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374 P. T. Gee Eur. J. Lipid Sci. Technol. 109 (2007) 373379

bleached and deodorized (RBD) palm oil. Although palm

oil can be processed into neutralized, bleached and deo-

dorized palm oil, the quantity of chemically refined palm

oil is very small as compared to the physically refined

RBD palm oil.

At the palm oil refinery, CPO is treated with ortho-phos-phoric acid for gum-conditioning, with bleaching earth for

bleaching, and then filtered to remove the gums and

adsorbed impurities. The bleached oil is then deacidified

and deodorized at 250265 7C under vacuum (,5 mmHg)

with steam stripping. Free fatty acids, odoriferous and

other volatile components are distilled and removed as

palm fatty acid distillate (PFAD), whereas the oil after

deacidification and deodorization is the RBD palm oil.

The semi-solid palm oil can be fractionated into palm

olein (the liquid fraction) and palm stearin (the solid frac-

tion). Detergent fractionation is used for fractionation of

CPO, whereas dry fractionation is normally used for frac-

tionation of RBD palm oil. Solvent fractionation is only

used for fractionation of high-value-added products such

as good-quality palm mid fraction. Multiple fractionations

can be carried out in order to achieve products with the

desired characteristics. Fractionation involves crystal-

lization at lower temperatures, followed by a filtration step

to separate the liquid and solid fractions.

3 Composition and characteristics of CPO

Just like other oils and fats, the main component of palmoil is triacyglycerols. All the unsaturated fatty acids in

palm oil triacylglycerols are having cis-configuration.

Commercial palm oil is also free from genetic modification

(GM), therefore all natural palm oil products should be

considered as having the same status of identity-pre-

served products. Tab. 1 summarizes the triacylglycerol

composition in palm oil [2]. 1-Palmitoyl-2,3-dioleoyl-sn-

glycerol and 1,3-dipalmitoyl-2-oleoyl-sn-glycerol are the

main triacylglycerols in palm oil; each constitutes about

one fifth of the total triacylglycerol content. The semi-solid

nature of CPO at room temperature (about 30 7C) isdue to

the presence of a wide spectrum of triacylglycerols,

comprising saturated triacylglycerols and triacylglycerols

with one, two, three, four or more double bonds.

The triacylglycerol composition reveals that the sn-2

position of palm oil triacylglycerols is mainly esterified

with unsaturated fatty acids (.58.25% oleic acid and

.18.41% linoleic acid). Dietary fat is hydrolyzed into fatty

acids and 2-monoacyl-sn-glycerols during digestion. Re-

esterification of 2-monoacyl-sn-glycerols with otheravailable dietary fatty acids into triacylglycerols shall

constitute as body fat. While fatty acids at the sn-1 and

sn-3 positions are hydrolyzed and may or may not be re-

esterified, the sn-2 position of dietary fat will remain intact

when converted into body fat.

The low polyunsaturated fatty acid content and high

levels of antioxidants in palm oil provide good oxidative

stability whereas the preferential enrichment of oleic and

linoleic acids in the sn-2 position provides better

bioavailabilty of oleic acid as monounsaturated fatty acid

and linoleic acid as essential fatty acid, as compared tooils and fats of similar composition but with randomized

fatty acid distribution.

Tab. 1. Triacylglycerol composition of palm oil [2].

Saturated 1 double bond 2 double bonds 3 double bonds 4 double bonds

[%] [%] [%] [%] [%]

MPP 0.29 MOP 0.83 MLP 0.26 MLO 0.14 PLL 1.08PMP 0.22 MPO 0.15 MOO 0.43 PLO 6.59 OLO 1.71PPP 6.91 POP 20.02 PLP 6.36 POL 3.39 OOL 1.76

PPS 1.21 POS 3.50 PLS 1.11 SLO 0.60 OLL 0.56PSP 0.12 PMO 0.22 PPL 1.17 SOL 0.30 LOL 0.14

PPO 7.16 SPL 0.10 OSL 0.11PSO 0.68 POO 20.54 OOO 5.38SOS 0.15 SOO 1.81 OPL 0.61SPO 0.63 OPO 1.86

OSO 0.18

Others 0.16 0.34 0.19 0.15 0.22

Total 9.57 33.68 34.01 17.27 5.47

M, myristic acid; P, palmitic acid; S, stearic acid; O, oleic acid; L, linoleic acid.

2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ejlst.com

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Eur. J. Lipid Sci. Technol. 109 (2007) 373379 Analytical characteristics of crude and refined palm oil 375

Tab. 2. Fatty acid composition of palm oil, palm olein and palm stearin [3].

Fatty acid Palm oil [%] Palm olein [%] Palm stearin [%]

Lauric, 12:0 0.100.40 (0.24) 0.200.40 (0.27) 0.100.30 (0.18)Myristic, 14:0 1.001.40 (1.11) 0.901.20 (1.09) 1.101.70 (1.27)

Palmitic, 16:0 40.9047.50 (44.14) 36.8043.20 (40.93) 49.8068.10 (56.79)Stearic, 18:0 3.804.80 (4.44) 3.704.80 (4.18) 3.905.60 (4.93)Oleic, 18:1 36.4041.20 (39.04) 39.8044.60 (41.51) 20.4034.40 (29.00)Linoleic, 18:2 9.2011.60 (10.57) 10.4012.90 (11.64) 5.008.90 (7.23)Linolenic, 18:3 0.050.60 (0.37) 0.100.60 (0.40) 0.000.50 (0.09)Arachidoic, 20:0 0.200.70 (0.38) 0.300.50 (0.37) 0.000.50 (0.24)

Values in parentheses are the mean values.

Oils and fats are often characterized by their fatty acid

composition. Oils and fats are transesterified into fatty

acid methyl esters (FAME) and FAME can be determined

by gas-liquid chromatography. Tab. 2 summarizes thefatty acid composition of palm oil and its fractions. The

fatty acid composition is less informative than the tri-

acylglycerol composition, but the gas-liquid chromato-

gram is easier to interpret due to lesser components. The

main fatty acids are palmitic acid (44.1%), oleic acid

(39.0%) and linoleic acid (10.6%). By using a highly polar

column (not shown in the Tab. 2), small quantities (,1%)

of palmitoleic acid (cis-9-hexadecenoic acid) and asce-

leptic acid (cis-11-octadecenoic acid, also called cis-

vaccinic acid) can be detected besides oleic acid (cis-9-

octadecenoic acid).

CPO also contains free fatty acids (,5%), mono-acylglycerols (0.210.34%) and diacylglycerols (5.3

7.7%) [4]. Tab. 3 summarizes the effects of fractionation

and refining on the monoacylglycerols and diacylglycer-

ols. While monoacylglycerols are reduced after refining,

Tab. 3. Effect of fractionation and refining on mono-acylglycerols and diacylglycerols [4].

Monoacyl-

glycerols

[%]

Diacyl-

glycerols

[%]

Crude palm oil 0.26 6.6

Bleached and degummed palm oil 0.17 6.7

RBD palm oil 0.08 6.9

Crude palm olein 0.24 7.3

Bleached and degummed palm olein 0.16 7.2

RBD palm olein 0.07 7.4

Crude palm stearin 0.41 4.2

Bleached and degummed palm stearin 0.27 4.3

RBD palm stearin 0.05 4.2

RBD, refined, bleached and deodorized.

diacylglycerols are not affected by the refining processes.

These components are hydrolytic metabolites and also

biosynthetic intermediates of triacylglycerols. While 1,3-

diacyl-sn-glycerols are the main diacylglycerols in CPOasthey are thermodynamically more stable than 1,2-diacyl-

sn-glycerols, the chiral 1,2-diacyl-sn-glycerols are the

indigenous diacylglycerols in the palm fruits [5]. Dia-

cylglycerols are considered undesirable in palm oil, as

they affect crystallization and clarity of palm olein upon

storage [6]. Synthetic diacylglycerol cooking oil, obtained

by interesterification of rapeseed or soybean oil with

glycerol, is used as anti-obesity functional food in Japan

and the USA.

4 Minor components

CPO is the richest natural source of carotenoids and

tocotrienols. Both carotenoids and tocotrienols are

potent fat-soluble antioxidants. It is interesting to note

that the commercial values of carotenoids and toco-

trienols in CPO exceed that of the CPO they are derived

from. Other minor components have lower commercial

values. Tab. 4 summarizes the minor components of

CPO.

The carotenoids (500700 ppm) are responsible for the

characteristic orange-red color of CPO. Tab. 5 sum-

marizes the carotenoids present in CPO. The main car-

otenes present in CPO are b-carotene (56%) and a-car-

otene (35%). Both b-carotene and a-carotene are provi-

tamin A. All carotenoids are destroyed during the normal

refining processes. Processes are available to refine red

palm oil without destroying the carotenoids. There are at

least three companies in Malaysia producing refined red

palm oil.

Tocotrienols are the most valuable component in CPO.

Tab. 6 summarizes the vitamin E composition of CPO.

a-Tocomonoenol, with a double bond at carbon-11 of the


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Tab. 4. Minor components of crude palm oil.

Component Total in CPO [mg/kg]

Carotenoids [7] 500700Squalene [8] 200500

Non-terpenoid hydrocarbons [9] 3050a-Tocopherol 1 tocotrienols [7] 6001000Sterols [10] 362627Triterpenic alcohols [11, 12] 4080Methylsterol [12] 4080Dolichols1 polyprenols [13] 81Ubiquinones [14] 1080Phospholipids [15] 5130Glycolipids [16] 10333780

Tab. 5. Carotenoid composition of CPO [17].

Carotene Composition [%]

Phytoene 1.27Phytofluene 0.06cis-b-Carotene 0.68b-Carotene 56.02a-Carotene 35.16cis-a-Carotene 2.49z-Carotene 0.69g-Carotene 0.33d-Carotene 0.83Neurosporene 0.29b-Zeacarotene 0.23Lycopene 1.30

Tab. 6. Vitamin E composition of CPO.

Vitamin E Composition [%]

[18] [19] [20] [21] Mean

a-Tocopherol 22.4 28.2 31.0 27.1 27.2g-Tocopherol Trace a-Tocotrienol 21.0 19.5 14.8 28.6 21.0b-Tocotrienol 2.9 4.0 2.2 1.4 2.6g-Tocotrienol 41.5 39.0 41.4 28.7 37.7d-Tocotrienol 12.1 9.4 10.7 14.2 11.6

Mean of the values from the four references. Data arenormalized for comparison.

hydrocarbon side chain, was first isolated and structurally

elucidated by mass spectroscopy and proton nuclear

magnetic resonance spectroscopy [22]. a-Tocomonoenol

is normally notreported and its significance is unknown. A

literature search revealed that there were two reports [22,

23] on a-tocomonoenol in palm oil, and the a-tocomo-

noenol levels were 12.8 and 40 mg/kg, respectively. The

tocopherol and tocotrienol profile in palm oil is distinctly

different from that of all other oils and fats. It should be

noted that the natural sources for tocotrienols are scarce.

Recent reviews revealed that tocotrienols are potentially

better chemo-prevention and chemotherapy agents fordegenerative diseases [24, 25] than a-tocopherol. For the

past half a century, misconceptions and lack of under-

standing have misled the clinical scientists to conduct

research on a-tocopherol only. Clinical outcomes from

a-tocopherol human intervention trials were very dis-

appointing, ineffective, and some even with negative cor-

relations.

The fate of the tocotrienols during refining is different from

that of the carotenoids. A small quantity of the toco-

trienols is adsorbed by the bleaching earth. High-perfor-

mance liquid chromatography indicates that the double

bonds along the farnesyl side chains of some of the

tocotrienols in PFAD are partially degraded during the

steam distillation. Other degraded products derived from

tocotrienols have been reported in PFAD [9]. The deaci-

dification and deodorization conditions (temperature and

vacuum) determine the quantity and quality of toco-

trienols that are distilled into PFAD.

The volatile minor components such as non-terpenoid

hydrocarbons, squalene and sterols are also distilled as

PFAD, together with vitamin E and degraded products

from carotenoids. The polar components such as phos-

pholipids and glycolipids are adsorbed by the bleachingearth and subsequently removed by filtration.

5 Palm oil fractions

The fatty acid compositions of a single fractionated palm

olein and palm stearin are given in Tab. 2, together with

that of palm oil. During fractionation, unsaturated fatty

acids are preferentially distributed in the palm olein

whereas saturated fatty acids are preferentially distribut-

ed in the palm stearin. Diacylglycerols, squalene, car-

otenoids, tocopherol and tocotrienols are also pre-

ferentially distributed in the palm olein. On the other hand,

monoacylglycerols, sterols and phospholipids are pre-

ferentially distributed in the palm stearin.

Tab. 7 summarizes the chemical and physical character-

istics of palm oil and its fractions. The iodine value is a

measure of unsaturation in oils and fats. Theoretically, it

can be calculated from the fatty acid composition, but in

practice, it is usually determined by titration using the Wijs

method. The ranges for both the fatty acid composition

and the iodine value of palm stearin are very wide. These


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Tab. 7. Characteristics of RBD palm oil and its fractions [3, 26].

Parameter Palm oil Palm olein Palm stearin

Iodine value 50.0954.91 (52.07) 55.5761.87 (56.75) 27.8445.13 (37.74)

Slip melting point [7C] 33.0039.00 (36.72) 19.2023.60 (21.45) 46.6053.80 (51.44)

Refractive index

#

1.45441.4550 (1.4548) 1.45891.4592 (1.4589) 1.44821.4501 (1.4493)Apparent density [g/mL] 0.88960.8910 (0.8899) 0.89690.8977 (0.8972) 0.88130.8844 (0.8822)

Solid fat content [%] at

10 7C 46.160.8 (53.7) 23.945.5 (38.3) 49.584.1 (76.0)

15 7C 33.450.8 (39.1) 10.725.9 (19.9) 37.279.0 (68.9)

20 7C 21.631.3 (26.1) 0.09.0 (5.7) 25.271.2 (60.2)

25 7C 12.120.7 (16.3) 0.04.3 (2.1) 15.863.5 (50.6)

30 7C 6.114.3 (10.5) 11.255.0 (40.4)

35 7C 3.511.7 (7.9) 7.246.6 (34.3)

40 7C 0.08.3 (4.6) 6.138.0 (28.1)

45 7C 1.032.2 (22.4)

50 7C 0.021.3 (12.5)

55 7C 0.09.1 (0.6)

#

Refractive index and apparent density for palm oil, palm olein and palm stearin were measured at50, 40 and 60 7C respectively. Values in parentheses are the mean values.

wide ranges are due to the methods and conditions used

in the fractionation. Detergent fractionation produces very

hard stearin (with low iodine values) whereas dry frac-

tionation produces intermediate and soft palm stearin,

depending on the rate of crystallization.

By further fractionation of palm olein, palm superolein and

palm mid fractions can be obtained. The iodine value for

palm superolein is within the range of 6472 whereasiodine values for palm mid fractions have a range of 32

48. Palm superolein has a low cloud point (,3 7C)and can

be used in colder climates. Palm mid fractions contain

mainly 1,3-dipalmitoyl-2-oleoyl-sn-glycerol and lesser

amounts of 1-palmitoyl-2-oleoyl-3-stearyl-sn-glycerol,

are sharp-melting fats and can be used for formulation

into cocoa butter equivalent and confectionery fats.

Similarly, palm stearin can be further fractionated into

very hard stearin and palm mid fractions. The palm mid

fractions obtained from the stearin fraction usually con-

tain too high amounts of tripalmitoylglycerol, but can be

further processed into good-quality palm mid fractions.

By the fractionation process alone (without hydrogena-

tion), very hard palm stearin with iodine values of less than

10 can be achieved. This hard stearin can be used for

interesterification with oleic acid to produce 1,3-dioleoyl-

2-palmitoyl-sn-glycerol. 1,3-Dioleoyl-2-palmitoyl-sn-

glycerol is used in infantformulations, imitating the human

milk.

To overcome the adverse effects of trans fatty acids on

cardiovascular diseases, palm oil and its fractions are

widely used for direct blending with other oils or are

interesterified with other oils to meet the trans-free fat

requirements of the food industry.

Other chemical characteristics of palm oil and its frac-

tions given in Tab. 7 are refractive index, apparent

density, slip melting point and solid fat contents at

various temperatures. These parameters provide infor-

mation on the physical properties of palm oil and itsfractions.

6 Specifications for CPO

In the past, CPO was traded on free fatty acids (5%

maximum) and moisture and impurities (0.25% maximum)

as the contractual parameters. Recently, an additional

parameter, deterioration of bleachability index (DOBI)

value of 2.3 minimum was included. For CPOs future

trading, the free fatty acids and DOBI of CPO to be deliv-

ered into the port tank installations are 4% maximum and

2.5 minimum, respectively.

The DOBI is a unique parameter for CPO and was devel-

oped by the Malaysian Palm Oil Board. It is a ratio of the

absorbance at 446 nm to that at 269 nm. The former

measures the carotene content whereas the latter meas-

ures the secondary oxidation products. The DOBI is a

good indicator for the ease of bleaching of the CPO in the

refinery. The higher the DOBI value, the easier is the CPO

to be refined. A review on DOBI was given by Siew and

Gee [27].


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Tab. 8. PORAM standard specifications for processed palm oil [28].

Products FFA [%] M&I [%] IV M.Pt [7C] Colour [R]

RBD palm oil 0.1 max. 0.1 max. 5055 3339 3 max.Crude palm olein 5 max. 0.25 max. 56 min. 24 max.

RBD palm olein 0.1 max. 0.1 max. 56 min. 24 max. 3 max.Crude palm stearin 5 max. 0.25 max. 48 max. 44 min.RBD palm stearin 0.2 max. 0.15 max. 48 max. 44 min. 3 max.

PORAM, Palm Oil Refiners Association of Malaysia; FFA, free fatty acid, expressed as palmitic acid;M&I, moisture and impurities; IV, iodine value determined by Wijs method; M.Pt, melting point,determined by AOCS Cc 3-25; Colour, colour determined by Lovibond tintometer mode E AF900 orModel D AF702 in 5 cell, in red unit; RBD, refined, bleached and deodorized.

7 Specifications for processed palm oil

The bulk of CPO in Malaysia is processed into RBD palm

oil, RBD palm olein and RBD palm stearin. Smaller quan-tities of crude palm olein and crude palm stearin are also

being produced. Their basic specifications are given in

Tab. 8 [28]. More stringent specifications involving more

parameters are not uncommon. Specifications for speci-

alty and niche products are subjected to negotiations

between buyer and seller.

8 Conclusions

The fatty acids in palm oil triacylglycerols are trans free

and GM free. The bulk of CPO is physically refined. Thesemi-solid palm oil with iodine values around 52 can be

fractionated into a wide range of products with various

iodine values ranging from less than 10 to more than 70.

The trans-free liquid palm olein, palm mid fractions, and

soft and hard palm stearin are excellent materials for

trans-free food formulations and applications. Both the

minor components and fatty acid distribution at the sn-2

position are contributing to the stability and nutritional

value of palm oil and its fractions.

References

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[Received: November 26, 2006; accepted: February 2, 2007]


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