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Year : 2015  |  Volume : 3  |  Issue : 2  |  Page : 99-103

Determination of some polycyclic aromatic hydrocarbons in commercially prepared roasted foods in Oredo Lga of Edo State, South South Nigeria

1 Department of Biochemistry, Renaissance University, Enugu, Nigeria
2 Department of Biochemistry, Renaissance University; Department of Medical Biochemistry, Faculty of Medical Sciences, College of Medicine, University of Nigeria, Enugu, Nigeria
3 Department of Medical Biochemistry, Faculty of Medical Sciences, College of Medicine, University of Nigeria, Enugu, Nigeria

Date of Web Publication14-Jun-2018

Correspondence Address:
Dr. Charles O Ezeh
Department of Medical Biochemistry, Faculty of Basic Medical Sciences, University of Nigeria, Enugu Campus, Enugu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/njecp.njecp_36_15

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Introduction: Polycyclic aromatic hydrocarbons (PAHs) are a group of more than 100 different chemical organic contaminants that are often the by-products of the incomplete combustion of hydrocarbons. They occur naturally when they are released from forest fires and volcanoes. They are also manufactured as a result of human activities that include agricultural burning, driving, working with coal tar, and during food processing such as roasting. PAHs are potentially carcinogenic and mutagenic. Aim: The aim of the present study was to determine the presence and levels of PAHs in some commercially prepared roasted plantain and cocoyam. Materials and Methods: The study was conducted in Oredo LGA of Edo State. The roasted food samples of plantain and cocoyam were prepared and bought from a food vendor in the named local government. The raw samples of these foods were used as controls. About 20 g of each sample was collected in triplicate. The analysis was performed using gas chromatography–mass spectrometry after Soxhlet extraction of the samples and cleanup of the extract. The results were presented as mean + standard error of the mean and analysis carried out using the Student's t-test at 95% confidence level considered at P ≤ 0.05. Results: There were significant levels of some PAHs in some of the roasted food samples analyzed as compared to the raw form. Conclusion: These analyses indicate the presence of PAHs at significant levels in some roasted foods.

Keywords: Hydrocarbons, polycyclic aromatic hydrocarbons, roasted foods

How to cite this article:
Ehigiamusoe P E, Oguazu C E, Ezeh CO, Martins F O. Determination of some polycyclic aromatic hydrocarbons in commercially prepared roasted foods in Oredo Lga of Edo State, South South Nigeria. Niger J Exp Clin Biosci 2015;3:99-103

How to cite this URL:
Ehigiamusoe P E, Oguazu C E, Ezeh CO, Martins F O. Determination of some polycyclic aromatic hydrocarbons in commercially prepared roasted foods in Oredo Lga of Edo State, South South Nigeria. Niger J Exp Clin Biosci [serial online] 2015 [cited 2022 Aug 14];3:99-103. Available from: https://www.njecbonline.org/text.asp?2015/3/2/99/234491

  Introduction Top

The term polycyclic aromatic hydrocarbons (PAHs) refers to a group of over 100 chemicals made up of varying numbers of carbon and hydrogen atoms connected in the ring-like forms.[1] PAHs are formed mainly as a result of pyrolytic processes, especially the incomplete combustion of organic materials during industrial or human activities such as processing of coal and crude oil, combustion of natural gas, including for heating, combustion of refuse, vehicle traffic, cooking and tobacco smoking, as well as natural processes such as carbonization.[2]

PAHs have a relatively low solubility in water but are highly lipophilic. Most of the PAHs with low vapor pressure in the air are absorbed on particles. When dissolved in water absorbed on particulate matter, PAHs can undergo photodecomposition when exposed to ultraviolet light from solar radiation. In the atmosphere, PAHs can react with pollutants such as ozone, nitrogen oxides, and sulfur dioxide yielding diones, nitro- and dinitro-PAHs, and sulfuric acids, respectively. PAHs are also degraded by some microorganisms in the cell.[3]

Their physiochemical properties, vapor pressure, and solubility vary according to their molecular weight. PAHs containing up to six fused aromatic rings are often known as “small” and PHAs containing more than six aromatic rings are called “large” PAHs. PAHs possess high characteristic ultraviolet absorption spectra, although some are fluorescent.[4]

The potential health hazard of PAHs in food has attracted much attention in recent times. PAHs are formed directly in foods as a result of heat processes such as charcoal grilling, roasting, and smoke drying [Figure 1]. In addition, curing, drying, refining, fermentation, and also air pollutants can induce its formation.[5] The presence of variable quantities of PAHs has been reported in different foods categories and beverages including vegetables, fruits, cereals, oils and fat, smoked foods, coffee, and tea.[3],[6] Meat, milk, poultry, and egg will normally not contain high levels of PAH due to rapid metabolism of compounds in the species of origin.
Figure 1: Roasted ripe and unripe plantain

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Contamination of PAHs by intense thermal processing occurs due to generation by direct lipolysis of food nutrients and also due to direct decomposition of PAH from smoke produced from incomplete combustion of different thermal agents. Food components such as fat cause PAHs to be generated through thermal degradation or thermal polymerization. Different thermal processes affect their production quantitatively.[4]

The formation of PAHs [Figure 2] on roasted foods have been observed to be dependent on the distance of the food from the heat source, the fat content of the food, duration of roasting, the temperature used, whether melted fat is allowed to drop unto the heat source, and the type of fuel used.[7]
Figure 2: Chemical structures and names of PAHs. Source: http://www. pirika. com/images/PAH2.jpg

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Although unmetabolized PAHs can have toxic effects, a major concern is the ability of the reactive metabolites such as epoxies and dihydro-diols to bind to cellular protein and DNA. The resulting biochemical disruptions and cell damage lead to mutations, development malfunctions, tumors, and cancer.[4]

Adverse hematological effects have been observed in animals following oral exposure to high doses of PAHs.[2],[8] Aplastic anemia, pancytopenia, a severe reduction in peripheral blood leukocytes, and severe bone marrow depression with almost destruction of pluripotent hematopoietic stem cells have been seen in nonresponsive mice after oral benzo(a)pyrene.[3] Mice that were fed high level of one type of PAH during pregnancy have difficulty reproducing and so did their offspring. These offspring also had higher rates of congenital disabilities and lower body weights.[2]

PAHs cause many adverse effects on different types of organisms including plants, birds, and mammals.[6] Some studies reported that there is a significant positive correlation between lung cancer in humans and exposure to PAHs from exhaust, coke ovens, roofing tar, and cigarette smoke. PAHs have been revealed to be carcinogenic in humans and experimental animals.[7] Research has shown that approximately 90% of cancer occurring in man is of chemical origin. It is probable that PAHs make their contributions in this respect.[8]

The amount of PAHs formed during cooking or processing of foods depends markedly on the conditions used. Simple practices are known to result in a significant reduction of contamination of foods by PAHs as well as by other undesirable contaminants.[9] These may include selecting preferentially lean meat and fishes, avoiding contacts of food with flames for barbequing, using less fat for grilling, and in general cooking at a lower temperature for a longer time. Boiling can significantly reduce the levels of PAH. Fat should not drip down into an open flame sending up a column of smoke that coats the food with PAH, and roasting the food further from the heat source can greatly reduce the formation of PAHs.[10]

  Materials and Methods Top

Samples were as follows:

  1. Raw and roasted ripe plantain
  2. Raw and roasted unripe plantain
  3. Raw and roasted cocoyam.

The roasted samples were commercially prepared and bought from a food vendor in Oredo LGA of Edo State.


In this analysis, about 20 g of sample, thoroughly mixed with anhydrous sodium sulfate (10 g), was Soxhlet extracted with n-hexane (200 ml) for 6 h. The solvent was concentrated to 5 ml in a rotary evaporator under reduced pressure. 0.5M potassium hydroxide (100 ml) in methanol was added, and the mixture was refluxed for 4 h in a water bath at 80°C. After cooling, deionized water (20 ml) was added, and extraction was performed with n-hexane (3 ml × 50 ml). The combined organic extracts were dried over anhydrous sodium sulfate (0.5 g). The decanted extract was evaporated at 40°C in a rotary evaporator under reduced pressure to near dryness dissolved in isooctane (1 ml) for silica cleanup.

The glass column (1.2 cm 3 in diameter) was slurry packed with silica gel (10 g) in dichloromethane and a top layer of anhydrous sodium sulfate (0.5 g). The column was rinsed with n-hexane (40 ml) before use. The extract was transferred unto the column and sequentially eluted with n-hexane (2.5 ml) and n-hexane-dichloromethane 60:40 (30 ml) to give fractions enriched in alkanes and PAHs, respectively. The second eluate was evaporated under reduced pressure to near dryness and replaced with acetonitrile (1 ml) before injection was made. After cleaning up the sample, 1 g was injected into gas chromatograph-mass spectrometer, and the results were displayed on the monitor.

  Results Top

The results were expressed as mean + standard error of the mean, and analysis carried out using the Student's t-test at 95% confidence level with significant level taken at P ≤ 0.05.

  Discussion of Results Top

Smoking usually occurs by thermal pyrolysis in the absence of oxygen. PAHs in smoked food depend on the smoking process. Main factors influencing PAH formation are the type of woods, moisture content, combustion temperature, the degree of smoking, and smoking time.[4],[11] Among these, the temperature of smoking is the most important. This is because the amount of PAHs in smoke formed during pyrolysis increases simultaneously with the smoking temperature. Direct exposure to smoke brings about a higher concentration of PAHs.[4]

The present study was carried out to determine the presence and levels of PAHs in commercially prepared roasted plantain and cocoyam, which have become not only a delicacy but are also frequently consumed food in most parts of the country.

[Table 1] shows the mean values of PAHs present in roasted and raw plantain. As expected, the roasted form contained significant amounts of PAHs as compared to the raw form which contained no detectable quantities of PAHs. Naphthalene, benzo(a) pyrene, and indeno (1, 2, 3-cd) pyrene were detected in appreciable amounts.
Table 1: The mean values of polycyclic aromatic hydrocarbons present in roasted ripe plantain

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The result shown in [Table 2] reveals the presence of PAHs such as naphthalene, benzo(k)fluoranthene, benzo(a)pyrene, naphthalene, benzo(a)pyrene, fluorene, and phenanthrene in roasted unripe plantain. There were no detectable quantities of PAHs in the raw form. It is important to note here that there is an increase in the presence of PAHs in [Table 2] as compared to [Table 1]. This might have been as a result of smoking time, type and composition of woods, oxygen accessibility, and temperature of smoke.[11]
Table 2: The mean values of polycyclic aromatic hydrocarbons present in roasted unripe plantain

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[Table 3] shows the mean values of PAHs obtained for roasted yam. There appears to be a higher increase in the presence and levels of PAHs in this sample, with indeno(1, 2, 3-cd)pyrene being the highest at 22.9696 mg/mg.
Table 3: The mean values of polycyclic aromatic hydrocarbons present in roasted cocoyam

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Reports on previous publications have revealed that PAHs with higher molecular weight (HMW) are more carcinogenic than the PAHs with lower molecular weight.[12] The levels of indeno(1, 2, 3-cd)pyrene which is an HMW PAH [12] were high in all the samples analyzed. Indeno(1, 2, 3-cd)pyrene is known to be highly toxic.[13]

  Conclusion Top

The results of the present study seem to justify the production of PAHs in roasted foods and calls for an immediate intervention by regulatory food bodies to set up safety measures that will control the ways and manners in which commercially foods are prepared.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Elizabeth W, Suzanne MS, Polycyclic Hydrocarbons and Breast Cancer. FACT SHEET #41. Cornell University Program on Breast Cancer and Environmental Risk Factors in New York City; July, 2001.  Back to cited text no. 1
Polycyclic Aromatic Hydrocarbons (PAHs) FACT SHEET. Public Health Service Agency for Toxic Substance and Disease Registry (ATSDR).US Dept of Health and Human Services; Sept, 1996. Available from: http://www.atsdr.cdc.gov/toxfaq.html. [Last accessed on 2015 Aug 25].  Back to cited text no. 2
Hydrocarbons (PAHs) Toxical Chemicals and Environmental Health Risk Where You Live. US National Library of Medicine. Available from: http://www.toxtown.nlm.nih.gov/text_version/chemicals.php?id=80. [Last accessed on 2015 Aug 25].  Back to cited text no. 3
Nisha AR, Dinesh KV, Arivudainambi S, Umer M, Kahn MS. Polycyclic aromatic hydrocarbons in processed meat. A toxicological perspective. Res J Chem Environ 2015;19:72-6.  Back to cited text no. 4
Donata L. Polycyclic Aromatic Hydrocarbons. FACT SHEET. European Union Reference Laboratory Joint Research Center. Institute for Reference Materials and Measurements; 2011.  Back to cited text no. 5
Olabemiwo OM. Levels of polycyclic aromatic hydrocarbons in grilled/roasted maize and plantain sold in Ogbomosho Nigeria. Int J Basic Appl Sci 2013;13:87-93.  Back to cited text no. 6
Dike HO, Adedolapo AA. Presence and levels of polycyclic aromatic hydrocarbons PAHs in staple foods of Nigeria. J Food Public Health 2011;2:50-4.  Back to cited text no. 7
Pashin YV, Bakhitova LM. Mutagenic and carcinogenic properties of polycyclic aromatic hydrocarbons. Environ Health Perspect 1979;30:185-9.  Back to cited text no. 8
Knize MG, Salmon CP, Pais P, Felton JS. Food heating and the formation of heterocyclic aromatic amine and polycyclic aromatic hydrocarbon mutagens/carcinogens. Adv Exp Med Biol 1999;459:179-93.  Back to cited text no. 9
Lijinsky W. The formation and occurrence of polynuclear aromatic hydrocarbons associated with food. Mutat Res 1991;259:251-61.  Back to cited text no. 10
Ajayi AI, Suleiman HT, Dauda BE, Sadiku OS, Aberuagba F. Effects of extraction methods on the polycyclic aromatic hydrocarbon content on smoked catfish species in Niger state of Nigeria. Jordan J Biol Sci 2012;5:71-80.  Back to cited text no. 11
Amos-Tautuwa BM, Inengite AK, Abasi CY, Amirize GC. Evaluation of polycyclic hydrocarbons and some heavy metals in roasted food snacks in Amassoma, Niger Delta, Nigeria. Afr J Environ Technol 2013;7:961-6.  Back to cited text no. 12
Chemical Book CAC Database List INDENO (1,2,3-CD) PYRENE. Available from: http://www.chemicalbook.com/chemicalproduct/property_EN_CB0761644.htm. [Last accessed on 2015 Aug 25].  Back to cited text no. 13


  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]


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