200 pmr 2.84 4.00 2.99 9.68 1.78 16.0Y 34 50.7 49.2 BHA Neutralised + 20 3.4 2.64 0.08 9.48 1.lR ll.OY 37 51.3 48.6 ppm BHA Sulphite Treated 0.0 2.25 0.15 2.25 0.8R 13.0? 404 50.2 49.8 Palm Olein Control 6.5 2.12 2.91 15.26 2.5R 32.0Y 21 47.7 52.3 Control + 200 pmm 6.3 2.18 2.91 14.90 2.5R 24.0Y 26 47.6 52.6 ERA Neutralised + 20 5.91 2.12 0.09 13.94 2.1R 20.0Y 25 46.9 53.0 BHA Sul hite Treated 0.00 0.24 0.08 0.24 1.4R 19.0? 83 47.3 52.7 Foots Control 10.7 14.99 4.16 36.45 4.7R 40.0Y 9 49.9 50.1 Palm Oil Control + 200 p 10.8 15.21 4.10 36.99 4.68 40.0Y 11 51.0 49.1 BHA Neutralised + 20 7.6 10.73 0.17 35.97 2.1R 20.0Y 50 51.9 48.1 ppm BRA Sus hit Treated 0.0 8.19 0.17 8.19 1.7R 19.0Y 114 50.4 49.5 It can be seen that the provision of the anti-oxidant prior to the treatment according to the invention has had a remarkably beneficial effect in the case of palm oil itself but appears to have hada deleterious effect in respect of palm olein and foots palm oil.

Example 3 This Example illustrates the effect of omitting the neutralisation step prior to carrying outthe process according to the invention. Asample of crude palm oil was treated in accordance with the invention as described in Example 1 but without being neutralised and subjecttothe modification that in a first run a 1% solution of sodium bisulphite was employed and in a second run a 10% solution of sodium bisulphite was employed. As a control, measurements were carried out on a sample ofthe crude palm oil without neutralisation and without treatment according to the invention. The results are indicated in Table 3 below.

TABLE 3

Sample PV AV FFA Totox Iron Copper Phosphorous Tocopherol ppm % ppm ppm ppm Control 7.5 2.9( 3.55 17.96 6.4 2.1- 8.3 607 1% NaHSO3 0.0! 3.7( 3.4 3.88 3.1 0.9 0.0 512 10% NaBSO3 0.0t 2.9 3.5 2.9t 2.6 1.2 0.0 493 Fatty Acid % Triglyceride Sample Bleachability AOM Methyl Ester (hours) Sat. Unsat. C46 C48 C50 C52 C54 Control 6.2R 40.0Y 56 49.4 50.6 0.23 6.1 36.4 40.82 16.39 1% NaHSO3 5.6R 50.0Y 88 49.4 59.6 0.1 5.4 37.6 42.4' 14.26 10% NaBSO3 6.2R 40.0Y 425 48.3 51.7 0.16 3.5t3 36.7 45.2: 14.30 ltcan be seen thattreatmentwith a 10% weight/ volume sodium bisulphite solution increased the stability of the palm oil against oxidation to a degree ofthe same order of magnitude as in Example 2.

However, whereas in the case pf the neutralised oils treated in Example 2 the bleachability ofthe oil was very substantially improved, in the absence of neutralisation there was no corresponding increase in bleachability upon treatment according to the invention. Where it is not desired to obtain a bleached oil as a final product however this may not be a significant disadvantage.

Example 4 The effect of treatment according to the invention on the constitution of palm oil and its fractions is illustrated in Table 4 below. Each sample was treated according to the procedure of Example 1. It can be seen that there is a reduction particularly marked for foots palm oil, in the content of iron and copper, which are known to act as oxidation catalysts.

TABLE 4

Iron Copper Tocopherol Phosphorus Triglycerides oil Sample ppm ppm ppm ppm C46 C48 C50 C52 C54 Palm Oil Control 5.9 1.7 745 10.4 - 4.6 36.7 40.2 16.7 Sulphite 4.8 1.6 628 0.8 - 4.8 38,7 41.0 14.0 Treated Palm Olein Control 7.3 1.6 551 4.9 - 1.5 38.1 44.2 14.4 Sulphite 5.1 1.7 473 1.7 - 1.7 39.9 43.5 13.0 Treated Palm Control 6.3 1.0 125 6.6 0.6 15.8 39.4 31.2 10.5 Stearin Sulphite 4.4 1.1 45 0.8 0.5 16.3 23.7 32.0 10,6 Treated Foots Control 112.3 5.9 - 28.7 0.2 5.5 36.6 19^.7 14i.0 Palm Oil Sulphite 4.6 1.4 - 0.8 0.1 5.8 37.4 23.8 13.1 Treated EXAMPLES Sodium metabisulphite was added to a sample of completely liquid crude palm oil to produce the bisulphite in concentrations shown in Table 5A below and the AOM value was determined.The substantial effect of providing a concentration of 400 ppm or more can be seen.

TABLE 5A

ppm 11503 added AOM (hours) 62 50 73 100 75 200 93 400 490 800 555 The above procedure was repeated for palm stearing, soyabean oil, cottonseed oil, sunflower oil and groundnut oil and the results are setfurther in Table 5B below.

TABLE 5B Sample ppm HSO; added AOM (hours) Palm Stearin - 62 - "- 200 70 - '. - 400 75 Soyabean oil - 6 - " - 400 6 Cottonseed Oil - 5 - - 400 5 Sunflower Oil - 8 - " - 400 8 Groundnut Oil - 14 - ', - 400 15 It can be seen from Tables 5A and 5B that, whereas sodium imetabisulphite improved the AOM stability of crude palm oil and palm stearin, it had no effect on the stability of the other vegetable oils.

Comparative Example Soyabean oil, cottonseed oil, groundnut oil and sunflower oil were each subjected to a treatment with bisulphite solution as described in Example 1 and their stability to oxidation as well as other parameters werethen measured. Table 6 below shows the results obtained.

TABLE 6

Oils Sample PV AV FFA Totox AOM 1. Soyabean Control 22.55 6.42 0.10 51.52 7 Sulphite Treated 0.66 11.09 0.10 12.41 8 2. Cottonseed Control 22.64 7.33 0.12 52.61 18 Sulphite Treated 0.86 10.52 (1.15 12.24 7 3. Groundnut Control 5.56 2.62 0.47 13.74 17 Sulphite Treated 1.14 2.72 0.60 5.00 18 4. Sunflower Control 24.59 13.16 0.15 62.34 8 Sulphite Treated 1.83 15.67 0.15 19.33 7 It can be seen that whilst there was a substantial decrease in the level of primary and secondary oxidation products as measured as PV and AVvalues there was no corresponding increase in stabilityto oxidation obtained.

EXAMPLE 6 Palm olein was neutralised and then homogenized (5 mins) under a blanket of nitrogen with an equal volume of 2% w/v sodium bisuiphite solution at 29"C.

The mixture was centrifuged (5 mins), 2000 rpm) and the olein separated from the aqueous layer. This olein was then again homogenized (5 mins) under a blanket of nitrogen with an equal volume of distilled water at 29"C. The mixture was centrifuged (5 mins, 2000 rpm) and the oleinseparated from the aqueous layer. The washing was repeated twice with the last centrifuging time increased to 15 mins. The olein was separated and the qualities analysed.

The procedure abovewas repeated except that 0.02% w/vt-butylated hydroquinone (t-BHQ) or butylated hydroxyanisole (BHA) was added before treatment with the sodium bisulphite solution and the concentration of the second solution was 5% w/v.

The results are shown in Table 7.

TABLE 7

Antioxidant Palm Olein PV AV FFA Total Control 0.28 1.91 2.65 2.47 NONE Sulphite treated 0.37 0.99 0.12 3.73 Control 2.26 1.32 2.82 5.40 BRA Sulphite treated 0.00 1.50 0.13 0.50 Control 4.54 1.52 2.94 10.60 t-BBQ Sulphite treated 0.00 0.80 0.17 0.80 EXAMPLE 7 The procedure of Example 6wassubstantially repeated except that 0.02% w/v butylated hydroxyanisole was added before the treatment with sodium bisulphite and different concentrations of sodium bisulphite (1%, 2%, 5% and 10% ) were used.

The palm olein starting material was obtained by warming palm oil from a fractionation of crude palm oil to 90"C in a water bath and drawing airthrough it using an aspirator.

After 5 hours a portion ofthe palm olein was taken and kept under nitrogen for use in the sodium bisulphitetreatments. The peroxide value of this portion was 0.65. Two further portions were taken after8 hours and 10 hours ofaeration and had peroxide value of 1.2 and 2.2 respectively. Again, these samples were stored under nitrogen until requiredforsodium bisulphite treatment.

It was found that the peroxide value of the treated olein decreased with increase in sodium bisulphite concentration andthatthe anisidinevaluesof all treated olein samples were reduced compared with the untreated olein. The results are set forth in Tables 8A, 8B and 8C below.

TABLE 8A

Conc.NaHSO3(w/v) Palm Olein PV AV FFA Totox 1% Control 0.65 1.86 2.87 3.16 Sulphite treated 0.28 0.86 0.12 1.42 2% Control 0.65 1.86 2.87 3.16 Sulphite treated 0.09 0.37 OI1 0.55 5% Control 0.65 1.86 2.76 3.16 Sulphite treated 0.00 1.22 0.09 1.22 10% Control 0.65 1.86 2.76 3.16 Sulphite treated 0.00 0.99 0.09 0.99 TABLE 8B

Conc.NaHSO3 (w/v) Palm Olein PV AV FFA Totox 1% Control 1.04 1.52 2.74 3.60 Sulphite treated 0.43 1.17 0.11 2.03 2% Control 1.28 1.10 2.76 3.66 Sulphite treated 0.19 0.45 0.06 0.83 5% Control 1.28 1.37 2.87 3.93 Sulphite treated 0.00 1.00 0.24 1.00 10% Control 1.22 1.49 2.75 3.93 Sulphite treated 0.00 0.50 0.25 0.50 TABLE 8C

Conc.NaHSO3(w/v} Palm Olein PV AV FFA Totox 1% Control 2.12 1.32 2.88 5.56 Sulphite treated 0.28 1.43 0 0.21 1.99 2% Control 2.12 1.32 2.88 5.56 Sulphite treated 1 0.09 0.57 0.13 0.75 5% Control 2.26 1.32 2.82 5.84 Sulphite treated 0.00 0.50 0.13 0.50 EXAMPLE 8 The procedure of Example 6 was substantially repeated except that 0.02 w/v butylated hydroxyanisole was added before sodium bisulphite treatment and 5% w/v aqueous sodium bisulphite was used.

The sodium bisulphite treatment and subsequent washing was conducted at various temperatures, namely40 C, 50 C 60 C and 70 C. It was found that an increase in temperature raised the peroxide and anisidinevalues of the treated olein. The results are set forth in Table 9 below:: TABLE 9

Temperature | Palm Olein | PV AV FFA Totox 30 Control 2.26 1.32 2.82 5.84 Sulphite treated 0.00 0.50 0.13 0.50 40 Control 2.26 2.00 2.75 6.92 Sulphite treated 0.00 3.57 0.15 3.51 50 Control 2.46 2.00 2.75 6.92 Sulphite treated 0.19 1.48 0.17 1.86 60 Control 2.46 1.38 2.84 6. 30 Sulphite treated 0.76 2.24 0.12 2.80 70 Control 2.26 0.79 2. 81 5. 5.71 Sulphite treated 0.76 2.24 0.08 3.76 EXAMPLE9 Crude palm oil was neutralised and the neutralised oil wasthen washed six times with equal volume of distilled water. The last washing was carried out at 60 C. No antioxidantwas used. The various properties of the treated oil were anlysed.

The above procedure was carried outwith another sample of crude palm oil but was washed only three timeswith equal volume of distilled water.

There was improvement in the bleachability ofthe oil although the totox value showed only slight improvement. The results are setforth in Table 10 below: TABLE 10

Sample FV AV FFA Totox Iron Copper Phosphorous Tocopherol Bleachability (Lovibond % ppm ppm ppm ppm 5" cell) Red Yellow Control 16.25 4.96 3.96 37.19 10.3 1.18 9.0 395.4 10.0 70 NW * 10.23 3.56 0.08 24.00 2.0 0.73 0.0 321.0 3.6 10 MW * 10.96 3.66 0.10 25.58 2.0 0.87 0.0 317.4 3.3 30 Fatty Acid % Sample AOM Methyl Ester Triglyceride % (hours) Sat. Unsat. C46 C48 C50 C52 C54 Control 14 50.0 49.9 0.21 6.16 36.40 40.84 16.39 NW * 34 50.2 49.7 0.29 6.39 36.80 41.44 15.08 NW * 33 50.2 149.8 0-.28 6.49 37.60 42.04 13.59 * NW3 - Palm Oil sample neutralised with 5% sodium solution/IPA mixture and washed 3 times with distilled water * MW6 - Palm Oil sample neutralised with 5% sodium solution/IPA mixtures and washed 6 times with distilled water The present invention as exemplified has made it possible to obtain a palm oil or palm oil fraction containing high, e.g. natural, levels of carotene and yet stabilised against oxidation whereas in the past, the steps taken to refine the oil have led to the destruction ofthe valuable carotene components.

The invention had provided palm oil and palm oil fractions which have not been subjected to a high temperature deodorisation process and yet which possess stability against oxidation.

Claims (20)

1. A process for deodorizing and/orstabilising a palm oil or a palm oil fraction against oxidation which process comprises contact the oil or fraction with a source of a sulphite ion.

2. A process as claimed in Claim 1, wherein the source of sulphite ion is an alkali metal sulphite or, bisulphite or metabisulphite.

3. A process as claimed in Claim 2, wherein the source of sulphite ion is sodium bisulphite or sodium metabisulphite.

4. A process as claimed in any one of the preceding claims, wherein the oil orfraction is treated with from 0.1% to 10% ofsulphite ion (based upon the weight of oil).

5. A process as claimed in Claim 4, wherein the oil or fraction is treated with from 1% to 5% ofsul phite ion.

6. A process as claimed in any one of the preceding claims,whereinthe oil or fraction is agitated with an aqueous solution containing sulphite ion.

7. A process as claimed in Claim 6, wherein the aqeous solution is a mildly acid aqueous solution.

8. A process as claimed in any one of the preceding Claims, wherein the oil or fraction is washed with water after being treated with the sulphite ion source.

9. A process as claimed in any one of the preceding Claims, wherein the free fatty acid content ofthe oil or fraction is neutralised by treatment with base prior to treatment with the suiphite ion source.

10. A process as.claimed in any one of the preceding Claims, wherein an antioxidant amount of butylhydroxyanisole, propylgallate, butyihydroxyto- lueneortertiarybutylhydroquinone is addedto the oil prior to treatment with the suiphite ion source.

11. A process as claimed in any one of the preceding Claims, wherein the palm oil or palm oil fractioniswhole palm oil.

12. A process as claimed in any one of Claims 1 to 10 wherein the palm oil or palm oil fraction is foots palm oit

13. A process as claimed in any one of Claims 1 to 10 wherein the palm oil or palm oil fraction is palm oil olein.

14. A process as claimed in any one of Claims 11to 13,whereinthetreatmentwith the sulphite ion source is carried out at about 30"C.

15. A process as claimed in any one of the preceding Claims, wherein the palm oil or palm oil fraction is palm stearin.

16. A process as claimed in Claim 15, wherein the treatment with the suiphite ion source is carried out at about 60"C.

17. Aprocessforstabilising a palm oil or fraction thereof against oxidation by treatment with a sulphite ion source, substantially as hereinbefore described in any one of Examples 1 to 3.

18. Apalmoil or palm oilfraction deodorized an/or stabilised by a process as claimed in any one of the preceding Claims or a palm oil fraction obtained therefrom.

19. A palm oil or palm oil olein having a carotene content of above 250 ppm and a stability against oxidation as measured by the AOM test of above 100.

20. A palm oil or palm oil oleinwhich has not been subjected to a high temperature deodorisation procedure and has a stability against oxidation as measured by the AOM test of above 100.