Pertanika 12(3), '\77-'\8;; (1989)

Preservation of Oil Palm Fruits: Nonoxidative Effects ofIonizing Radiation on Palm Olein and Crude Palm Oil

K. ENDINKEAUDepartment of Chemistry,

Faculty of Science and Environmental Studies,Univasiti Pertanian Malaysia,

43400 UPM Serdang, Selangor Daml Ehsan, Malaysia.

T.w. WOODWARDDepartment of Chemistry and AjJplied Chemist I)',

University of Salford,Salford M5 4WT England.

Key words : Preservation, oil palm fruits, nonoxidative effects, palm olein, crude palm oil, gamma­irradiation.

ABSTRAKKesan sinamn-gama ke atas olein sawit telah dihaji. Sinamn dengan dos antam 0.1 hingga 1 MGy me­nyebabkan kerosahan he atas asid lemah tah tepu tetapi hampir tidah ada kesan he atas asid-asid lemak teprl.Kesan yang sama didajJati pada sampel yang disimjJan selama 1 dan 2 bulan pada suhu bilik. Sinamnpada 30 hGy juga merosakkan kandungan Iwrotena di dalam mznyak sawit mentah tetapi tidak mem­penganthi kandungan asid lemak bebas. Kajian ini mendap(tti slnamn-gama dapat digunakan untukpengawetan tetajJi tidak sesuai untuk tujuan jJenstelilan buah kelapa sawit.

ABSTRACTThe effect ofgamma-irradiation on jJalm olein has been investigated. Irradiation doses (0.1 to 1 MGj') causedsevere destntction of unsaturated but had little effect on saturated fatty acids. Similar effects were obsemedin irradiated samples stored for 1 and 2 months at room temjJerature. Radiation (uP to 30 kGy) also causedsevere destntction of carotenes in cntde jJalm oil, but had no significant effect on the free fatty acid cont~nt.

Thes~ findings indicate that gamma-mdiation may be used for preservation but not for sterilization of palm

fntits.

INTRODUCTIONOne of the most important tasks of the palm oilproducer is to produce high quality oil. Likeother vegetable oils, palm oil is very susceptibleto hydrolysis by the action of a Lipase enzymewhich is found in palm fruit, fungi and micro­organisms. The hydrolysis reaction causes fatsto split into free fatty acids (f.f.a) and glycerolwhich lead to poor quality oil. A poor qualityoil with more than 10% f.f.a. is sold as a regulargrade, whereas good quality ones should haveless than 5% f.f.a and marketed at a premiumwhich would fetch much higher prices.

During harvesting, and especially whenthe palms get older and taller, the fruit bunchesmay suffer some bruising on falling to theground. The damage may rupture the mem­branes which leads to the lipase gaining accessto the fats. In a bruised and crushed fruit, thefJ.a content reaches 60% within a few hours,

. since the lipase starts acting as soon as the cellequilibrium is disturbed. The fungi not on1yattack the bruised or damaged fruits but alsothe ripe harvested ones on which they grow. Asit is with most crops produced in the tropics,the fruits deteriorate within a few days after

K. ENDINKEAU AND T.W. WOODWARD

harvest. The average shelf-life of ripe palm fruitis about 3 days. The problem is worst at themilling stage where the fruits are usually piledup for several days while waiting for processing.The bruised or over-ripe fruit may be coveredand invaded by moulds or micro-organisms. Theresulting oil will have a high f.f.a content, andpoor quality oils are costly to refine. The fruitmay also be damaged during transportationfrom the plantation to the mill. However, thisproblem is not critical in big plantations wherea good transportation and harvesting system isprovided. But it has a serious effect on smallholders (small plantations) because the har­vested fruits are usually left along the road-sidefor several hours or even days before beingtransported to the mill.

Clearly the bruising of bunches and fungalinfection combined with delays between har­vesting and processing are factors determiningthe quality of oil. In considering these prob­lems, it is thought that radiation may be usedto minimize the action oflipase. The fruit couldbe sterilised by radiation to reduce or to kill themicro-organism or fungi, deactivate enzymesand hence, extend the shelf-life of the ripefruits in their harvested state. At present, thereis no satisfactory method to overcome the prob­lem. The only method being practiced is steamsterilization of the fruits at the processing stage.However, it is also known that radiation willdamage the oil to some extent. Therefore, thisresearch was conducted to investigate the non­oxidative effects of radiation on palm oil.

MATERIALS AND METHODS

MaterialsCrude palm oil (CPO) was supplied by Traf­ford Edible Oil Refinery Ltd., Manchester.Boron trifluoride-methanol (14% wIv)' stan­dard fatty acid methyl esters-FAMES (Cs' CIQ'

C 12, C14 , CIG' C1:6, CIS' CIS:1' C 1S:2' C 1S:3 and C20 )

were purchased from Sigma Chern. Co. at apurity of 99%. The CPO and the standardFAMES were stored at -20°C to avoid deterio­ration. Activated carbon, n-hexane (AR), iso­ocatane (HPLC grade), and phosphoric acid(AR) were obtained from BDH Ltd. Activatedearth (Fulmont) was provided by LaporteIndustries Ltd., England. All other solvents were

of reagent grade and were used without furthepurification.

Prepamtion of SampleSample of palm olein was prepared from crudepalm oil (CPO). Briefly: Sample of CPO (200 g)was treated with activated carbon (20 g) toremove carotenes, according to method of Onget al. (1981). The activated carbon was thenfiltered using a sintered glass no. 3 filter andthe oil was recovered after removal of solvent(diethyl ether) under reduced pressure in arotary evaporator. The carotene-free oil was crys­tallised and fractionated into olein and stearinfractions at 2°C, according to method of Tanet al. (1981). The two fractions were thenseparated by filtration using a precooled sin­tered glass (no 3 filter) and washed with coldhexane. The oil was thus separated into a solid(stearin) and a liquid (olein). After removal ofsolvent by means of a rotary evaporator, theliquid palm olein was obtained and refined using0.15% phosphoric acid (AR, 85 wt%) and 1.5%activated earth (fulmont) at 105°C(Zschau 1981; Shaw et al. 1981). The mix­ture was stirred for 30 mins and filtered toremove activated earth. These processes werecarried out under nitrogen atmosphere. Theoil obtained was stored in a glass bottle undernitrogen at -20°C until used.

Analysis of Fatty Acid Composition of Palm OleinFatty acid composition of palm olein was ana­lysed as methyl ester derivatives. The esters wereprepared according to IUPAC-method 2.301(IUPAC 1979) and Morrison and Smith (1964).The esters were analysed using a gas chromato­graph (Analytical-Instrument, model 92) pro­vided with a flame ionizp.tion detector, coupledto a Spectra-Physics SPA4270 computerised inte­grator. A vitreous silica capillary column (25 mx 0.3 mm id) of BP20 with 0.5 )lm film thick­ness (SGE Ltd) was used. The oven tempera­ture was programmed from 130° to 240°C at aramp rate of 7°C/min, after an initial isothermalperiod of 2 min. and was held for 10 min. afterfinal temperature. The detector and injectorport temperatures were 280°C and 250°C res­pectively. The flow rate of the carrier gas(nitrogen) was 60 cm3/min. The method wascalibrated using a standard mixture of methyl

378 PERTANlKA VOL. 12 NO.3, 1989

PRESERVATION OF OIL PALM FRUITS

esters of known composition and a techniqueof internal normalization was used to quantifythe sample.

Preparation of Sample for IrradiationSamples of palm olein (20 g) were irradiatedil1 small glass tubes (5.5 cm x 3.0 cm) with "f­rays using a 6OCo-gamma source at the Univer­sity of Salford, England. The dose rate (65 Gy/min) was determined by Fricked Dosimetryusing ferrous sulphate solution (Jayson et al.1975). Samples were irradiated at room tem­perature and portions of irradiated samples(about 1 g each) were taken at various timeintervals to give total doses between 0.1 to 1MGy. The tubes were loosely stoppered so thatthe air could diffuse into the sample duringirradiation. The fatty acid profile of irradiatedsamples was determined by gas chromatogra­phy fitted with a BP20 capillary column. Somesamples were stored in the dark at 20°C for 1and 2 months and their fatty acid composition

.were determined as before. The free fatty acid(f.f.a) content of palm olein was determined

immediately after irradiation according toIUPAC-method 2.201 (IUPAC, 1979). For thedetermination of f.f.a., the samples were irra­diated up to 30 kGy.

The effect of y-irradiation on carotenecontent of CPO was also investigated. Samplesof CPO were irradiated and portions of irra­diated samples were withdrawn at different in­tervals of time to give a total dose up to 100kGy. A 1.5% solution of irradiated samples inisooctane (HPLC grade) was then prepared andthe optical density at 446 nm was measuredusing a Pye-Unicam SPl800 spectrophotometerand a 1 cm silica cell.

RESULTS AND DISCUSSIONThe liquid palm olein used in the investigationwas prepared from CPO. Throughout theexperiments, nitrogen gas was maintained abovethe oil sample to minimize oxidation byatmos­pheric oxygen. A fatty acid profile of palm oleinis shown in Table 1 while a gas chromatogramof their methyl esters is presented in Figure 1.The chromatogram shows three significant

TABLE 1Fatty acid compositions of palm olein used in the investigation and

comparison with those of PORlM@

Percentage of palm olein (wt %)

Fatty acid SymbolPresent work PORlM

SATURATED

1. Lauric C12:0 0.1 ± 0.01 0.1 - 0.6

2. Myristic C14:0 0.9 ± 0.04 0.9 - 1.4

3. Palmitic C16:0 39.7 ± 0.5 37.9 - 41.84. Stearic C18:0 4.5 ± 0.3 4.0 - 4.85. Arachidic C20:0 0.5 ± 0.04 0.3 - 0.8

MONOUNSATURATED

6. Palmitoleic C16:1 0.1 ± 0.01 0.1 - 0.37. Oleic C18:1 42.7 ± 0.7 41.2 - 43.6

POLYUNSATURATED

8. Linoleic C18:2 11.3 ± 0.6 10.4 - 13.49. Linolenic C18:3 0.3 ± 0.2 0.1 - 0.6

SAT RATED (%) 45.6

UNSATURATED (%) 54.4

Values represent the mean of two separated determinations. Each determination consists of three set of data from three

injections.

"PORlM : Palm Oil Research Institute of Malaysia.

PERTANIKA VOL. 12 NO.3, 1989 379

K. DJDINKEAL; AND T.W. WOODVVARD

Fig. 1 Gas chromatogram ofpalm olein fatt" acid methylpsteT separated on a BP 20 capillary wlumn (25mx O.3mm id). Program: 13(1'(2 min.) to 24(1'C(10 min.) at 'JOC/min. Caniergas: N

2. Split mtio:

60:1.

peaks which represent three major fatty acidsin palm olein, i.e palmitic (39.7 ± 0.5), oleic(42.7 ± 0.7) and linoleic (11.3 ± 0.6) acids. Therest are minor components, namely lauric, my­ristic, palmitoleic, stearic, lil10lenic and ara­chidic acids. The values obtained in-this experi­ment are within the reported ranges (Tan et at.1981; PORIM 1981).

CH~

Scheme 1

(EFA). They have important nutritional conse­quences and therefore must be provided in thediet. The destruction of these acids by ionizingradiation is a great disadvantage if radiation isto be used for palm fruit preservation or steri­lization. The impact of high energy radiationproduces initially excited triglyceride moleculesand/or ionic triglyceride molecules, followeedby homolytic cleavage which occur randomly atthe carbon-carbon bonds in the fatty acid moietyto produce various compounds, Scheme 1.

The changes 9f fatty acid content in palmolein after irradiation are given in Table 2.Neither the saturated nor the unsaturated filttyacids decreased significantly at low irradiationdoses. Only small changes were observed insaturated components, namely lauric, muristic,palmitic, stearic and monounsaturated oleicacids at 0.1 MGy. These components, as ex­pected, were very resistant to radiation. Fur­thermore, palm olein contains a relatively highconcentration of natural vitamin E which pro­tects against peroxidation (peroxidation leadsto formation of hydroperoxides and subsequentdecomposition of the hydroperoxides destroysfatty acids). The highly unsaturated fatty acids,however, were very sensitive and readily des­troyed by irradiation. The linoleic acid was sig­nificantly reduced after irradiation with 0.1 and1 MGy whilst linolenic acid was completelydestroyed at 1 MGy (Figure 2). Generally, mostsaturated components are increased as a func­tion of irradiation dose whereas unsaturatedcomponents decreased with increasing totaldose. These results are in good agreement withthose reported by Takyi (1981), Kavalam (1969)and Hammer et at. (1979).

Samples irradiated with 0.4 MGyandstored for 2 months at room temperatureshowed a small decrease in linoleic acid but a

. large reduction in linolenic acid content. The

2418

!u~,I'Ih

ilI;IiI.'1

11

"il,I

:1"

"

126

Retention time (minutes)

PAlI'l OLEIN

a

II

I1,I

Ii:\II

:1

'~::,II ,: I:116:' 17

:1

II :1

1

1II :1

II :Iii ! ~

~~~UL--'17 .. '11--__---'-J·11--__-----' -----' --'_

~

'-'U!

It is believed that the peroxidation whichoccurs at low doses and a direct interactionbetween radiation and oil components areresponsible for the d~structionof fatty acids inirradiated samples. ,Some polyunsaturated fattyacids, and especially the co6 acids, nameiy lino­leic and arachidonic acids and the co3 such aslinolenic acid are known as Essential Fatty Acid

380 PERTANIKA VOL. 12 NO.3. 1989

the free fatty acid composition of irradiatedpalm olein.

PRESERVATION OF OIL PALM FRUITS

TABLE 2Fatty acid compositions of irradiated and unirradiated palm olein as determined by Gc.

Dose rate 65 Gy/min.

saturated and monounsaturated componentscontent, however, were not significantly changedduring the same period of storage: In general,the total composition of satured components formation of Free Fatty Acidwere increased whereas the unsaturated ones The free fatty acid (LLa) content is the funda-were decreased in samples stored for one and mental parameter controlling the quality oftwo months, Table 3. It is difficult to correlate palm oil. From the refiners' point of view, palmthe destruction of unsaturated fatty acids with oil with high LLa is highly undesirable becausestorage times. It seems that the conditions of it means losses due to high refining cost andthe experiment played a vital role. Irradiation low market prices. Oil with more than 10% LLain aqueous media, for instance, where the is marketed as ordinary grade, and thus fetchesconcentration of soluble oxygen is high, will a low price. Therefore the change in LLa inincrease the oxygen-exposed surfaces. This irradiated palm oil is a very important factor,permits faster reactions of the radiation-induced if radiation is to be applied for preservation orradicals with oxygen which accelerate the sterilization of palm fruits. In this investigation,destruction of polyunsaturated fatty acid with the palm olein samples were irradiated up tothe formation of peroxide and its breakdown sterilization doses. The formation of fJ.a wasproducts. In this study, the oil was irradiated as determined immediately after irradiation (Figureit was, more or less in its natural form. Due to 3) and reported as percentage of palmitic acidits high viscosity, low oxygen content and high (MW 256). Each value represents the averagepercentage of saturated fatty acids, it may limit of a duplicate determination.the destruction of unsaturated fatty acids upon Radiation may induce the formation ofstorage. Therefore, it might be expected that LLa through the following mechanism: c1eav-post-irradiation storage has very little effect on age of the C-O bond of an excited triglyceride

PERTANIKA VOL. ]2 NO.3, ]989 381

K. Er\DINKEAU A:\ID T.W. WOODV\'ARD

0.28A

1.4B 55

C

0.24C12

1.2 C~4 50 C16

0.20 1.0 45

~ 0.16 [0.8 £

w w40

l'J <.:> <.:>;0 -< -<

i:i 0.12 8 0.6 8 35

~u

~ffi"-

0.08 0.4 30

0.04 0.2 35

~II III (.7 lOll x 10- 2

U ltl 18 4U 67 100 x 10. 2

MGyMGy

Figure 2. (Continued)

0.7D

14 55E F'

0.6 C IGol 12 C IX50 CIXol

0.5 1045

... [ [~ 0.4 40w w w

<.:> '"'" < << 0-

~0- 0.3 ~ 35~ u u

'" ~~ ~0.2 30

0.125

.' .10,2 ·0

0 10 18 40 07 100 x 0 10 18 40 67 lliO x 10- 2

MGy MGyMGy

Figure 2. (Continued)

14 0.35 H 1.4G

C 1802 0.30 C 1803 1.2 C2U12

10 0.25 1.0

[ [ .~

0.20 ~ 0.8

w w w

'" '" '"< < 0.15 <0.6~

0- 0-

W ~ ~u

~u

~ 0.10 ~0.4

0.05 0.2

0 10 18 40 67 100 x 10,2 0 10 18 40 67

MGy MGy MGy

Fig. 2 (A ' I) : F.JJect of gamma-in-adiation on the pmjJortions offatty arids in irradiated jJalm olein. Total dose: 0,]10 1 MGy al dose rale 65 Gy/Illin.

382 PERTANlKA VOL. 12 NO.3, 1989

PRESERVATION OF OIL PALM FRUITS

TABLE 3Post-irradiation effect of gamma-irradiation on fatty acid composition

of irradiated palm olein (wt %). Samples stored at room temperature (21°c)after irradiation with 0.1 and 0.4 MGy. Dose rate 65 Gy/min.

Fatty Acid

Unirrd.(Control)

Just afterirrd.

O.lMGy

month 2 months

0.4 MGy

1 month 2 months

0.2 0.21.0 1.0

43.8 43.85.0 5.00.6 0.6

0.3 0.341.4 41.4

7.7 7.60.1 0.0

50.6 50.6

49.5 49.3

•

R1

R2

RJ3

oII

- 0 - C ­oII

- 0 - CoII

- 0 - CCH2

CH

I

0.1 0.2 0.2 0.20.9 1.0 l.l l.l

39.7 42.3 42.3 42.44.5 4.4 4.4 4.40.5 0.4 0.5 0.6

0.1 0.3 0.3 0.342.7 40.5 40.6 41.1

11.3 10.6 10.4 9.70.3 0.3 0.2 0.2

45.6 48.3 48.5 48.7

54.4 51.4 51.5 51.3

o 0", •

o 10 -~----- ••

._----------------- ..

o \5 .

Q 20 ~~--1-~--'-------'---'

SATURATED

1. C12:02. C14:03. C16:04. C18:05. C20:0

MONOUNSATURATED

6. C16:17. C18:1

POLYUNSATURATED

8. C18:29. C18:3

SATURATED (%)

UNSATURATED (%)

Values represent the mean of duplicate analyses.

383

HO

HOOCR1

o'~_, C - R

O'~ 1

(Free fat ty acid)

-' OOCR3

- OOCR2

cH"I 2

CH

ICH

2

l:1Ject oj gamma-irradiation on the formation offree fatty acid in irradiated palm olein. Dose rate

65 Gy/min.

Fig. 3

molecule due to impact of y-radiation on palmolein produces an acyloxy-free radical whichabstracts a hydrogen atom to form the free fattyacid, Scheme 2.

At preservation doses which are less than1 kGy (Kader 1986) there was no detectablechange in f.f.a content and less than 0.2% wereformed at doses up to 30 kGy which are pro­posed for sterilization (Webb 1985; Diehl1977) . This result showed that sterilization doses Scheme 2. Scission at the acyloxy-methylene bond.

PERTAN1KA VOL. 12 NO.3, 1989

K. ENDINKEAU A 'D TW. WOODWARD

has no significant effect on ffa content of irra­diated palm olein. From this point of view, ra­diation can therefore, be applied to preserveand sterilize palm fruits.

Effect of Radiation on CarotenesPalm oil is rich in carotenes and they are res­ponsible for the orange-red colour of CPO. Anaverage concentration ranging from 500 to 800ppm is observed in palm oil from variousgeographical origins (Goh et at. 1985; Cor­nelius 1977). Carotenes show a strong ab­sorbtion at three wavelengths, 418, 446 and 470nm. The destruction of carotenes by radiationwas monitored at 446 nm, the strongest absorb­tion of the three. The UV absorbtion spectra ofirradiated and unirradiated carotenes in isooc­tane are shown in Figure 4. Optical densities ofirradiated solutions were converted to a 1%

,0/,

solution and expressed as E He' The concentra-tions of carotenes in ppm were then obtainedby multiplying this factor by 383 (a universalfactor) which is based on the molar extinctioncoefficient of pure ~-carotene (Swo­boda 1981).

2.0

l.8

unirrd. s:m.plc

5 . .3 kGy

9. S kG::

SO. -; kG::

o~-L-=::L=:~~~300 3.10 ;>80 ~~(l -1.60 500 5..l-u 5S0

Fig. 4 Changes ofcarotene content in crude palm oil with

i1Tadiation doses. Dose rate 65 Gy/min.

Carotenes are very sensitive to radiation.Itsconcentration was reduced significantly withincreasing irradiation dose. Nearly 50% ofcarotenes were destroyed after irradiation with15 kGy which is less than the recommendeddose range for food sterilisation (30 - 50 kGy)(Diehl 1977). Within the range. of sterilisa­tion doses, about 80% destruction occurred andalmost 100% destruction at doses greater than80 kGy (Figure 5). This result suggests that radia­tion is not suitable to replace steam sterilisationwhich is traditionally used to sterilize palm fruitsto deactivate enzymes and prevent a rapid risein f.fa. Application of higher doses (abovesterilization dose) is very limited, as it causesgreat damage to carotenes. This is very impor­tan t as carotenes have a significant value. Besidesacting as photooxidation inhibitors in palm oil,carotenes have both economic and nutritionalvalues. Being a precusor of vitamin A, it is ahighly valued product and if extracted andmarketed may bring extra revenue and benefitsto the palm oil industry.

Fig. 5 DestlUetion of carotene by gamuw-radiatiun m

Clude palm oil.

However, these results have shown thatradiation may be suitable for palm fruits pres­ervation since this process involves much lowerdoses between 1 to 10 kGy. Infact, a dose of 10kGy is much higher than the dose needed forpreservation under practical conditions.In U.S,under a newly approved regulation (April 1986)only doses up to 1 kGy are permitted forpreservation of fruit and vegetables (Kader1986). Under this condition, the preservationof palm fruits by radiation seems promising. Atsuch doses, only a minor destruction of caro­tenes occurs-less than 5%. In fact, lost of caro-

384 PERTANlKA VOL. 12 NO.3, 1989

PRESERVATION OF OIL PALM FRUITS

tenes by radiation at 1 kGy is very small and lessthan those caused by freezing and heat treat­ment (Bayer et at. 1979).

At present,· the factor(s) responsible forthe destruction of carotenes is not known. Thegradual disappearance ofcarotenes with increas­ing dose indicates that the production of thisfactor is dose dependent. Radiation must causethe production of species (peroxides?, freeradicals? say) and it could be that these speciescause the destruction of carotene.

CONCLUSIONRadiation may be used for preservation of palmfruits since doses for this purpose have nosignificant effect on f.f.a and carotene contentsof palm oil. It is not suitable for sterilization ofpalm fruits if carotenes are desirable. However,if radiation is used for this purpose on anindustrial scale, it is important to find doseswhich minimize carotene losses but produce ahigh quality oil.

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CORNELIUS,J.A. 1977. Palm Oil and Palm KernelOil. Prog. Chem. Fats other Lipids 15 : 5 - 27.

DIEHL, J.F. 1977. Preservation of Food. Radiat.Phys. Chen!. 9 : 193 - 206.

GOH, S.H., Y.M. CHOO and S.H. ONG. 1985. MinorConstituents of Palm Oil. I A mer. Oil Chem. Soc.62 : 237 - 240.

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IUPAC. 1979. Standard Methods for the analysisof Oils, Fats and Derivatives. c.Paguot Ed. IUPACApp. Chern. Div., Commission on Oils, Fats andDerivatives, 6th edn.

jA\SON, G.G., BJ. PARSO sAJ"IDAJ. SWALLOW. 1975.Mechanism of Fricke Dosimeter. Int. J. Radiat.Phys. Chem. 7 : 363 - 370.

KADER, AA. I986. Potential Applications of Ion­izing Radiation in Postharvest Handling of FreshFruits and Vegetables. Food Tee/mol. 40: 117 - 121.

KAVAIA."'l, J.P. and W.W. NAWAR. 1969. Effects ofIonizing Radiation on Some Vegetable Fats. J.A mer. Oil Chem. Soc. 46 : 387 - 390.

MORRlSO , W.R. and L.M. SMITH. 1964. Prepara­tion of Fatty Acid Methyl Esters and Dimethy­lacetals from Lipids with Boron Fluoride­methanol. J. Lipid Res. 5 : 600 - 608.

ONG, S.H., P.L. BOEY, H.S.CH'NG and C.K.001. 1981. A study on Carotene Extractionfrom Palm Oil. Paper presented at the Interna­tional conference on Palm Oil Product Technology inThe Eighties, Kuala Lumpur, Malaysia.

PORIM (Palm Oil Research Institute of Malaysia).1981. Characteristics of Palm Oil and Fraction­ated Products. Paper presented at the Interna­tional Conference ;n Palm Oil Product Technology inthe Eighties, Kuala Lumpur, Malaysia.

SHAW, D.B. and G.K. TRIBE. 1981. Use of Acti­vated Earth in Palm Oil Refining and their Effecton Trace MetalContaminants. Paper presented atthe International conference on Palm Oil Product Tech­nology in The Eighties, Kuala Lumpur, Malaysia.

SWOBODA, PA.T. 1981. UV-VIS Spectrophotom­etric Assays for Palm Oil Quality. Paper presentedat the International conference on Palm Oil ProductTechnology in the Eighties, Kuala Lumpur, Malaysia.

TAKYI, E.E.K. 1981. Preservation of Oil Palm Fruitand Oil Palm Fruit Mesocarp by GammaIrradiation. I Sci. Food Agric. 32 : 941 - 947.

T-\..I\;, B.K. and F.C.H. OH. 1981. Oleins and Stear­ins from Malaysia Palm Oil- Chemical and PhysicalCharacteristics. PORIM Tee/mol., Palm Oil Re­search Institute of Malaysia, No.9.

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(Received 18 Febntary, 1989)

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