Vol.6, No.5, 323-327 (2014)
http://dx.doi.org/10.4236/health.2014.65047
Health
Assessment of dairy products consumed on the
Arakmarket as determined by heavy metal residues
Mohammad Rezaei1, Hajar Akbari Dastjerdi2, Hassan Jafari3, Ali Farahi4, Arman Shahabi4,
Hossein Javdani4, Hossein Teimoory5, Mohammad Yahyaei6, Ali Akbar Malekirad2*
1
Department of Food Safety and Hygiene, School of Public Health, Tehran University of Medical Sciences (TUMS), Tehran, Iran
Department of Biology, Payame Noor University, Tehran, Iran; *Corresponding Author: Ak_malekirad@yahoo.com
3
Arak University of Medical Sciences, Arak, Iran
4
Department of Veterinary, School of Veterinary, Shahid Bahonar University of Kerman, Kerman, Iran
5
Soren Tech Toos Laboratory, Food & Biotechnology North East Town, Toos Industrial Town, Mashhad, Iran
6
Department of New Sciences and Technologies, Life Science Engineering Group, University of Tehran, Tehran, Iran
2
Received 22 December 2013; revised 27 January 2014; accepted 4 February 2014
Copyright © 2014 Mohammad Rezaei et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In
accordance of the Creative Commons Attribution License all Copyrights © 2014 are reserved for SCIRP and the owner of the intellectual property Mohammad Rezaei et al. All Copyright © 2014 are guarded by law and by SCIRP as a guardian.
ABSTRACT
Dairy products are nutritious drink and can play
a significant part in a healthy diet. The safety of
dairy products decreases with increasing concentration of toxic compounds and environmental pollutants (especially heavy metals). In
the present study, the contamination of Al, Sn,
As, Cd, Hg and Pb in dairy products (pasteurized
milk, yogurt, yogurt drink, cheese) consumed in
Arak, Iran, 2013 was evaluated using inductively
coupled plasma mass spectrometry (ICP-SFMS)
method. To meet the aim, 60 samples of 5 different brands, consisting of pasteurized milk,
yogurt, yogurt drink, cheese (n = 15) were selected and analyzed for heavy metals content.
100% of the samples were positive regarding the
total average and range concentration of Al, Sn,
As, Cd, Hg and Pb in dairy products was 168.25
± 92.2 (30.6 - 356.5), 5.9 ± 4 (1.1 - 16), 3.2 ± 1.95
(0.4 - 8.1), 4.55 ± 2.6 (0.6 - 10.6), 23.15 ± 10.4 (6.8 50.2) and 15.4 ± 8.53 (3.1 - 40.2) µg/kg, respectively. 28.3% (17 of 60 samples) of dairy products samples had lead (Pb) greater than EU limit
and national Iranian standard (20 µg/kg). Statistical analysis indicated except about As in pasteurized milk and cheese there was no significant difference between products in terms of
heavy metals content.
KEYWORDS
Heavy Metals; Milk; Cheese; Yogurt; Food
Copyright © 2014 SciRes.
Safety; ICP
1. INTRODUCTION
Milk and milk products are one of the main sources of
minerals [1] and rich in calcium, phosphorus, vitamins
and proteins [2], also are basic foods in the human diet.
As an excretion of the mammary gland, milk can carry
numerous xenobiotic substances (pesticides, antibiotics,
drugs, heavy metals and various environmental contaminants), which is a risky factor for the health and safety
of the consumer and new chemical medicines and antibiotics have negative side effects [3]. Heavy metals are
essential for correct body metabolism however the ranges
between their effective and toxic levels are small. Heavy
metal contamination raises environmental concerns, such
as entrance on the food chain, which can be potentially
harmful to human’s health. Trace elements are shown to
have a multitude of toxic effects such as acute syndrome
and neurotoxic effects [4,5]. Detection, determination and
comparing of heavy metals in dairy products with standard to determine the safety of them have been a subject
of numerous studies throughout last decades. Malhat et
al. (2012) reported mean levels of 4.404 and 0.288 µg/g
for lead and cadmium, respectively, in cow milk collected from different sites in El-Qaliubiya governorate,
Egypt [6]. Fatima et al. (2005) reported that the Pb was
determined in two UHT samples with concentration
swell below the PTW limit defined by WHO [7]. Studies
performed in the various foods in Arak city, showed that
this area requires more attention to the foodstuff and
regularly monitor pollutants in food [2,8,9]. The aim of
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M. Rezaei et al. / Health 6 (2014) 323-327
this study was to determine the contents of Al, Sn, As,
Cd, Hg and Pb in pasteurized milk, yoghurt, yoghurt
drink and cheese of five brands available in Iran in the
region of Arak 2013.
2. MATERIALS & METHODS
2.1. Chemicals
All the reagents and chemicals Merck (Darmstadt, Germany) were used of analytical grade. De-ionized water
was used throughout the work. Concentrated nitric acid
(65%), were spectroscopic grades Merck (Darmstadt,
Germany).
microwave vessels but well shaken, opened and sampled
by pouring directly from the original container into the
microwavevessel. Added the samples to each vessels and
10 mL of a concentrated HNO3-H2O2 (2:1, v/v) and kept
samples for 10 min at room temperature till the samples
were homogenized, and then placed the vessels in covered PTFE container. This was then heated following a
one-stage digestion programmed at 80% of total power
(900 W), for 3 - 5 min. After cooling, the resulting solutions were evaporated to semidried mass to remove an
excess acid, and then diluted up to 50.0 mL in volumetric
flasks and kept as a stock sample solution [10,11].
3. RESULTS AND DISCUSSION
2.2. Apparatus
ICP-OES measurements were performed using an ICP
spectrometer working in a simultaneous mode.
2.3. Sampling and Analysis
A total of 60 dairy product samples of 5 different
brands included of pasteurized milk, yoghurt, yoghurt
drink and cheese (n = 15) were randomly selected from
local supermarket in Arak city, 2013. Samples were conditioned in sterile plastic container and kept at 4˚C until
analyses that were carried out in same day. Statistical
analysis with SAS software (9.1) was carried out In order
to determine significance difference between product’s
heavy metal content.
2.4. Sample Preparation
Six elements (Al, Sn, As, Cd, Hg and Pb) were determined in each dairy product samples. Prior to analysis
samples must be decomposed with the appropriate
methods procedure with digestcontaining reduced
amounts of carbon residues. In order to minimize the
effects of the organic matrix, closed vessel acid decomposition in microwave oven system was used. Moreover,
it may provide faster, more efficient process and reduce
or eliminate the risk of sample contamination and losses
of analytes. A microwave assisted-acid digestion procedure was carried out, in order to achieve a shorter digestion time and using minimum amount of acid. Duplicate
of 2.0 mL of each dairy product samples were taken into
Levels of heavy metal in dairy products are summarized in Table 1. The results from samples showed that
the pasteurized milk contained (mean ± S.D) of Al, Sn,
As, Cd, Hg and Pb, 135 ± 85.7, 4.8 ± 3.6, 2.3 ± 1.6, 3.95
± 2.3, 21.17 ± 9.6 and 12.5 ± 7.6 µg/l, respectively. Yoghurt drink contained of 157.9 ± 89, 5 ± 3.2, 2.9 ± 1.7, 4
± 2.6, 20.3 ± 8.8 and 14.3 ± 7.6 µg/l, respectively, yoghurt contained of 186 ± 79.4, 6 ± 4, 3.3 ± 2, 4.8 ± 2.6,
23.8 ± 10.9 and 16.6 ± 8.9 µg/l, respectively and cheese
contained of 194.2 ± 109.2, 7.5 ± 4.7, 4.3 ± 2.1, 5.4 ± 2.7,
27.2 ± 11.6 and 18.2 ± 9.6 µg/kg (Table 1). Accordingly,
the highest and least amount of Pb samples was found in
cheese, yoghurt, yoghurt drink and pasteurized milk samples, respectively. Mean and range concentration of Pb in
samples was 18.2 ± 9.6 (3.8 - 40.2), 16.6 ± 8.9 (3.6 - 35),
14.3 ± 7.6 (3.1 - 29) and 12.5 ± 7.6 (3.2 - 27.5) µg/l or kg,
respectively (Table 1). 28.3% (17 of 60 samples) of
dairy product samples had lead (Pb) greater than EU
limit and national Iranian standard (20 µg/kg). The
amounts of lead in the samples, pasteurized milk are the
best and cheeses have the highest levels of contamination.
In the each product manufacturing process, biochemical
content and their concentration can influence the metal
concentrations. It is well known lead has a high affinity
to caseins. In this study cheeses has the highest content
of lead that this can be due to the high concentration of
casein in it [12]. Except for asin pasteurized milk and
cheese there is no significant difference (p < 0.05) there
was no significant difference between products in terms
of heavy metals content (Tables 1 and 2). The results
Table 1. The Comparisons between means of heavy metal content between various dairy products (µg/l).
As
sn
Al
pb
Hg
Cd
Pasteurized Milk
2.28a
4.76a
134.9a
12.5a
21.16a
3.94a
Cheese
4.28b
7.5a
194.18a
18.21a
27.27a
5.4a
Yogurt
3.34ab
6.07a
186.02a
16.56a
23.81a
4.79a
ab
a
157.88
a
a
a
4.06a
1.01
23.61
Yogurt drink
SD
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2.95
0.48
5.09
14.34
2.18
20.35
2.65
0.66
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1
Pasteurized Milk; 2Yogurt; 3Cheese; 4Yogurt drink.
Table 2. Characteristic of the statistical analysis method for dairy product samples (µg/l).
M. Rezaei et al. / Health 6 (2014) 323-327
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M. Rezaei et al. / Health 6 (2014) 323-327
were nearly agreement with [13], that reported Pb and Al
contamination in milk samples 41.8 - 58.7 and 1460 1985 µg∙L−1. [14] also pointed out rate of contamination
in raw milk samples of 15 different area in Iran, about
90% of the samples were less than the newly established
Codex standard (20 ng/ml). Iwegbue et al. (2008) reported that all analyzed pasteurized bovine milk samples
were above the one permitted by the current Brazilian
legislation. In similar following studies in Romania in
different country was reported average concentration of
Pb varied from 2.73 µg/kg in pasteurized milk to 4.05
µg/kg in hard cheese; that Pb were found at concentration
levels less than WHO tolerated values (25 µg/kg/week)
[15]. In dairy products from sheep milk collected in Two
Regions of Southern Italy, chromium was the highest
levels in milk and lead was the highest in fresh, mature
cheese and in ricotta. The compounds detected at the
lowest concentrations were cadmium in milk, fresh and
mature cheese (0.05 µg/g, 0.05 µg/g and 0.06 µg/g) and
chromium in ricotta (0.03 µg/g) [12]. in milk of cattle
and goats for Pakistan, concentration of lead and cadmiumranged from 42.687 ± 0.051 and 0.084 ± 0.003
mg/L, respectively and showed that the residual levels of
Cd and Pb have been found higher in goat milk [16]. in
Egypt, was reported that lead and cadmium contents of
all the cow milk samples were 4.404 and 0.288 µg/g,
respectively [6]. In Pakistan, milk heavy metals (Cadmium, Chromium, Lead and Nickel) concentrations were
found above those normally associated with suitability
for human consumption [17]. Tona et al. (2013) in Nigeria, showed that all the milk and milk products samples
analyzed contained residues of Pb and Cd heavy metals.
heavy metal contamination in raw milk samples exceeded EU limit with percentage of 100% for lead in
Lubuskie Province, Poland [18]. Also, mean levels for
cadmium, lead, and mercury in the breast milk of Saudi
women were 1.732 µg/L, 31.671 µg/L, and 3.1 µg/L,
respectively [19]. Licata et al. (2004) Reported that the
concentrations of Pb in all milk samples in Calabria, Italy were lower than EU limit (0.10 to 9.92 Ag/kg). There
are some difference between our study and others. As a
reason Several factors such as exhaustion gases, industry
wastes and waste waters polluted to the plants affected
on heavy metal level of plant and other edible parts of
feed animals and then, heavy metal is secreted to milk
and subsequently entered individuals through consumption of milk and other dairy products. Also there is no
information about feedstuff given to cows in sampling
regions, but depending on the Planting area for agricultural products (i.e. air pollution, soil, water, etc.), dairy
Production Equipment, Storage and transport containers,
are important supplies of heavy metal contamination. It
seems that the use of stainless steel containers, appropriate packaging and agricultural products grown in soils
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with low heavy metal pollution could play major role in
reduction of heavy metal content in dairy product.
4. CONCLUSION
As regards the fact that the amount of heavy metals in
most of dairy products examined was above EU limit, it is
highly recommended that controlling measures should be
taken promptly to reduce contamination such as implementing a food control systems (i.e. GAP and HACCP),
educating dairy farmers and manufacturers. Additionally,
it is suggested that subsequent studies should be conducted on heavy metals contamination in different stages
of milk preparing and which factors could be involved in
heavy metals contamination. The presence of heavy metals emphasizes the need for regular monitoring and a
more stringent food safety management system (FSMS) in
order to control the heavy metals at the lowest possible
levels.
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