Food Control 35 (2014) 85e93
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Food Control
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Effective reduction of PAH contamination in smoke cured fish
products using charcoal filters in a modified traditional kiln
D.K. Essumang*, D.K. Dodoo, J.K. Adjei
Environmental Research Group, Department of Chemistry, University of Cape Coast, Cape Coast, Ghana
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 February 2013
Received in revised form
19 June 2013
Accepted 25 June 2013
Polycyclic aromatic hydrocarbons (PAHs) contaminations in Ghanaian smoke-cured fish are known to be
in high levels. This may be linked to the recent upsurge of cancer cases among the population because
PAHs are well-known carcinogens. A modified traditional kiln fitted with charcoal filters to remove PAHs
by adsorption from the smoke before it contacted the fish being smoke-cured was designed. Smokecuring was done for 4 h with three most used smoke wood types- in Ghana namely acacia, sugarcane
bagasse and mangroves. The smoking was done with no charcoal filter and compared to smoking with
two types of activated charcoals fitted to the designed traditionally modified kiln. PAHs in smoke-cured
fish samples (n ¼ 108) using the designed system were analysed using Varian GC/MS (3800-GC) system.
The mean total PAHs levels in the experimental smoked fish samples analysed ranged from 212.56 to
472.98 mg/kg in samples smoke cured with e activated charcoal filters. The mean percent reductions
(efficiency of Kiln) were 21e69%. The mean Benzo[a]pyrene levels in all fish cured using the modified
traditional kiln with charcoal filters in place were below the Turkish Codex’s maximum limit of 2.0 mg/kg.
An ANOVA analysis conducted at 95% CL showed statistically significant differences (P < 0.05) in PAH
levels between smoking with no charcoal filters and those with charcoal as filters. No statistical significant differences (P > 0.05) were obtained between the two smoking processes with charcoal filters.
Fish obtained from the modified traditional kiln were of good organoleptic quality (moisture
content < 65% as recommended) and the use of charcoal filters in fish smoking should be encouraged.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Modified traditional kiln
PAHs level reduction
Activated charcoal filters
Smoke-curing
Smoke-cured fish
Moisture content
1. Introduction
Traditional smoke curing of fish is an extensively practiced
preservation process in Ghana. This process has been in practice by
many countries since antiquity (Dore, 1993). Smoke curing of fish is
usually done by a combination of drying and the deposition of
naturally produced chemicals such as phenols, aldehydes, acetic
acids and a range of polycyclic aromatic hydrocarbons resulting
from the combustion of wood (Kramlich, Pearson & Tauber, 1980,
61e67; Serden-Basak, Şengör & Karakoç, 2010; Wilson, 1981, 150e
152). The preservation effect is generally attributed to the antioxidant and antimicrobial properties of phenolic compounds. This
practice is still widely being used with both (modern) controlled
and uncontrolled kilns. Nevertheless, in Ghana, traditional uncontrolled smoke kilns are still widely being used by fish mongers (Nti,
Plahar & Larweh, 2002). It has been estimated that practically all
* Corresponding author.
E-mail
addresses:
kofiessumang@yahoo.com,
dessumang@ucc.edu.gh
(D.K. Essumang), extrajoseph2007@yahoo.co.uk (J.K. Adjei).
0956-7135/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.foodcont.2013.06.045
species of fish available in Ghana can be smoked and it has been
estimated that about 70e80% of the domestic marine and freshwater catch is consumed in the smoked form (Nti et al., 2002). The
traditional kiln works at a wood burning temperature of 300e
700 C and oven temperature usually above 80 C (Nti et al., 2002).
Generation of wood smoke during curing is a typical example of
incomplete combustion, and undoubtedly polycyclic aromatic hydrocarbons (PAHs) are generated and released into the various
smoked products (Philips, 1999; Stolyhwo & Sikorski, 2005). These
PAHs are very well known class of ubiquitous ecotoxicants which are
harmful to human health, with some known to be highly carcinogenic and mutagenic (Yusty & Daviña, 2005; Janoszka, Warzecha,
B1aszczyk & Bodzek, 2004; Kishikawa, Wada, Kuroda, Akiyama &
Nakashima, 2003; Okuda et al., 2006; Tfouni et al., 2007; Vazquez
Troche, Garcia Falcon, Gonzales Amigo, Lage Yusty & Simal Lozano,
2000). According to the latest classification on carcinogenicity of
PAHs by the International Agency for Research on Cancer monograph, it is has been established that benzo[a]pyrene is a definite
carcinogenic (group 1), dibenz[a,h]anthracene is probably carcinogenic (group 2A), whereas naphthalene, benzo[a]anthracene,
chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[j]
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D.K. Essumang et al. / Food Control 35 (2014) 85e93
fluoranthene and indenol[1,2,3-c,d]pyrene are classified as possible
human carcinogens (group 2B), (Essumang, Dodoo & Adjei, 2012;
IARC, 2012). Also wood smoke has been classified as definite carcinogenic (group 1) (Essumang et al., 2012, 2013; IARC, 2012).
The PAHs are lipophilic in nature and usually accumulate in the
fatty tissues of organism and as such are known to be produce from
the fatty tissues of fish during smoking through pyrolysis of fat at
temperatures above 200 C (EC-SCF, 2002), which is favoured at
temperatures above 700 C (Bartle, 1991). Higher levels of PAHs in
smoke cured fish products with its associated high carcinogenic
and mutagenic risks in Ghana have been reported previously by
Essumang et al. (2012). They suggested that, the high PAH levels in
smoke cured fish products consumed in Ghana (Essumang et al.,
2012) may contribute to the astronomical increase in cancer and
cancer related cases amongst Ghanaians (GNA, 2011).
There have been strong pressures on chemical safety for smoked
products from the EU institutions and other institutes in world in
order to produce acceptable smoke fish products. The Codex Alimentarius Commission on contaminants in food, at its 29th session
from 16 to 20 April 2007 established a reflection on reducing levels
of PAHs in food dried and smoked. Also the EU Regulation 1881/
2006 demands a formal setting of new stricter rule on the content
of PAH in smoked products (EC-SCF, 2002).
According to Codex Alimentarius Commission, the code of
practice for the reduction of PAH contamination of food from
smoking and direct drying processes, PAHs contaminations in
smoke cured foods (fish) should be controlled by filtering of the
smoke before it contacts food being processed (CAC, 2009). It
further stated in its sub-section on general principles for
reducing PAH contamination in foods that smoked food producers should be aware and evaluate the conditions responsible
for higher PAHs productions and where possible should control
those conditions to minimize their formation in the final smoked
product (CAC, 2009). It also stated that appropriate design of the
smoking chamber and the whole equipment used in smoke
curing and possible changes in smoking technique like selection
of wood, the use of smoke condensate, adjustment of time and
processing temperature may reduced the amount of PAH formed
during processing (CAC, 2009).
The adsorption technique is extensively used for the removal of
volatile organic compounds from industrial gas streams. The
commonest adsorbents used include activated carbon, alumina,
silica gel, and zeolites. Research has indicated that activated carbon
is the most effective adsorbent for volatile organic compounds
which PAHs are part (Fuertes, Marban & Nevskaia, 2003; Huang,
Kang, Liang & Hao, 2003; Liu, 2006; Mastral et al., 2002a, 2002b).
Chiang, Wey & Yang (2000) used granular activated carbon as
adsorbent to remove BTEX and PAHs from incineration flue gas at
150e250 C. The results indicated granulated charcoal can effectively remove PAHs in gas stream and the main mechanisms for
this removal were condensation and chemical adsorption,
respectively. Liu (2006), concluded that micropore volume on
activated charcoal was the determinant parameter for PAH
removal. Also gaseous PAH removal at various temperatures followed the order 300 C > 200 C > 340 C, and the removal efficiency of the solid-state PAHs increased with increasing
adsorption temperature.
With respect to the high levels of PAHs in Ghanaian smoke cured
fish coupled with the high carcinogenic and mutagenic risk as reported previously (Essumang et al., 2012) and the upsurge in
carcinogenesis (GNA, 2011) in Ghana, it is prudent to finding a new
fish smoking process technique as described by Codex Alimentarius
Commission (CAC, 2009) in its codes to reduce significantly the
levels of PAHs in smoke cured fish products in Ghana. The research
therefore explored designing a modified traditional kiln with filters
based on sorption principles. Other factors like distance between
the fish and smoke generation source (heat source) were also
considered.
2. Material and methods
2.1. Design of modified traditional kiln
The modified traditional kiln was designed in the nature of
Ghana’s traditional metallic kiln that is popularly used by the
people in highly industrialized cities like Tema, Teshie and some
part of Chorkor (James Town), Sekondi and Takoradi. The modified
kiln was fabricated at the University of Cape Coast’s science workshop. It was fabricated with steel sheets metal and pipes and is
cylindrical in shape. The activated charcoal used as adsorbent in the
main smoking chamber and side filtering chambers were supported on 1.5 mm and 0.5 mm galvanized diamond wire mesh
respectively. The kiln was fabricated to have three semi-detached
filtering chambers at the sides containing charcoal as adsorbents;
two on the kiln’s sides (Fig. 1) and one at the back opposite to the air
opening (40 35 cm) of the wood burning Chamber (Fig. 2). The
back filtering chamber has a rectangular open inlet and outlet for
unfiltered and filtered smoke (Fig. 1) respectively. Within the kiln is
a filtering system consisting of afixed bed (1.5 cm height) of activated charcoal, supported on a galvanized diamond wire mesh
(Fig. 1). These are put in place in order to filter the smoke produced
at the wood burning chamber during smoking by removing PAHs
contaminants before they get into contact with the fish to be
smoked. The main principle employed here is that smoke molecules will move away from the high temperature fire zone to
relatively low temperature zones of the side filtering chambers or
would be compelled to move through the inner activated charcoal
bed, thereby adsorbing contaminants like PAHs from the smoke.
The removable side filters enhance easy detachment and change of
spent charcoal from time to time for better adsorption. The total
cost of fabrication for one of this modified kiln as at February 2012
was GHc/ 397.20 (about 162.12 Euros) (Fig. 3).
2.2. Preparation of locally made activated charcoal
Locally made charcoal (hard) were purchased from the Elmina
market. The charcoal was crushed into granulated forms using
mortar and pestle. It was then sieved with two meshes of sizes
3 mm (upper bound) and 2.5 mm (lower bound). This implies a size
of at least 2.5 mm and maximum of <3.0 mm was achieved for the
final grains of charcoal sieved.
2.3. Chemical activation process
The final grains were soaked overnight in concentrated phosphoric acid. The phosphoric acid was then drained off and the
grains of charcoal were heated in furnace at temperature of 600 C
for 6 h. This process is known to create more micropores (<2 nm)
and mesopores (2e50 nm) in the grains for effective adsorption of
VOCs (Strand, 2001). By heating to this high temperature any residual PAHs or VOCs would have been detached and charred from
the surface of the grain charcoals.
2.4. Wood smoke generation
Three different wood (mangrove, sugarcane bagasse and Acacia)
smokes were used for the smoke curing process. These woods were
chosen because of their relatively high usage in smoke-curing of
fish among the Ghanaian coastal communities linked to the quality
of their fish products and also their readily availability in the coastal
D.K. Essumang et al. / Food Control 35 (2014) 85e93
Fig. 1. Longitudinal section of the modified traditional Kiln.
Fig. 2. Side view (longitudinal section) showing the semi circular-like filtering chamber at the back of the modified traditional kiln.
87
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D.K. Essumang et al. / Food Control 35 (2014) 85e93
Fig. 3. (a) and (b) show the various sections of the removable charcoal filter Experimental. (a) A 8.0 8.0 cm removable filter with 0.5 mm metallic mesh at the basement. (b) The removable filter with filled activated charcoal and the fixing gasket
around it.
communities of Ghana. Acacia and mangroves are classified as
hardwoods. Sugarcane bagasse is very abundant in the coastal regions of Ghana especially in the Western, Central and Volta region
of Ghana. Sugarcane bagasse was also used because of its preference for use to achieving attractively coloured and sweet flavoured
smoke cured fish by fish mongers despite the short shelf-life of its
smoke cured products compared to that of the hardwoods
(Essumang et al., 2013).
The temperatures of the fires and oven used were recorded
using PHYWE digital thermometer (PHYWE Systeme GmbH & co,
Göttingen, Germany) at four different points for every 5-min interval of smoking, after initial equilibration for 15 min. This was
done for 1 h within smoke-curing duration. The average temperatures of hardwoods fires used reached 345.9e465.8 C while that of
the bagasse reached 289.5e402.3 C.
2.5. Fish collection, preparation and smoking processes
Four different types of fresh fish samples namely mackerel
(Scomber scombrus), sardine (Sardinella aurita), tuna (Thunnus
antlanticus), and cigar minnows (Decapterus punctatus) were
collected from the Elmina landing beach and subjected to smoking
using the three wood types and the modified traditional metallic
kiln. These fresh marine fish were selected because they are the
most staple fish in the Ghanaian community. The fish were smoked
according to type for a maximum of 4 h until “well done” for a
quality fish product (Essumang et al., 2013). Smoking was done in
three ways for each fish type using a particular wood as smoke
generator. That is smoke curing with
1) Already made activated charcoal
2) Locally made activated charcoal and
3) With no charcoal as filter in the kiln.
% Moisture ¼
The average temperature of the smoke curing chamber containing the racks was above 82 C (i.e. about 83 C when inner
charcoal filter bed was in place and 90 C, when no charcoal bed
was in place). The average temperatures of the inner activated
charcoal filter beds during smoking ranged from 101.5 11.3 C
to 119.3 16.3 C. That of the “locally made” activated charcoal
ranged from 98.5 13.7 to 122.3 11.8 C for all the smoke
curing processes. Whole smoked fish samples of each wood type
were collected after smoke curing for 4 h composited, skin
removed, homogenized according to fish type (n ¼ 5 fish per
homogenate) and smoking type for further preparation and
extraction prior to analysis using the GC/MS. Homogenization
was done for 5 min using stainless steel Heavy Duty blender
(24CB9E, Snijder Scientific, Tilburg, Holland). The average sizes
of the smoke cured fish were 19.56 2.39 cm (sardines),
19.98 1.48 cm (mackerel), 19.27 1.63 cm (cigar minnows)
and 25.77 2.25 cm (tuna). A total of 108 homogenized smoked
fish samples and 12 fresh fish samples (control) were analyzed.
Homogenized Fish samples were kept in amber bottles and
refrigerated at temperatures below 4 C prior to analysis.
2.6. Reagents
All reagents and chemicals were of analytical grade and of
highest purity possible.
Chromatography grade dichloromethane, n-hexane (Purity
(GC) 99.0%, Analytical reagent, UN 1208, EC: 203-777-6, Lot:
K39517278905, Product: 103876Q) and dichloromethane (HPLC
grade, 99.8% purity, UN1593 EC: 200-838-9) used for the
extraction and clean-up were purchased from VWR-BDH
Chemicals Limited UK. Sodium sulphate (Analytical Reagent,
99.4% purity, product: 28114.296, EC label: 231-820-g) and glass
wool were obtained from VWR-BDH PROLABO UK. Column
chromatography Silica gel (mesh: 70-230, Lot no: 0102/073/2,
product: 36020) used to clean up the extract was purchased
from Auro Avenida Export, PVT Ltd (India). Methanol (100%,
Grade: analytical reagent, UN1230, Prod: 20847.320) and potassium hydroxide pellet (Purity: 86.1%, Analytical Reagent,
UN1813, EC: 2151813, Product: 26668.296) used for saponification were purchased from VWR-BDH PROLABO UK. Petroleum
ether (40e60 C) used for crude fat extraction was also obtained
from BDH PROLABO UK. A PAH standard mixture containing 16
PAHs compounds (Purity: 95.9e99.9%, Lot No: LB61945, 47940U) was purchased from SUPELCO-analytical, Bellefonte, PA,
USA. A mixture containing four isotopically labelled PAHs
namely D10-acenaphthalene, D10-phenanthrene, D12-chrysene,
and D10-pyrene used as an internal standard were also purchased from Chemservice, Westchester, PA, USA. Activated
charcoal (0.85e1.7 mm, 10e18 mesh) from Park Scientific
limited, UK and (2.0e2.5 mm) from GATT-KOLLER, Germany,
were used for the filter.
2.7. Dry weight determination (moisture content)
AOAC (1990) method was employed in the determination of the
moisture of the smoke cured fish. The percent moisture was
calculated using the following equation
½ðMass of sample and Na2 SO4 ; gÞeðMass of dried sample; gÞ 100%
Mass of sample; g
(1)
D.K. Essumang et al. / Food Control 35 (2014) 85e93
2.8. Extraction of PAHs
A Soxhlet apparatus consisting of 500 mL round bottom flask, an
extraction chamber, condenser and water circulators were mounted
on temperature controlled heating mantles for the extractions. Ten
gram of the smoked fish powder was homogenized in a mortar with
about 10 g of Na2SO4 until a completely dry homogenate was obtained. The homogenate was carefully transferred into the extraction
thimble made from cellulose. The cellulose thimble containing the
homogenate was then placed in the extraction chamber of the Soxhlet
extractor. A methanol-KOH mixture (50 mL) prepared by dissolving
6 g of KOH in 12 mL distilled water and making it up to the mark with
methanol in 100 mL volumetric flask was added to the homogenate in
the extraction chamber. Soxhlet extractions were carried out using
300 mL dichloromethane. About 2.0 mL of isooctane was added to the
flask as a keeper. Solvent circulation cycles were at an average of 4
cycles per hour and extraction of each sample was done for 24 h. The
extract was cooled to room temperature. The aqueous layer containing the stearate was separated by addition of 100 mL methanole
water mixture (1:4 v/v) using separatory funnel. The organic layer
was washed twice with 50 mL distilled water to removal all remaining
stearates from the organic extracts. The extract was concentrated
using Rotavapor R-114 (BÜCHI-Sibata, Switzerland) at a temperature
of 45 C to about 5 mL. The extracts were further concentrated to
about 1 mL using a stream of an inert nitrogen gas [USEPA, 1996
(Method 3540C); Telli-Karakoç et al., 2002].
2.9. Post-extraction clean-up
The 1 mL concentrated extract was loaded onto a packed silica gel
column. The column used was prepared by loading 10 g of activated
silica gel into a chromatographic column (all the columns used had
uniform internal diameter of 1 mL). About 1 g of anhydrous sodium
sulphate was added to the top of the column. Both ends of the
packed column were plugged with glass wools. The packed column
was then preconditioned with 20 mL (1:3 v/v) dichloromethane/
hexane mixture. The 1 mL concentrated extract was then applied on
top of the column and eluted first with 20 mL hexane to remove nhydrocarbons and the darkest part of the samples. It was then followed with 20 mL dichloromethane/hexane (1:3 v/v) mixture and
the latter was repeated. Prior to analysis, 200 mL of 0.5 mg/mL four
internal standards were added to each of the sample extract and its
triplicates. The volume was then reduced to 1 mL as stated above.
2.10. GC/MS analysis
A Varian GC/MS-3800 GC system with 8400 auto-sampler (mass
data type: centroid) (Varian Inc, Palo Alto, California) was used for
the
analysis.
The
system was
also
equipped
with
40 m 0.25 mm 0.25 mm VF-5ms fused capillary column. Helium
gas was used as the carrier gas. The column head pressure was
maintained at 10psi for 15 min with a constant flow rate of 1.0 mL/
min. The front injector line was maintained at 250 C. Injection
volumes were 2.0 mL in the splitless mode. The column temperature
was initially held at 50 C for 1 min, and ramped to 320 C at a rate
of 20 C/min, and then held at 320 C for 20 min. The mass spectrometer was operated in the ionization mode and spectra were
acquired using a mass range of 45 m/z to 450 m/z and automatic
gain control. SIM acquisition was carried out by comparison of the
base peak of each targeted PAH.
2.11. Analytical quality control
The PAH standard mix was ran to calibrate the instrument and
also along with the sample to ensure accurate reading and results.
89
The analytical precision and recovery of the 16 PAHs were checked
first with NIST standard reference material 1941b which is marine
sediment collected at the mouth of the Baltimore Harbour intended
for use in evaluating analytical methods for the determination of
selected PAHs, PCBs congeners and chlorinated pesticides in marine
sediments and similar matrices like smoked fish powder. To evaluate the instrumental efficiency for the target compounds, recovery
studies were carried out using four deuterated PAHs, namely D10acenaphthene (for naphthalene, acenaphtylene, acenaphthene and
fluorene), D10-phenanthrene (for phenanthrene, and anthracene),
D10-pyrene (for fluoranthene, pyrene and benz[a]anthracene) and
D12-chrysene (for chrysene and the remaining six).
2.12. Statistical analysis
An analysis of variance (ANOVA) in the Microsoft Excel’ Data
Analysis Toolpack was used to ascertain differences in data means.
Further, analysis of variance (ANOVA) at 95% confidence level for
triplicates of smoked fish samples analysed was conducted. The
efficiency of the modified traditional kiln with respect to PAHs
levels in the final products were calculated as follows;
% REDUCTION ¼
Cnoch Cchar
100%
Cnoch
(2)
Where Cnoch is the PAH levels in fish smoke-cured with no charcoal
in place as filter in the kiln and Cchar is the PAH levels in fish smokecured with activated charcoal in place as filter in the Kiln.
3. Results and discussion
3.1. Quality control result
There were statistically no significant differences in the PAHs
results for triplicates of each sample at the 95% confidence level.
The limit of detection (LOD) and quantification (LOQ) for the individual PAHs was 0.10 and 0.30 mg/kg respectively. The regression
coefficient (R2) of the PAH standard mix calibration curves over five
point concentration range of 0.50e10.00 mg/mL ranged from 0.992
to 1.000 (Table 1).
The recovery study conducted using the NIST 1941B analysis
showed good PAH recovery values (66e113%), with an average PAH
recovery value of 83% (Table 2). The values obtained were used to
establish the reliability of the extraction system and the efficiency
of the GC/MS instrument. In fact, The NIST 1941B was used to
establish the reliability of the extraction system as well as the
Table 1
GC/MS Calibration parameters of the PAHs standard at four point concentrations
over a 1.0 mg/mLe10.0 mg/mL range.
Compound
Molecular weight
Regression coefficient (R2)
Naphthalene
Acenaphthyelene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Chrysene
Benz[a]anthracene
Benzo[a]pyrene
Benzo[k]fluoranthene
Benzo[b]fluoranthene
Indeno[1,2,3-cd]pyrene
Benzo[g,h,i]perylene
Dibenz[a,h]anthracene
128
152
154
154
178
178
202
202
228
228
252
252
252
276
276
278
0.999
0.995
1.000
0.994
0.994
0.996
0.996
0.992
0.992
0.999
0.992
0.993
1.000
0.999
0.999
1.000
90
D.K. Essumang et al. / Food Control 35 (2014) 85e93
Table 2
Result of the recovery studies based on NIST 1941B standard reference material (dry
mass basis).
Compound
Mass fraction
expected
(mg/Kg)
Naphthalene
Acenaphthyelene
Acenapthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Chrysene
Benz[a]anthracene
Benzo[a]pyrene
Benzo[k]fluoranthene
Benzo[b]fluoranthene
Indeno[1,2,3-cd]pyrene
Benzo[g,h,i]perylene
Dibenz[a,h]anthracene
848
53.3
38.4
85
406
184
651
581
291
335
358
225
453
341
307
53
95
6.4
5.2
15
44
18
50
39
31
25
17
18
21
57
45
12
Mean mass
fraction
extracted (mg/Kg)
954.6
36.3
26.0
68.1
458.6
140.0
564.0
563.4
265.0
279.4
254.9
226.7
473.5
225.6
222.8
46.7
109
7.3
4.3
3.5
90.7
19.0
97.0
98.9
22
41
55.2
63
13.5
38.1
52.0
10.8
Mean
recovery (%)
113
68
68
80
113
76
87
97
91
83
71
101
105
66
73
88
elution efficiency of the GC/MS instrument since there was no
specific certified reference material for the sample matrix under
study at the time of the analysis.
3.2. Quality of smoke cured fish products from the modified
traditional kiln
Cardinal et al. (2001) recommended that for the purpose of
product preservation and organoleptic effect, industrial specifications for moisture content in the flesh of smoke cured fish products
should be < 65 percent. In this work, the average percent moisture
content in smoke cured fish with the three wood types for 4 h using
the modified kiln with no activated charcoal as filter in place (NOC)
were between 12.98 0.01 and 33.48 0.57 (Table 3). The average
percent moisture of fish smoke cured with the three wood types for
4 h using the modified kiln with filters containing “already made”
activated charcoal in place (ACT) and “locally made” activated
charcoal in place were from 16.68 0.04 to 44.56 0.61 and
14.68 0.58 to 36.10 0.06 respectively (Table 3). These implied
that the smoked fish products from the modified kiln with or
without filters were of good sensory quality since all the moisture
contents in either treatment were quite below 65 percent as recommended (Cardinal et al., 2001).
Goulas and Kontominos (2005) reported that the moisture
content of smoked chum mackerel samples were 58.1 and 59%.
Kolodziejska, Niecikowska, Januszewska and Sikorski (2002) also
reported that moisture content of smoked mackerel was 56.7%.
These results are comparable to the results obtained in this work
and implied the smoked products obtained are of good sensory
quality as far as preservation is concerned (Goulas & Kontominos
2005; Kolodziejska et al., 2002). With the exception of fish
smoked with Acacia (P ¼ 0.03), ANOVA analysis conducted at 95%
CL on the data obtained showed statistically no significant differences (P > 0.05) between smoking with filters in place and without
filter in place with respect to the moisture content (preservation
sensory quality) of the smoked fish product produced in the
modified traditional kiln.
3.3. PAHs levels in fresh fish samples
The PAHs levels in the fresh fish controls ranged from 46.62 to
320.74 mg/kg in tuna to mackerel respectively. The mean levels of
the individual PAHs ranged from below detection limit to a
maximum of 169.68 mg/kg. This maximum value was recorded for
naphthalene in mackerel. For all the samples, naphthalene was the
dominant PAHs measured. Most of the other PAHs were below
detection limit or were found in minute quantity. Stolyhwo and
Sikorski, (2005) stated that fish and marine invertebrates may
naturally contain minute amounts of different PAH absorbed from
the environment. Benzo[a]pyrene levels used for measuring the
safety of foods were below detection limits used. The only exception was sardines which recorded a minute value (0.36 mg/kg).
Rainio, Linko & Routsila (1986) reported that the edible parts of fish
from unpolluted seas generally do not contain detectable amounts
of B[a]P. These imply that the sea where these fish were harvested
from was not polluted. PAHs are known to be lipophilic and usually
accumulate in fatty tissues (EC-SCF, 2002), this may be a contributing factor to the relatively high levels found in mackerel and
sardines which are known to contain higher fat content than in
tuna and cigar minnow (Essumang et al., 2012).
3.4. PAHs in fish smoke cured using the modified kiln
The mean total PAHs levels in the experimental smoked fish
samples analyzed (n ¼ 108) ranged from 517.33 to 751.56 mg/kg;
212.56e472.98 mg/kg; 248.64e454.77 mg/kg in samples smoke
cured with no charcoal filter in place in the kiln; with “already
made” activated charcoal filter in place, and with “locally made”
activated as filter in place respectively to filter the smoke and
remove PAHs contaminant. These are the results after smoking
with the various woods (Tables 4e6). The lower levels of PAHs in
fish smoked cured with the kiln having the charcoal filter in place
compared to that without charcoal filter in place may be attributed
to the fact that charcoals used as filters were able to adsorbed PAHs
in the smoke as it transcends through the filters. This significant
removal of PAHs in the smoke by adsorption which in effect
resulted in the reduction of PAHs in the smoke cured products may
have been possible because of the lower average temperatures of
charcoal filter beds recorded during the smoking (101.5 11.3 C to
119.3 16.3 C and 98.5 13.7 to 122.3 11.8 C for “already made”
and “locally made” activated charcoal respectively). This may be as
a result of the fact that adsorption of such volatile Contaminants
(PAHs) in gas streams by charcoal is highly temperature dependent
and high temperatures above 200 C may result in reduced
adsorption capacity of charcoal and temperatures > 340 may result
in insignificant adsorption (Liu, 2006). Importantly, the significant
adsorption capacities of the charcoal filters used which might have
resulted in reduced PAHs levels in fish smoked could be attributed
to the high micropores volume on charcoals used (Liu, 2006). These
results are comparable to that obtained by Chiang et al. (2000)
where they removed PAHs from incineration flue gas at 150e
250 C. These low levels of PAHs in the fish smoke cured with the
kiln having charcoal filters in place, may partly be attributed to the
fact the inner charcoal bed served as a barrier that adsorbed and
prevented most of the fats dripping from the fish from entering the
fire zone for pyrolysis which may result in release of PAHs back into
fish (EC-SCF, 2002; Essumang et al., 2012). This barrier/fat
adsorption effect of the charcoal may be significant in fish known to
be high in fat like mackerel and sardine (Essumang et al., 2012;
2013) and salmon (Stolyhwo & Sikorski, 2005). The results obtained indicated granulated charcoal and hence the modified
traditional kiln can effectively remove PAHs in smoke and thereby
reducing it levels in smoke cured products.
The low levels of mean total PAH found in this work for smoking
without charcoal filter as compared to that obtained with Chorkor
smoker was noted (Essumang et al., 2013). This could be attributed
to the relatively wider distance (17 cm) between the smoke
generating chamber and the curing chamber since the amount of
D.K. Essumang et al. / Food Control 35 (2014) 85e93
91
Table 3
Percentage moisture (dry weight) content with respect to the filters used in the modified kiln for the four types of fish smoked with three different types of fires (n ¼ 3).
Fish
Acacia
(p ¼ 0.03)
NOC
Mackerel
Sardine
Cigar minnow
Tuna
12.98
13.83
12.99
21.71
Sugarcane bagasse
ACT
0.01
0.02
0.1
0.1
LOC
16.68
16.96
21.82
29.53
0.04
0.01
0.14
0.42
14.68
19. 61
14.49
27.68
NOC
0.58
0.01
0.16
0.40
27.47
27.55
26.66
31.35
(p > 0.05)
ACT
0.10
0.35
0.02
1.30
35.98
23.91
23.56
44.56
Mangrove
LOC
0.70
0.14
0.58
0.61
32.55
29.43
21.27
35.81
(p > 0.05)
NOC
0.18
0.00
0.01
1.04
17.23
17.84
14.90
33.48
ACT
0.09
0.04
0.20
0.57
19.96
23.76
20.56
44.00
LOC
0.36
0.75
0.37
0.11
18.45
23.36
21.03
36.10
0.34
0.27
0.55
0.06
Where NOC means smoking with no charcoal filter in place, ACT means smoking with charcoal filter (already made activated charcoal) in place and LOC means smoking with
charcoal filter (locally made activated charcoal) in place in the modified kiln.
Table 4
Mean PAHs levels (mg/kg) in fish after smoke cured with Acacia for 4 h using the modified traditional kiln (n ¼ 3).
Compound
Naphthalene
Acenaphthyelene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Chrysene
Benz[a]anthracene
Benzo[a]pyrene
Benzo[k]fluoranthene
Benzo[b]fluoranthene
Indeno[1,2,3-cd]pyrene
Benzo[g,h,i]perylene
Dibenz[a,h]anthracene
TOTAL
Mackerel
Sardine
Cigar minnow
Tuna
NOC
ACT
LOC
NOC
ACT
LOC
NOC
ACT
LOC
NOC
ACT
LOC
360.47
39.70
2.24
23.76
77.27
76.43
103.00
ND
ND
44.11
ND
9.60
ND
14.99
ND
ND
751.56
114.59
34.01
63.64
38.73
22.00
ND
23.04
ND
3.55
ND
ND
ND
2.78
5.70
ND
ND
308.05
180.22
41.76
ND
8.57
56.49
7.42
102.00
3.72
ND
ND
ND
ND
ND
ND
ND
ND
400.18
67.30
8.85
71.03
6.78
4.65
4.36
ND
466.31
22.76
28.23
4.33
4.10
ND
ND
ND
ND
688.70
89.98
5.34
0.58
21.42
ND
ND
ND
172.49
ND
ND
ND
ND
ND
ND
28.35
8.76
326.91
217.85
3.17
2.22
45.09
ND
ND
ND
133.38
ND
ND
ND
ND
ND
ND
ND
32.34
434.06
67.33
26.99
0.93
4.85
ND
ND
ND
516.51
4.70
2.27
2.48
ND
1.48
4.40
ND
0.79
632.73
68.59
15.74
0.97
53.88
19.90
12.60
ND
92.31
ND
ND
ND
ND
0.22
0.94
19.33
ND
284.49
225.43
8.61
7.15
2.84
0.66
0.62
ND
207.40
ND
ND
0.49
ND
ND
ND
ND
1.56
454.77
187.83
31.47
8.33
43.73
58.73
59.07
6.03
183.59
11.92
ND
ND
0.34
4.63
1.61
ND
0.82
598.15
48.90
9.63
5.13
3.28
2.45
2.30
ND
389.76
ND
4.71
ND
1.40
1.82
2.83
ND
0.77
472.98
129.13
28.20
11.89
ND
ND
ND
ND
178.63
ND
ND
ND
ND
ND
ND
ND
ND
347.85
Refer to Table 3 footnote for key to abbreviation.
PAHs in smoked product is known to be a function of its proximity
to the smoke generating source (CAC, 2009; EC-SCF, 2002). This
proximity may have not comprised on the preservation and
organoleptic quality of the product obtained after smoke curing
with the modified traditional kiln since the percent moisture in the
products’ edible parts fell far below 65% as proposed by Cardinal
et al. (2001).
Statistically there were significant differences (P < 0.05) in PAH
levels between smoking without charcoal filter and those with
charcoal as filters but no statistical significant differences (P > 0.05)
were obtained between the two smoking processes that made use
of charcoal filters. There were also no statistical significant differences at 95% CL between PAHs levels in various fish species smoked
with a particular wood type (P > 0.05). This implied that the
Table 5
Mean PAHs levels (mg/kg) in fish after smoke cured with Mangroves for 4 h using the modified traditional kiln (n ¼ 3).
Compound
Naphthalene
Acenaphthyelene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Chrysene
Benz[a]anthracene
Benzo[a]pyrene
Benzo[k]fluoranthene
Benzo[b]fluoranthene
Indeno[1,2,3-cd]pyrene
Benzo[g,h,i]perylene
Dibenz[a,h]anthracene
TOTAL
Mackerel
Sardine
Cigar minnows
Tuna
NOC
ACT
LOC
NOC
ACT
LOC
NOC
ACT
LOC
NOC
ACT
LOC
355.34
31.30
27.77
10.12
26.85
25.03
85.86
114.36
ND
3.68
ND
0.27
0.95
ND
ND
ND
681.53
40.19
2.54
14.87
14.11
36.50
26.69
ND
184.92
ND
ND
ND
ND
ND
ND
ND
1.48
321.27
123.47
17.54
11.99
12.15
18.65
20.78
49.63
98.77
ND
ND
ND
ND
ND
ND
ND
ND
352.98
320.63
67.46
13.78
30.56
11.13
55.84
ND
83.86
ND
ND
4.67
ND
ND
3.45
ND
ND
591.37
44.01
9.25
ND
21.78
3.99
3.75
ND
153.47
ND
ND
0.84
1.72
ND
ND
ND
21.34
260.15
183.78
25.03
ND
22.65
3.09
2.99
ND
57.41
ND
ND
1.54
0.79
ND
ND
ND
ND
297.28
228.83
30.20
ND
11.38
ND
ND
6.74
272.40
1.86
5.18
ND
0.64
ND
ND
ND
30.38
587.62
32.26
2.77
4.42
12.75
2.26
2.12
ND
262.12
ND
10.60
ND
1.44
ND
0.96
ND
ND
331.69
96.89
6.36
ND
7.74
ND
ND
2.93
203.91
ND
4.65
ND
ND
ND
ND
ND
20.76
343.24
290.98
17.15
ND
1.05
ND
ND
ND
198.53
ND
0.81
0.47
ND
0.49
ND
ND
19.93
529.41
142.88
38.89
5.68
ND
ND
ND
ND
84.64
ND
ND
ND
1.73
4.68
ND
28.70
14.67
321.87
119.24
14.56
ND
5.02
ND
10.97
ND
103.97
ND
ND
ND
ND
1.56
ND
ND
18.90
274.22
Refer to Table 3 footnote for key to abbreviation
92
D.K. Essumang et al. / Food Control 35 (2014) 85e93
Table 6
Mean PAHs levels (mg/kg) in fish after smoke cured with sugarcane bagasse for 4 h using the modified traditional kiln (n ¼ 3).
Compound
Naphthalene
Acenaphthyelene
Acenaphthene
Fluorene
phenanthrene
Anthracene
Fluoranthene
Pyrene
Chrysene
Benz[a]anthracene
Benzo[a]pyrene
Benzo[k]fluoranthene
Benzo[b]fluoranthene
Indeno[1,2,3-cd]pyrene
Benzo[g,h,i]perylene
Dibenz[a,h]anthracene
TOTAL
Mackerel
Sardine
Cigar minnows
Tuna
NOC
ACT
LOC
NOC
ACT
LOC
NOC
ACT
LOC
NOC
ACT
LOC
343.97
22.79
14.23
31.29
32.71
31.73
30.04
59.22
0.67
ND
0.96
ND
ND
1.78
ND
8.11
577.50
155.77
6.14
20.73
ND
61.57
ND
26.38
77.12
13.88
ND
ND
ND
2.14
3.13
21.27
18.18
406.33
180.58
48.89
ND
39.54
6.80
1.91
ND
130.64
0.61
ND
ND
ND
0.40
ND
ND
5.21
414.57
174.29
ND
37.86
8.89
ND
45.99
10.51
237.60
ND
ND
2.50
ND
1.65
6.42
ND
9.05
534.77
60.45
33.27
7.61
ND
6.38
6.00
ND
234.43
ND
ND
ND
ND
ND
ND
ND
ND
348.14
111.90
25.60
3.24
26.35
ND
ND
ND
183.36
ND
ND
1.78
ND
ND
0.64
35.35
0.91
389.13
48.91
0.52
ND
2.13
15.23
ND
ND
275.25
330.75
ND
ND
0.48
ND
ND
ND
19.73
693.00
46.13
27.83
ND
55.83
ND
ND
ND
62.48
1.28
8.20
ND
ND
ND
6.94
ND
3.87
212.56
114.00
19.75
ND
19.80
10.57
6.19
ND
49.91
3.13
1.83
ND
ND
1.63
2.58
19.25
ND
248.64
228.63
12.53
66.49
ND
ND
ND
ND
134.43
40.75
29.50
0.63
ND
4.37
ND
ND
ND
517.33
269.83
18.62
22.25
17.82
ND
ND
8.63
ND
4.02
8.06
ND
0.49
ND
ND
ND
ND
349.73
168.05
49.52
ND
14.95
24.70
ND
ND
ND
39.47
ND
ND
ND
ND
2.67
ND
12.17
311.54
Refer to Table 3 footnote for key to abbreviation
efficiency of the modified kiln with filters in place in reducing PAHs
levels in its final smoked product is independent of the fish species.
3.5. PAHs removal efficiency of filters in the modified kilns
The efficiency of the modified kiln in reducing PAHs in the final
smoked fish products with respect the charcoal filters used, i.e.
calculated in terms of mean percent reduction in PAHs levels
ranged from 20.9 to 69.3% and 27.2e64.1% for ACT and LOC
respectively. The average mean percent PAH reduction in smoked
fish products ranged from 41.6 to 47.0% and 38.4e45.5% for ACT and
LOC respectively (Table 7). The raw data on percent reduction
showed that the “already made” activated charcoal is more efficient
than the “locally made” activated charcoal in reducing PAHs levels
in the smoke and hence in the smoked fish products. This may be as
a result of the smaller grain sizes of the granulated “already made”
Table 7
Percent reduction in PAHs level in fish smoke cured with modified traditional kiln
with charcoal filters (efficiency).
Fish type
% Reduction (ACT)
% Reduction (LOC)
Acacia
Mackerel
Sardine
Cigar minnow
Tuna
Average
59.0
52.5
55.0
20.9
46.9
46.8
37.0
28.1
41.9
38.4
Mangrove
Mackerel
Sardine
Cigar minnow
Tuna
Average
46.6
58.8
43.6
39.2
47.0
43.6
48.6
41.6
48.2
45.5
Sugarcane bagasse
Mackerel
Sardine
Cigar minnow
Tuna
Average
29.6
34.9
69.3
32.4
41.6
28.2
27.2
64.1
39.8
39.8
Where [NOC], [ACT], [LOC] represent the PAH levels in fish respectively smoked with
no charcoal filter in place, smoked with charcoal filter (already made activated
charcoal) in place and that smoked with locally made activated charcoal filter in
place in the modified traditional kiln.
activated charcoal (ACT) used which enhanced good packing and
availability of relatively large surface area for PAH adsorption than
compared to the large grain sizes of the LOC used. But statistical
analysis conducted on the data using ANOVA at the 95% CL showed
no significant difference (P > 0.05) in reduction efficiency between
the filters used. This implied that the LOC which is readily available
and cheaper to be made by Ghanaians could be adopted in the stead
of ACT which is somewhat costly and inaccessible by the Ghanaian
fish monger.
From the results (Tables 4e6), it was observed that the levels of
most low molecular weight (LMW) PAHs especially naphthalene in
fish smoked with charcoal filters resulted in drastic reduction when
compared to those smoked without charcoal filter. This may be
attributed to the ability of charcoal to adsorb and remove LMW
from the smoke stream at the conditions used and this is comparable to the results obtained by Liu (2006) using activated charcoal.
Similarly, the higher molecular weight (HMW) PAHs also saw significant reduction in fish smoked cured with charcoal filter in place
with most of them recording values below detection, though low as
compared to reduction in LMW PAHs.
The mean levels of B[a]P which is usually used as indicators to
assessing the quality of consumable foods, was measured to range
between below detection limit (ND) to 4.67 mg/kg for fish smoke
cure with NOC when using the modified tradition kiln (Tables 4e6).
This implied that fish obtained from the modified kiln even without
filters in place may be of good quality since levels obtained were
below the European Commission (EC) limit of 5.0 mg/kg. The mean
levels of B[a]P in fish smoke cured with charcoal filters in place (LOC
or ACT) when using the modified tradition kiln ranged from ND e
1.78 mg/kg (Tables 4e6). These levels were also all below the EC limit
of 5.0 mg/kg and even the Turkish Codex maximum limit of 2.0 mg/kg
for B[a]P levels in smoked fish (EC, 2005; Turkish Codex, 2008). The
comparatively low levels obtained for smoke curing with charcoal
filter in place than with NOC may be attributed to the ability of the
granulated charcoal to remove B[a]P from the smoke before getting
into contact with the fish being smoked. Gómez-Guillén, GómezEstaca, Giménez and Montero (2009) and EC-SCF (2002) have recommended that the normal content of benzo[a]pyrene in smoked
fish should be between 0.1 and 1 mg/kg and this is comparable to the
results obtained after smoke curing the fish with the various woods
using the modified traditional kiln containing charcoal filters since
most levels of B[a]P analysed in smoked fish products were within
this range (Tables 4e6). These results may imply that smoked fish
D.K. Essumang et al. / Food Control 35 (2014) 85e93
products from the modified traditional kiln with charcoal filters are
of good quality and may pose little or no risk health when consumed.
This may hence contribute to reduce significantly the number of
cancer and cancer related cases in Ghana as reported by the
oncology department of Ghana Health Service (GHS, 2011).
4. Conclusion
Charcoal used as filters in modified traditional smoking kiln was
effective in removing PAHs from the smoke generated. Hence
smoked fish products obtained from this modified traditional kiln
had reduced PAHs level and may pose little or no health effect on
consumers. Hence the adoption of this fish smoking system in
Ghana may help reduce the levels of PAH-associated health effects
like cancer and other cancer related ailments which is reported to
be on the increase in Ghana, though further research is required.
Acknowledgement
We wish to express our heart-felt appreciation to Mr. Paul OseiFosu of Ghana Standard Authority for his support. We also wish to
show our sincerest gratitude to Auntie Abena of Elmina, a fish
monger who helped by giving her smoking facility and her time in
the smoking of the samples. Our final thanks go to the Government
of Ghana and University of Cape Coast for their financial assistance.
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