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