Determination of Heavy Metals in Canned Dry-Milk and Fish from
Supermarkets in Addis Ababa, Ethiopia
Kefyalew Muleta
Tetemke Mehari (PhD)1
PRESENTATION OUT LINE
Introduction
Objective
Material and Methods
Results and Discussion
Conclusion and Recommendation
Acknowledgment
2
1. Background
• Food quality depends on the composition and chemical
nature of its components (McElhatton, 2007).
• Minerals such as Cu and Zn which are required up to a
limits.
• The metals Cd and Pb enter food as a result of human
activities, can be harmful to health (Neustacdt et al.,
2007).
3
• Milk and fish might be contaminated due to:
o Feeding of cattle on contaminated feed (for milk)
(Miranda et al., 2005)
o Food processing equipments and canning processing
o Storage condition might favors the leakage of heavy
metal to the foods (Buldini et al., 2002)
4
Background cont…
More than 9 thousands tons of canned fish and 2
thousands tons of canned powder milk are imported
to Ethiopia in a year.
More than 200 supermarkets commercialize canned
dry-milk and fish in Addis Ababa (AABT, 2013).
But no evidence of chemical safety of canned foods.
5
Background cont…
Objective of the Study
1. To determine the concentration of Cadmium, Copper,
Lead and Zinc residues in four brands of canned dry-
milk.
2. To determine the concentration of Cadmium, Copper,
Lead and Zinc residues in four brands of canned fish.
3. To compare the labeled nutritional information to
determined values of the foods.
6
2. MATERIALS AND METHODS
• The study was conducted on canned dry-milk and fish
from supermarkets in Addis Ababa from February to
march, 2013
• Laboratory based cross-sectional study design
• Heavy metals (Cd, Cu, Pb and Zn) and proximate
analysis were done.
7
Sampling Design
Canned foods
Canned dry milk
Abay milk Coast milk Nido milk France lait
Canned fish
Chiara tonno fish
Delight fish
Diamond fish
Nicola fish
8
Canned Dry-Milk Sample
The following four brands of canned dry-milk:
9
No Dry-Milk
Brand
Code
1 Abay milk AM
2 Coast Milk CM
3 France Lait FM
4 Nido Milk NM
Canned Fish-Sample
The following four brands of canned fish:
10
No Fish Brand Code
1 Chiara Tonno CF
2 Delight DF
3 Diamond DIF
4 Nicola NF
Metal Extraction Procedure (Wet Digestion)
Double cans of each brands
Homogenized by stainless homogenizer
Duplicate of 2.00 ± 0.01 g milk sample
Duplicate of 5.00 ± 0.01 g fish sample Mixture of HNO3 and H2O2 in
5:1 ratio
Digested on hot plate at
240 ºc for 4 hours for canned fish
300 ºc for 6 hours for dry-milk
Blank, and Pb and Cd Spiked were run to evaluate the reliability of the
procedures (AOAC, 1990).
Cooled, filtered by whatt-man filter paper and made-up to 50mL
volume
11
Proximate Analysis
• Protein, fat, ash, moisture content analysis were done
according to the AOAC, 2000.;
• Carbohydrate for canned dry-milk were determined by
difference method.
12
Statistical Analysis
• Data analysis was computed using version 20 SPSS
and Microsoft Office Excel 2009 software.
• Range, mean ± SD was used to express the
concentration of each heavy metals and proximate
value.
13
Cont… Statistical Analysis
• Two-side student t-test was used to compare the
nutritional label value to determined once.
• One-way ANOVA was used to test the variability
samples among brands, at 95% confidence level.
14
Instrumental (AAS) Analysis
• All the samples were analyzed for their Cd, Cu, Pb,
and Zn residue level using Flame Atomic Absorption
Spectrophotometer (FAAS) at Debrezeit ARC,
ECAE, and AAEPA.
15
Table 2:The following wave lengths were used for each metals
Heavy Metals Cd Zn Cu Pb
Wavelength (nm) 228.8 213.9 324.8 217
Slit width (nm) 0.5 1.0 1.0 1.0
Coefficient of determination
(R2)
0.99 0.99 0.99 0.99
16
Cont… AAS Analysis
• Concentration working standards were used to
calibrate the AAS at:
• 0.25, 0.5, 1 and 2 mg/L for Cu, Cd and Zn
• 0, 0.5, 1, 2, and4 mg/L were used for Pb
17
18
y = 0.0556x - 0.0161
R² = 0.9919
y = 0.1001x - 0.0183R² = 0.987
y = 0.042x + 0.0064
R² = 0.997
-0.05
0
0.05
0.1
0.15
0.2
0 1 2 3
Ab
sorb
an
ce
Concentration
Fig 3: FAAS Calibration Curve for Cd, Cu and
Zn
Cd
Cu
Zn
y = 0.0244x + 0.0011
R² = 0.9943
0
0.02
0.04
0.06
0.08
0.1
0.12
0 2 4 6
Ab
sorb
an
ce
Concentration
Fig 4: Calibration Standard Curve
for Pb
They obey beer’s law.
Instrument calibration for each metals
Table 3: Limit of detection (LOD) and limit of
quantification (LOQ) in mg/g
19
Blank code Cu Zn Cd
LOD 0.27 5.19 0.23
LOQ 0.91 17.33 0.76
3. RESULTS AND DISCUSSION
Table 1: General information of sampled canned dry-milk
from supermarkets in Addis Ababa, 2013.
Brand
Code
Country of
origin
net wet
(g)
Fat Protein CHO Energy Yield
(Kcal/KJ)
AM Ethiopia 400 28.8 24.5 38.3 510/2130
CM Holland 400 28 26 37.2 510/2140
NM Netherland 400 28.2 24 37.4 508/2120
FM France 375 26.2 26 38.6 494/2067
CHO: Carbohydrate in g/100g
20
Table 4: Comparison of level of heavy metals in four brands of
canned dry-milk from supermarkets in Addis Ababa,
2013.
21
Brand
code
Level of heavy metal in canned dry-milk brands (mg/g in wet-base)
Cu Zn Cd Pb
AM 1.053±0.314ab
21.307±8.796a 0.202±0.309
b 5.374±2.048
a
CM 1.512±0.954a 17.039±3.335
a 1.991±0.47
a 8.077±2.094
a
FM 0.88±0.769ab
16.177±1.528a 1.885±0.336
c 5.921±5.045
a
NM 0.094±0.074b 23.679±1.359
a 1.114±0.878
abc 15.999±8.392
a
AML 10 150 0.2 1.5
ND: Not Detected
AML: Allowable Maximum Limit according to FAO/WHO, 1984 in ppm
At each level of parameter, the mean with different superscript
in the same column are significantly different at P=0.05 level.
Cont……
• The lowest Cd level (0.202 ± 0.309 mg/g) in AM milk
branded is comparable with the values of Cd contents (0.2±
0.008 mg/g) in four brands of unlacquered canned milk
studied in Nigeria by Adams and Happiness (2010) .
• The lowest Pb level (5.921±5.045mg/g) of AM milk brand
from France was lower than Pb value (11.2 + 0.48 mg/g) by
Adams and Happiness, (2010) in Nigeria.
22
• The concentration of Zn, Cd and Pb in all the milk
brands of this study were four to six folds higher than
mean level, 4.92, 0.1, and 0.99 mg/g respectively, in
cow’s whole milk from different areas in Addis Ababa
studied by Gashu et al., 2010).
23
Table 5: Comparison of labeled and observed nutritional value in
percent (wet-base) (mean ± SD in %) of dry-milk from
supermarkets in Addis Ababa, 2013.
Brand
code
Fat Protein Carbohydrate
Determined Labeled Determined Labeled Determined Labeled
AM 5.125 ± 2.136a 28.8
b 16.635 ± 5.393
a 24.5
a 70.516 ± 5.607
r 38.3
s
CM 2.715 ± 0.257h 28
b 8.021 ± 0.199
b 26
c 88.530 ± 4.212
t 37.2
a
FM 3.625 ± 1.25m 26.2
n 17.133 ± 1.753
d 26
e 73.523 ± 2.818
b 38.6
c
NM 3.375 ± 2.213p 28.2
q 16.327 ± 4.267
f 24
g 73.877 ± 6.237
d 37.4
e
At each level of parameter means in the same row with the different superscripts are different at
0.05 significantly level.
24
Table 6: Comparison of labeled and observed energy value (wet-
base) (mean+SD) of dry-milk from supermarkets in Addis
Ababa,2013.
Dry-Brand
code
Energy yield in kcal/g Percent
difference Determined Labeled
AM 394.730 ± 10.201a 510.
b
22.602
CM 410.635 ± 15.998c 510
d
19.483
FM 395.248 ± 7.503e 494
f
19.990
NM 391.191 ± 11.732b 508
a
22.994 Mean values with different superscript in same row are significantly different at 95%.
25
Table 12: General information of the sampled canned fish from
supermarkets in Addis Ababa, 2013.
No. Brand
Code
No. of can Country of origin Packed in Net wet(g)
1 CF 2 Spain Sunflower oil 80
2 DF 2 Vietnam Brine 170
3 DIF 2 Thailand Sunflower oil 185
4 NF 2 Indonesia Vegetable oil 125
26
• All the cans have manufacture and expiration date.
• Three cans were well labeled for their nutritional
values but the DF brand, packed in brine, imported
from Vietnam don’t have labeling for their nutritional
values.
• One of the CF brand packed in sunflower oil
imported from Spain was dented at its sides.
27
Table 13: Concentration of heavy metals (mean± SD and range)
in wet weight base in canned fish from supermarkets
in Addis Ababa, 2013.
28
Samp
le
Code
Packed in Level (mg/g)
Cd Cu Pb Zn
CF Sunflower oil 3.541±2.467a
3.004±1.809
a
6.574±2.899a
33.897±3.670
a
DF Brine 1.863±0.243a
0.68±0.449
b
ND
4.447±1.087a
DIF Sunflower oil 2.174±0.559a
0.319±0.232b
5.185±0.000a
1.976±0.868
a
NF Vegetable oil 0.381±0.274a
0.864±0.1
ab
1.791±0.275a
0.08±.004
a
MTL 0.2 10 1.5 150
In each level of parameter the means with different superscript are significantly different at the 0.05 level.
ND: Not Detected
MTL: Maximum Tolerable Limit according to FAO/WHO 1984.
• The levels of Cd in the four brands of fish were higher than:
– (0.13 ± 0.04 mg/kg) in canned Bluefin tuna Thailand and
– (0.053±0.005 mg/kg) in canned Bluefin tuna Korea,
study by Islam et al., 2010
• But Cd level in all the fish (except the CF) were lower than:
20 mg/g, a study by Tuzen, 2003 in fish from Turkey;
Canned tuna from US (1.9 mgg-1), study in India by
Balakrishnan et al., 2011.29
• The lowest level of Pb (1.791±0.275mg/g) in NF fish
brand from Indonesia which is lower than:
Pb level (2.9 mg/g) in canned tuna fish from Libya
(Voegborlo et al., 1999), and
1.95 mg/g in canned fish from Turkey (Celik and
Oehlenschlager, 2006).
30
• The levels of Cd (1.13 mg/kg) and Pb (2.20mg/kg) in fish
from Hawassa and Ziway lakes (Kiflom, 2011) were
higher than the NF brand from Indonesia.
• The levels of the four heavy metals in CF brand packed
in sunflower oil were relatively higher than the other
three brands.
• This might be due to the dented can may leak heavy
metals to the food.
31
Table 15: Fat, protein (g/g) and energy yield (kcal) content in gram
(mean± SD) (wet-base) of canned fish from supermarkets in Addis
Ababa, 2013
Samp
le ID
sample Fat content Protein content Energy value
Determined Labeled Determined Labeled Determined Labeled
CF 2 32.845 ± 5.909a 21b 6.245 ±1.486a 22.5b 320.659 ±4.773a 279a
DIF 2 18.472 ± 0.555c 9d 12.333±1.234i 27.1j 215.578 ±5.504a 189b
NF 2 21.570 ± 1.530e 18f 5.441 ±0.868a 23b 215.896 ±12.54c 254d
At each level of parameter the mean with different superscript in the same row are significant
different at 0.05 levels.
32
5. CONCLUSIONS AND RECOMMENDATIONS
From this study, it can be concluded that:
1. The canned dry-milk brands determine level of Cd and
Cu residues significantly vary among.
2. All brands were not safe in their Pb level.
3. Only, the AM milk brand from Ethiopia was safe in Cd
level.
33
Cont……. Conclusions
4. The levels of Cu residue s vary among brands of canned fish.
5. The three fish brands, CF, DF and DIF were not safe in their
Cd residue level.
6. But the Cd and Pb level in the NF fish brands and the Pb level
in DF brand were safe.
7. Canned dry-milks were good sources of Zn than canned fish.
8. Labeled and determined nutritional values of NF and DIF fish
brands, and all canned dry-milk brands were different.
34
Recommendations
• Determining the concentration of heavy metals and
nutritional values in canned dry-milk and fish should be
done periodically by the responsible organization to
make sure that imported foods are safe for the public.
35
Acknowledgment
• Addis Ababa University, Center for Food Science and
Nutrition,
• Debrezeit Agricultural Research Center,
• Ethiopian Public Health Institute
36
Thank You !
37http://waset.org/abstracts/33636
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