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Heavy PAHc

47.03.9

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Contamination of coconut oil by PAHThis article is by Tony Swetman,Stafford Head, and David Evans ofthe Process Quality ManagementGroup a/the Natural Resources tnsti-ll/te, University of Greenwich, CentralAvenui!. Chmham Maritime, Chatham,Kent ME4 4TB. United Kingdom. TheNatural Resources Institute providesresearch. consultancy, and trainingservices in the environmental and nal'ural resources sector to supportdevelopment assistance programs.

Copra. the product obtained bydrying fresh coconut kernel toa moisture content which ideal-

ly is close to 6%. is the major rawmaterial for the production of coconutoil The drying processes can exposethe fresh kernel to a variety of poren-rial contaminants including soil. ani-mal excrement. insects. and fungaltoxins. Although many fungal toxinsare potential carcinogens (e.g .. ana-toxin BI).of equal or greater concernfrom a health and safety perspective iscontamination caused by the productsof incomplete fuel combustion. Thecompounds of greatest interest arepolycyclic aromatic hydrocarbons(PM!).

This report covers (a) the differentmethods of coconut oil production inrelation to PAH contamination, and(b) the extent of PAH contaminationin refined and deodorized coconut oilsampled in one Southeast Asian coun-try.

Nature and occurrence of PAHPAH are organic compounds con-taining two or more fused carbo-cyclic rings. They are generallysubdivided into two classes: lightPAH. which have four or fewer ben-zene rings; and heavy PAH. whichhave more than four benzene ringsin their structure. The chemicalstructure of a range of PAH isshown in Figure I. and their relativetoxicity in Table 1.

PAH may be produced by all pro-cesses that involve incomplete com-bustion or pyrolysis. and have beenfound in foods as complex mixturesat levels from approximately ten to

Table 1RelatIve toxicity equivalent factors (TEF) propoaed for Individual PAH"

Compound TEF CI"'"

Dibenzta.hjaruhraoene 5.000 HBenzo(a)pyrene 1.000 HBenz(a)anlhracene 0.100 LBenzo(b)f1uoranlhene 0.100 HBenzo(k)f1uoranlhene 0.100 HAmhrecene 0.010 LBenzo(g.h.i)perylene 0.010 HChrysene 0.010 LAcenaphlhene 0.001 LAcenaphthylene 0.001 LFtuorantnene 0.001 LFluorene 0.001 LNaphthalene 0.001 LPhenanthrene 0.001 L..,...,~ 0.001 L

II Fnxn N'1Sbct. LC.T .• and P.K.I...qoy. R~,~ TtJriI:oIOOfllld f>IID~ 16:290-300(t992).b H., heavy PAH (man: thM rour baIunc rinp). L alip PAH (rour bcnuDc rinpor leu).

Table 2PAH (IJglkg) in virgin edible oliSO

II From Grimmer G .. and A. l-liltlchnndl. Mr:hI_"" H).,I~>St!/j2:2JS (1968): bsum: nuorambene. pyrene,

chtyscne. benz(I)arIllIncaIc: "Sum: bmlO(a)pyrcne ....... !hrme. dibml.(I..h)lntlua=

Oil type

CoconutRapeseedSunflower seedPalm kernelPalmGroundnut (peanut)CottonseedLinseedSoybean

Light PAUb

992.030.166.597.521.121.020.833.318.1

Total PA.H

1.039.034.078.3

102.222.556.422.434.920.0

PAH in vegetable fats and oilsGrimmer and Hildebrandt first drewattention to PAH levels in vegetableoils in 1968 (Table 2).

Although many vegetable oils havebeen shown to contain PAH, coconutoil stands alone in its degree of con-tamination. PAH levels exceeding2.000 J.lglkg have been found in crudecoconut oil. By comparison. reportedPAH levels in other vegetable oilsrarely. if ever. exceed 100 J.lglkg.

Legislation governing PADDuring the past 20 years. Germany hasled the way in European food legislation

several thousand parts per billion.Sources of PAH in foods includeenvironmental contamination, acci-dental contamination during foodprocessing, and thermal treatmentsof varying severity used in prepara-tion and manufacture of foods. Pro-cesses used in food preservation,such as drying by direct heating withair that contains combustion gases,may give rise to PAH in foods. Theuse of direct-fired copra kilns(smoke drying) is a common practicein a number of countries and repre-sents the main source of PAH presentin coconut oil.

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LIGHT PAH (4 benzene rings or less)

Fluoranthene Pyrene" Benz(a)anthracene*

dO &9 ro9I '" I I -e, ""

"" ""Naphthalene Acenaphthene Fluorene*

CD CO ceoPhenanthrene Anthracene Chrysene

09 OX) cxSDHEAVY PAH

Benzofkjfluoranthene" Benzo(b) fluoranthene* Benzo(a)pyrene*

Dibenz(a,h)anthracene'" Benzofg.h.ijperylene"

'" Identified in the HPLC analytical procedure

Figure 1. The chemical structure of some polycyclic .rolMtlc hydll)C8rOons (PAH)

There is undoubtedly a potentialhealth hazard from intake of carcino-genic PAH. Tests in rodents haveinduced tumors of the stomach, and inaddition ovarian, lymphoid, mamma-ry, and hepatic tumors. Therefore, leg-islation is likely to be introduced tocontrol PAH intake. However, sincethese compounds are ubiquitous in theenvironment, safe background limitscannot currently be defined.

It is evident that legislation govern-ing PAH intake is in its infancy. Never-theless, an analogy can be drawn when

foods. According to Article 2 of thisdecree, no food that contains contami-nants in an amount harmful to health,and is particularly toxicologically unac-ceptable, may be marketed. Clearly PAHfall into the latter category.

As yet, however, the most cornpre-hensive proposal regarding PAH limi-tat ion has come from the GermanSociety for Fat Science (DGF). TheDGF proposed a value of 5 fJglkg asthe limit value for heavy PAH and avalue of 25 ug/kg for the sum of bothlight and heavy PAH.

covering PAH contamination. GermanMeat Decree 21.1.1973 limits thebenzo(a)pyrene content of meat to Iug/kg: This limit was subsequentlyadopted in Austria, and in 1988 Euro-pean Union (EU) council directive881388/EEC was issued. This lays downprovisions regarding the use of flavor-ings in foods. In accordance with thisdirective, a maximum limit of 0.03fJglkg benzo(a)pyrene is tolerated infood as a result of these flavorings. Laterthe EU issued Council regulation 315193governing the control of contaminants in

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HEALTH & NUTRITION

r Coconut kc:rIliE1 I~ Disintegrating

I DisinlegfOlled kernel IFrying in CI)C()!1ut oil

Scooping OUI

I Fried disilllegralro kernel I

Drained coconutoil

10 be sold

Draining abovethe draining tank

rOil recyclesto the pan

Drained coconut kernel IIr

1Screw pressing

Crode coconut kernel l I Cake

Figure 2. Flow dlagr.m of the hot 011immersion drying (HOlD) preeeee

comparing PAH to ana toxins. The EUhas implemented a maximum level of20 /AS/kg ufhunxin Bt in animal andhuman foods. If and when a similarlegally binding standard is applied toPAH, this will have a profound impacton the food industry in general, and thecoconut sector in particular,

Removing PAH from vegetable oilsin the refining processThe conventional vegetable oil refin-ing process is carried out in threesteps.

• Neutralization. during which theoil is treated with alkali to removefree fatty acids and gums:

• Bleaching 10 reduce color. usuallyby treatment with bleaching earthand/or activated carbon: and

• Deodorizing to remove odor.achieved by passing live steamthrough the heated oil while it is undervacuum.

The neutralizing process isunlikely to have any effect on PAH.Deodorizing removes some or thelight PAH but has little effect on theheavy PAH. However. the use of thecorrect grade and amount of activat-ed carbon during the bleaching stepcan have a significant effect on PAHreduction. Activated carbon is regu-larly used in oil refineries in Europeto treat oils containing high levels ofPAH. Published results for coconutoil show a reduction from2.600-3,700 Ilg/kg in crude to 2-59ug/kg in refined and deodorized oil.For coconut oil containing high lev-els of PAH (1.000 )Jg/kg and above).the level of activated carbon typical-ly added is 1.5% of the oil charge.The activated carbon is added at thebleaching step together with thebleaching earth. For every kilogramof carbon used. 1.5 kg of oil is lost inthe residue after filtration. With

I

coconut oil containing relatively lowlevels of PAH (100 IJg/kg) theamount of activated carbon can bereduced to 0.1 to 0.2% of the oilcharge weight. Disposal of the spentbleaching earth/carbon mixture canbe a problem.

Provided the correct grade of car-bon is used. this treatment can reducethe level of PAH in refined anddeodorized coconut oil to the limitsuggested by the DGF, i.e .. a maxi-mum of 5 )lglkg for the heavy PAHand 25 )lg/kg for total PAH.

Routes to the manufacture ofcoconut oilCoconut oil usually is manufacturedthrough the preparation of copra fol-lowed by screw-pressing to isolate theoil. Copra is prepared by drying freshcoconut kernel in the sun, in a kiln. orby a combination of the two methods.It takes at least five days of continu-ous sunshine to dry the kemelto a sat-Isfacrory moisture content (8%).

The heat source in a copra kiln isgenerally coconut shell or coconuthusk. Kiln-dried copra usually is pro-duced in direct contact with the prod-ucts of combustion in a processdescribed as "smoke drying." In ThePhilippines this type of dryer is knownas a rapaban. where it is normallyfired by burning husk. The Sri Lankakiln employs coconut shell as a fuel,and. when properly used, can producesatisfactory copra. The Los Banos kilnFrom The Philippines is a more recentdevelopment, which incorporates anefficient burner using coconut shell orcharcoal. The most common indirectdryer is the "kukum" dryer in whichwelded oil drums are employed as aheat exchanger. The use of a heatexchanger generates hot air (uncon-taminated by the smoke) which, in thecase of the kukum dryer, rises throughthe dryer bed by convection. It takesat least 24 hours to make copra in akiln.

Other processes for oil extractionare the hot oil immersion drying(HOlD), or "fry-dry," process and theaqueous method.

The HOlD process is indigenous 10Indonesia and bypasses the copra step.In this process. chopped coconut ker-nel is dried by heating (frying) in a

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709

Table 3PAH content (pgIk:g) in coconut olt derived from different production routes

Di~tdrJing DirK1 dr)"ing Dtrect dr)'ing Indirecl drying HOlD Aquet)Us Sun-drying(llIP11hlln) (Sri Lanka (Los BII.DO!i (kukum)

kiln) dryer)

(number sampled) 23 19 6 , 20 31Fluorene 363 134 152 49 28 54Pyrene 435 192 197 59 35 60Benztajanthracene 86 2' 47 7 8 7Benzo(b )nuornnthene 33 14 23 5 , 3Benzo(k)nuorMthene 13 , 9 I 2 IBenzo(a)pyrene 34 " 19 5 3 3Dibenz(a,h)unlilracene 6 36 , I 2Benzo(g,h,i)perylene 23 17 15 , 3 ITotai 993 399 468 13' 84 131 -60Range 126-2,270 144--L196 129-760 90-181 18-290 78-167

pan of coconut oil al 120-170°C. Thedried product is subsequently screw-pressed to extract the coconut oil. Theflow diagram of a typical HOlD pro-cess is shown in Figure 2.

The aqueous method involvesexpressing the milk from a mixture offinely grated fresh coconut kernel andwater. The resulting milk (or creamseparated from the milk) is then heat-ed to evaporate the water and isolatethe oil. This traditional small-scalemethod is still in use in manycoconut-producing countries.

Scope of the investigationFive samples of coconut oil were ana-lyzed:

(a) from copra prepared bydirect drying (tapahan, Sri Lanka kiln,Los Banos dryer).

(b) from copra prepared by indi-rect drying in a kukum dryer

(c) from sun-dried copra(d) from the HOlD method(e) from the aqueous methodThe samples were obtained from

Indonesia, Sri Lanka, and The Philip-pines.

In addition, ten samples of refinedand deodorized coconut oil originatingfrom a variety of sources within oneSoutheast Asian country were exam-ined.

PAH analysisHPLC instrumentation, The high-per-formance liquid chromatography(HPLC) system consisted of a Shi-

madzu lCIO-AD gradient pump witha Waters 470 scanning fluorescencedetector and a Hewlett-Packard3390A integrator. Sample and stan-dard solutions were applied using aRheodyne 7125 fixed-volume loopinjector (50 Ill) onto a 20 cm x 3 mminternal diameter Chromspher PAH(Chrompack U.K. ltd .. London, Eng-land) column operated at ambienttemperature.

Sample preparation. Coconut oilsamples were dissolved in hexane andthe PAH isolated using solid-phaseextraction as follows: coconut oil (0.3g) was dissolved in 10 mL hexane,then 1.0 mL of the sample solutionwas applied to a 500-mg silica solid-phase extraction cartridge precondi-tioned with 2.0 mt, hexane. The PAHwere eluted with 3.0 mL of 30:70(vet/vel) dichlorornethane in hexane.The PAH extract was then evaporatedto dryness under nitrogen, reconstitut-ed in 500 J.lL of 50:50 (vol/vol) ace-tonitrile/water, and analyzed by HPLC.

HPLC conditio liS. The mobilephase was determined experimentallyand employed a linear acetonitrile/water gradient. from 65-100% ace-tonitrile over 15 minutes, then held for5 minutes at 100% acetonitrile. Thenow rate was 1.0 mUmin. The detec-tor wavelengths were: excitationwavelength 298 nm, emission wave-length 439 nm. Compound identifica-tion was by retention time matchingagainst previously injected standards.PAH were quanti lied by peak height

measurement. Chromatograms of astandard and sample solution aregiven in Figures 3A and 38, respec-tively.

Results and discussionTable 3 records the PAH levels in: (a)oil extracted from copra producedfrom several kiln types in Indonesia,Sri Lanka, and The Philippines: (b)oil produced from the small-scaleaqueous process; and (c) oil fromcommercial HOlD operations inIndonesia.

The results are summarized belowin terms of light and heavy PAH inTable 4.

All the samples examined withinanyone method of preparationshowed a wide range in total PAHcontent. However, on average. PAHlevels were higher in all oils extractedfrom kiln-dried copra than oil derivedfrom either the aqueous process or theHOlD process. The lowest PAH levelamong the kilns was found in oil pro-duced in a kukum dryer. This resultwas expected from an indirectly fireddryer.

Coconut oi.l from a single sampleof sun-dried copra had a total PAHcontent of approximately 60 IJg/kgand this almost certainly is the resultof atmospheric contamination. Simi-Jarly the presence of PAH in copraoriginating from the kukum dryer andaqueous processing and in oil fromaqueous processing also is likely to becaused by atmospheric contamination.

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HEALTH & NUTRITION

A

Figure 3. 3A, chromatogram 01 a PAH atandard; 3B, chromatogram of 8 PAH extract from asample 01 coconut 011(1, tluor.nth.n.; 2, pyrena; 3, IMtnz(a)anthracene; 4, benzo(b)fluo-ranthan.; 5, benzo(k)fluorlnthene; 6, benzo(a)pynme; 7, dlbenz(a,h)anthracan.; and 8,benzo(g,h,l)perylene

, 3

B

2

It is not difficult to envisage traces ofsmoke from the chimney of thekukum dryer being drawn down andentering the dryer bed. Also in thesmall-scale aqueous process, oil isola-lion is usually achieved by boilingdown the coconut milk (or cream)over an open fire with consequentsmoke ingress to the oil.

4

, sibility thai the heating step couldresult in PAH contamination. Howev-er, a series of experiments using fry-ing temperatures up to 180'C underlaboratory conditions gave no indica-tion of PAH formation. It is unlikelythat temperatures encountered duringcommercial frying are high enough toprovide the necessary energy to formPAH. Other workers have investigatedthe degradation products formed dur-ing frying, with some employingextremely aggressive frying condi-tions. None, however, has found anyevidence to suggest any likelihood ofPAH formation during frying. In termsof PAH elimination, the HOlD pro-cess would appear to offer a crediblealternative to the copra route.

Although the HOlD process itselfdoes not contribute to the PAH COIl-tent of coconut oils, the question sur-rounding the origin of the PAH foundin HOlD oils from Indonesia needs tobe addressed. There are three likelyexplanations:

First. there are anecdotal cases oflocal processors partially smoke-dry-ing coconut before completing thedrying process by the HOlD process.In these cases the PAH would arisefrom the initial smoke drying and notfrom the HOlD process itself.

Second, there is the possibility thatthe oil used for frying was derivedfrom the copra direct-drying processand consequently contained a high ini-tial PAH level.

Finally, there is every possibilitythat the HOlD-prepared kernel hasbecome exposed to elevated atmo-spheric PAH levels originating fromthe heat processes within industry andfrom general atmospheric pollution.

PAH levels found in samples ofrefined and deodorized coconut oilretailing in one Southeast Asian COUIl-

try are presented in Table 5. Averagefigures (in ~glkg) for the ten samplesanalyzed are: light PAH, 337; heavyPAH, 13; and total PAH, 350.

These results indicate that the con-ditions for relining and deodorizingbeing employed by some processorsin Southeast Asia do not favor avoid-ing PAH.

l 4

7

, ,

6

7

Where applicable the use of sun-drying for copra preparation is likelyto produce coconut oil with a relative-ly low PAH content. However, under-dried, sun-dried copra (as well as kiln-dried copra) is very susceptible tomold attack and therefore to contami-nation by aflatoxin.

In the HOlD process there is a pos-ConclusionsOf the five routes to the production of

INFORM, Vol. 10, no. 7 (JuIV 1999)

711

TableSPAH content (pglkg) of refined coconut oil obtained within Southeast Asia

Sample reference A B C D E F G H I J Mean

Fluorene 164.9 156.8 160.1 \34.5 115.8 103.4 1[4.4 97.4 86.0 69.1 120.2Pyrene 234.2 230.8 197.1 183.7 182.8 174.0 170.3 153.4 144.1 125.0 179.5Benz(a)anthracene 17.6 20.9 18.1 42.2 73.0 73.9 62.2 22.7 21.2 24.8 37.78enzo(b )fluoranrnene 2.5 3.0 9.6 11.1 2.6 2.3 1.9 5.1 2.9 2.1 4.3Benzo(k)fluoranthene 0.8 0.9 2.4 4.7 0.7 0.6 0.7 1.6 1.4 1.5 1.5Benzotajpyrene 1.5 l.l 7.7 5.5 1.1 1.1 2.6 3.1 2.8 2.0 2.'Dibenz( a,h)anthracene 0.6 1.6 4.3 1.6 2.5 1.1 0.5 1.6 • 7.5 2.4Benzo(g,h,i)pery lene 1.3 0.9 4.7 3.1 1.8 1.6 1.4 1.7 1.6 1.6 2.0TOlal 423.4 416.0 404.0 386.4 380.3 358.0 354.0 286.6 260.0 233.6 350.5• '" nOl de'erminedSoun:e: D. Evaru;. 1997 doclOral thesis, Univ"",,;ly of Greenwich. Uniled Kingdom

INFORM. Vol. 10, no. 7 (July 1999)

coconut oil examined in this study, theHorn process is a promising technol-ogy with the potential for wider com-mercial exploitation. In particular, thebenefits arising from its use includebetter operating conditions for work-ers (it has markedly lower dust andsmoke levels) and production of a bet-ter quality oil (low free fatty acid con-tent, low PAH, and no aflatoxin) andcopra cake (no aflatoxin and lowPAH)

The authors believe that, with care,oil produced by the HOlD methodcould contain low PAH levels. Thismay offer advantages for the future iflegislation on PAH levels in oils isintroduced. The aflatoxin-free advan-tage of the HOlD process alreadyexists since it uses fresh coconut ker-nel and avoids the storage of under-dried copra during which toxigenicmolds can grow.

The capital cost of a HOID plantthat can process the equivalent ofone metric ton of copra per day is145% of the capital cost for a plantof similar throughput operating onpurchased copra. For the HOlD pro-cess to become a viable alternative tothe copra route in countries otherthan Indonesia, it must compete infinancial terms. The copra route(either by sun-drying or using direct-fired kilns) represents the lowest-cost method for manufacture ofcoconut oil. Unless supported by aprice incentive, e.g., a premium forlow-PAH coconut oil, the HOlD pro-cess will struggle to compete on acost basis. Furthermore there is the

Table 4Light and heavy PAH content (pg/kg) in coconut oil derived from d1fferent pro-duction routes

Sample origin Light PAH Heavy PAH Total PAH

Tapahan (direct) 884 109 993Sri Lanka kiln (direct) 350 49 399Los Banos dryer (direct) 396 72 468Kukum dryer (indirect) 115 19 134HOlD 71 13 84Aqueous extraction 121 10 121Sun-dried copra -60

issue of organoleptic acceptance(taste, smell, and texture). Althoughthe HOlD process produces an oilwith low free fatty acid content andlow PAH, it confers a characteristicroasted flavor to the oil. Even withinIndonesia, sales of coconut oil pro-duced by the HOlD process (kilangoil) are declining. This is believed tobe due to consumer preference forbland deodorized oils, such as palmolein or refined coconut oil In othercountries, where coconut oil is con-sumed directly without refining,there is a possibility that there wouldbe consumer resistance to oil pro-duced by the HOlD method.

It is clear from the results present-ed in Table 5 that the conditions forrefining and deodorizing beingemployed by some processors inSoutheast Asia do not favor PAHremoval. Treatment with the correctgrade and amount of activated carbonwould overcome this problem, but thecost would presumably be passed on

to the consumer as part of a higherretail price. The extent to which theseoils containing PAH are a health haz-ard is difficult to assess, but PAH lev-els of the order of 25 pg/kg and abovemust give cause for concern. Thesame concern must surround the con-sumption of unrefined coconut oilderived from copra produced indi.rectly fired dryers of any design.

Acknowledgments

This publication is an output from aproject largely funded by the Euro-pean Commission DaXU STD3 andthe Department for InternationalDevelopment of the United King-dom. The project was managed bythe Natural Resources Institute, Uni-versity of Greenwich, United King-dom, and entailed collaboration withthe following research organizations,all of whom provided invaluablesupport: Indonesia-Institute forResearch and Development of Agro-

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HEALTH & NUTRITION

lead (led) v.t. To guide or conduct by showing the way,route, course...

Encourage your colleagues to get involved. Online membership applications are now availablel

www.aocs.org/appJic99.htm

Based Industry (lRDABI). projectleader. Dr. Ath i S. Herman: SriLanka-University of Pcradeniya.project leader, Prof. Upali Samara-jeewa: The Philippines-Universityof the Philippines-Los Banos(UPLB). project leader. Prof. ErnestoP. Lozada. The European Commis-sion DGXII STD3 and the Depart-ment for International Developmentof the United Kingdom can acceptno responsibility for any informationor views expressed in thispresentation.

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Clark. W.L.. and G.W. Serbia. Safetyaspects of frying fats and oils.Food Tech. 46:84-89. 94 (1991).

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Watson. Analysis of polycyclicaromatic hydrocarbons in UK totaldiets [United Kingdom]. FOOllChem, Tosicol, 2/:569-574(1983).

De vos, R.. W. Van Dokkum. A.Schon ten. and P. de Jong Berkhout.Polycyclic aromatic hydrocarbonsin Dutch total diet samples(1984-1986). Food Chem. Tosicol.28:263-268 (1990).

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Miller. K.• Toxicological Aspects ofFood, Elsevier Applied Science.London. United Kingdom, andNew York. New York, 1987.

Prakesh. S.. Differentiation betweenfood-grade and nonfood-grademineral hydrocarbons by thin-layerchromatography. 1. Assoc. Pub.Anal. 27: 109-112 (1989).

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NfW Wfl'\lU'S ~

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