The concentrations of 20 metals (Na, K, Ca, Mg, V, Mn, Fe, Cu, Zn, Cr, Mo, Co, B, Ba, Sr, Ni, Si, Al, Pb, and Cd) in cage-reared hens’ eggs have been determined in this study using inductively coupled plasma atomic emission spectroscopy (ICP-OES). There were significant differences in the metal content depending on the edible part of the egg, with the yolk having the greater concentrations of metals. The daily consumption of eggs (24.3 g/person/day for children and 31.2 g/person/day for adults) contributes to the intake of trace metals, notably Fe (3.8% children, 3.2% women, and 6.5% men) and Zn (4.5% children, 6.6% women, and 4.9% men). In addition, the consumption of eggs does not imply a high contribution of toxic metals.
Hen’s eggs have long been one of the most important foods for man because of their high nutritional value, low cost, and easy preparation [
Average consumption data for the Spanish regional areas indicate that the consumption of eggs in the Canary Islands is 31.5 g/person/day [
Diet is an important source of metals [
The trace elements (Mn, Fe, Cu, Zn, Cr, Mo, and Co) are present in small quantities and are necessary for the adequate development of the physiological functions [
Several enzymes, such as ferroxidases, cytochrome C oxidase, or tyrosinase, contain copper, which is an essential trace metal; however an excess could damage the liver and cause gastrointestinal distress. Iron is one of the most abundant metals and is an essential element that plays an important role in the human organism participating in the oxygen transport in blood and muscle tissue and in redox processes. Regarding zinc functions, this metal is necessary for some biochemical processes such as DNA and RNA synthesis, elimination of free radicals, or the preservation of the integrity of the cell membrane [
Manganese is necessary for bone formation, and it also has a role in carbohydrate metabolism, but Mn in excess is neurotoxic. Molybdenum is an important metal due to it being a cofactor for enzymes [
The toxic metals (V, B, Ba, Ni, Sr, Al, Pb, and Cd) are characterized as having a long biological half life and as lacking a biological function and being accumulative in nature [
Boron does not have a function in the human organism and the adverse effects of an excessive intake of this metal are manifested in reproductive and developmental effects; however, these effects have been shown in experimental animals [
Vanadium (V) is a toxic metal that could produce damage in the liver, kidney, and nervous system. However, the gastrointestinal absorption of V is low in humans [
The compounds of nickel are considered as carcinogens by the International Agency for Cancer Research (IARC). The EFSA has recently reduced the tolerable daily intake (TDI) of nickel from 8
Silicon is a metalloid that, at present, has not been convincingly demonstrated to have a biological function in humans. The adverse effects derived from an excessive intake of silicon from food and water are unknown [
Due to the great importance of the some metals and the properties of hen’s egg, which is a basic food ingredient, this study has been conducted to determine the concentration level of different metals, using, for this purpose, inductively coupled plasma atomic emission spectroscopy (ICP-OES), a multielement analytical technique that has favourable detection limits for refractory elements, a high capacity for simultaneous sequential analysis, and a wide linear range [
The European Regulation (EC) number 1881/2006 sets maximum levels for certain contaminants, such as Pb and Cd, in foodstuffs [
The objectives of this study are to determine the content of 21 metals (Na, K, Ca, Mg, V, Mn, Fe, Cu, Zn, Cr, Mo, Co, B, Ba, Li, Sr, Ni, Si, Al, Pb, and Cd) in fresh eggs of hens kept in cages, differentiating between the edible parts of the egg (yolk and white) and to evaluate the intake of these metals taking into account the intake recommendations and limits for each metal.
A total of 144 fresh eggs from caged hens were used, the samples were comprised of 12 egg boxes with 12 eggs in each box. The samples were separated depending on the edible parts of the eggs: 144 yolk samples 144 egg white samples 144 homogenized egg samples
The samples were collected in local shops on the island of Tenerife (Canary Islands, Spain) from November 2012 to April 2013. They were transported to the laboratory and stored at 4°C until treatment.
Three grams of the separated samples (yolk, egg white, and homogenized egg) were placed in porcelain crucibles that were desiccated for 24 hours in an oven at 70°C. The samples were then subjected to incineration in a muffle furnace with a temperature-time programme of
The laboratory material was previously washed to prevent contamination and to eliminate possible traces of metals. The material was kept for 24 hours in 5% HNO3 and then washed with milli-Q grade deionized water [
The metals were determined by an inductively coupled plasma atomic emission spectrometer (ICP-OES) model ICAP 6300 Duo Thermo Scientific. The instrumental conditions were as follows: approximate RF power, 1150 W; gas flow (nebulizer gas flow, auxiliary gas flow), 0.5 L/min; injection of the sample to the pump flow, 50 rpm; stabilization time, 0 s.
Quality controls were performed to verify the accuracy of the analytical procedure. These controls were based on the study of the recovery percentage obtained with the reference material measured under reproducible conditions. The quality controls with the reference materials were performed following the same incineration process as the samples. The following reference materials were used: SRM 1515 Apple Leaves; SRM 1548a Typical Diet; SRM 1567a Wheat Flour, from NIST (National Institute of Standards and Technology) [
Reference metals and recovery study of the analyzed metals.
Metal | Material | Certified concentration | Obtained concentration | Recovery study% |
---|---|---|---|---|
Na | SRM 1515 apple leaves |
|
|
99.6 |
SRM 1548a typical diet | 8132 ± 942 |
|
98.4 | |
SRM 1567a wheat flour | 6.1 ± 0.8 |
|
99.2 | |
|
||||
K | SRM 1515 apple leaves | 1.61 ± 0.02 |
|
97.8 |
SRM 1548a typical diet | 6970 ± 125 |
|
98.4 | |
SRM 1567a wheat flour | 0.133 ± 0.003 |
|
99.3 | |
|
||||
Ca | SRM 1515 apple leaves | 1.53 ± 0.02 |
|
102.3 |
SRM 1548a typical diet | 1967 ± 113 |
|
99.7 | |
SRM 1567a wheat flour | 0.02 ± 0.00 |
|
101.4 | |
|
||||
Mg | SRM 1515 apple leaves | 0.27 ± 0.01 |
|
98.1 |
SRM 1548a typical diet | 580 ± 26.7 |
|
97.7 | |
SRM 1567a wheat flour | 0.04 ± 0.00 |
|
102.6 | |
|
||||
Fe | SRM 1515 apple leaves | 80.0 ± 0.0 |
|
99.5 |
SRM 1548a typical diet | 35.3 ± 3.77 |
|
101.3 | |
SRM 1567a wheat flour | 14.1 ± 0.5 |
|
98.9 | |
|
||||
Mn | SRM 1515 apple leaves | 54.0 ± 3.0 |
|
101.5 |
SRM 1548a typical diet | 5.75 ± 0.17 |
|
99.3 | |
SRM 1567a wheat flour | 9.4 ± 0.9 |
|
102.4 | |
|
||||
Cu | SRM 1515 apple leaves | 5.6 ± 0.24 |
|
98.9 |
SRM 1548a typical diet | 2.32 ± 0.16 |
|
100.7 | |
SRM 1567a wheat flour | 2.1 ± 0.2 |
|
99.7 | |
|
||||
Zn | SRM 1515 apple leaves | 12.5 ± 0.3 |
|
101.9 |
SRM 1548a typical diet | 24.6 ± 1.79 |
|
98.7 | |
SRM 1567a wheat flour | 11.6 ± 0.4 |
|
102.7 | |
|
||||
Cr | SRM 1515 apple leaves | 0.30 ± 0.00 |
|
97.8 |
|
||||
Mo | SRM 1515 apple leaves | 0.09 ± 0.01 |
|
99.4 |
SRM 1548a typical diet | 0.26 ± 0.02 |
|
98.6 | |
SRM 1567a wheat flour | 0.48 ± 0.03 |
|
99.6 | |
|
||||
Co | SRM 1515 apple leaves | 0.09 ± 0.00 |
|
101.5 |
SRM 1567a wheat flour | 0.006 ± 0.00 |
|
102.4 | |
|
||||
B | SRM 1515 apple leaves | 27.0 ± 2.0 |
|
99.9 |
SRM 1548a typical diet | 4.16 ± 0.04 |
|
101.8 | |
|
||||
Ba | SRM 1548a typical diet | 1.10 ± 0.10 |
|
102.5 |
|
||||
Sr | SRM 1515 apple leaves | 25.0 ± 2.0 |
|
98.3 |
SRM 1548a typical diet | 2.93 ± 0.10 |
|
99.2 | |
|
||||
Ni | SRM 1515 apple leaves | 0.91 ± 0.12 |
|
100.6 |
SRM 1548a typical diet | 0.37 ± 0.02 |
|
102.3 | |
|
||||
V | SRM 1548a typical diet | 0.26 ± 0.03 |
|
100.6 |
SRM 1567a wheat flour | 0.011 ± 0.00 |
|
99.4 | |
|
||||
Al | SRM 1515 apple leaves | 286 ± 9 |
|
99.7 |
SRM 1548a typical diet | 72.4 ± 1.52 |
|
98.3 | |
SRM 1567a wheat flour | 5.7 ± 1.3 |
|
99.2 | |
|
||||
Pb | SRM 1515 apple leaves | 0.47 ± 0.02 |
|
100.3 |
SRM 1548a typical diet | 0.044 ± 0.000 |
|
98.9 | |
SRM 1567a wheat flour | <0.02 | <0.02 | 99.5 | |
|
||||
Cd | SRM 1515 apple leaves | 0.014 ± 0.00 |
|
99.3 |
SRM 1548a typical diet | 0.035 ± 0.015 |
|
102.2 | |
SRM 1567a wheat flour | 0.026 ± 0.002 |
|
98.4 |
Detection and quantification limits.
Metal | Wavelength (nm) | Detection limit (mg/kg) | Quantification limit (mg/kg) |
---|---|---|---|
Al | 167.0 | 0.033 | 0.100 |
B | 249.7 | 0.025 | 0.100 |
Ba | 455.4 | 0.008 | 0.042 |
Ca | 317.9 | 4.833 | 16.29 |
Cd | 226.5 | 0.003 | 0.008 |
Co | 228.6 | 0.005 | 0.017 |
Cr | 267.7 | 0.025 | 0.067 |
Cu | 327.3 | 0.033 | 0.100 |
Fe | 259.9 | 0.017 | 0.042 |
K | 769.9 | 4.708 | 15.70 |
Mg | 279.1 | 4.858 | 16.19 |
Mn | 257.6 | 0.017 | 0.067 |
Mo | 202.0 | 0.006 | 0.017 |
Na | 589.6 | 9.142 | 30.46 |
Ni | 231.6 | 0.006 | 0.025 |
Pb | 220.3 | 0.003 | 0.008 |
Si | 185.0 | 0.017 | 0.050 |
Sr | 407.7 | 0.006 | 0.025 |
V | 310.2 | 0.008 | 0.042 |
Zn | 206.2 | 0.017 | 0.058 |
Statistical analysis was performed using the statistical package IBM Statistics SPSS 22.0 (Statistical Package for the Social Sciences). In order to test the normality of the analyzed data, the Kolmogorov-Smirnov and Shapiro-Wilk tests were performed [
Table
Mean concentration ± standard deviation of the studied metals in fresh cage reared hens (mg/kg).
Metal | White |
Yolk |
Homogenized egg |
---|---|---|---|
Ca |
|
|
|
K |
|
|
|
Na |
|
|
|
Mg |
|
|
|
Fe |
|
|
|
Mn | <LOQ |
|
|
Cu |
|
|
|
Zn |
|
|
|
Cr |
|
|
|
Mo | <LOQ |
|
|
Co | <LOQ | <LOQ | <LOQ |
B |
|
|
|
Ba |
|
|
|
Sr |
|
|
|
Ni |
|
|
|
V |
|
|
|
Si |
|
|
|
Al |
|
|
|
Pb |
|
|
|
Cd | <LOQ | <LOQ | <LOQ |
The highest concentration of metals was found in the egg yolk, where the highest levels of K, Ca, Fe, Mn, Cu, Zn, Mo, Ba, Sr, Ni, and Pb were recorded, whereas the levels of B, Si, and Al were the highest in the egg whites. Finally, the homogenized egg samples had the highest concentrations of Na, Mg, Cr, and V. Na was the macroelement found in greater proportions in the egg white, with levels of 1092 mg/kg, followed by
Furthermore, Si was the most abundant trace element in egg whites with a concentration of 18.03 mg/kg; the rest of the trace elements were found in the following sequence
Significant differences (
As regards toxic metals, European legislation does not establish any limits on toxic metals in hen’s eggs.
Table
Comparison of metal concentrations in hen eggs from nonspecified breeder system.
Comparison of metal concentration levels in the egg whites
Metal | Souci et al. [ |
CESNID [ |
Moreiras et al. [ |
Giannenas et al. [ |
Demirulus [ |
This study (2015) |
---|---|---|---|---|---|---|
Ca | 110 | 60 | 50 | — | — | 78.3 |
Cr | — | — | — | 0.048 | — | 0.02 |
Cu | 1.3 | — | — | 0.212 | 7 | 1.69 |
Fe | 2 | 1 | 1 | — | — | 1.46 |
K | 1550 | 1420 | 1500 | — | — | 541 |
Mg | 120 | 100 | 110 | — | — | 81.2 |
Na | 1700 | 1600 | 1900 | — | — | 1092 |
Ni | — | — | — | 0.064 | 3.7 | 0.03 |
Pb | — | — | — | — | — | 0.02 |
V | — | — | — | 0.013 | — | 0.12 |
Zn | 0.2 | Traces | 1 | 1.003 | 7.4 | 0.92 |
Comparison of metal concentration levels in the egg yolks
Metal | Souci et al. [ |
CESNID [ |
Moreiras et al. [ |
Giannenas et al. [ |
Demirulus [ |
This study (2015) |
---|---|---|---|---|---|---|
Ca | 1400 | 1370 | 1300 | — | — | 775 |
Cr | — | — | — | 0.066 | — | 0.12 |
Cu | 3.5 | — | — | 1.357 | 10.5 | 3.21 |
Fe | 70 | 55 | 61 | — | — | 18.6 |
K | 1400 | 970 | 1200 | — | — | 628 |
Mg | 160 | 130 | 150 | 75.96 | — | 31.7 |
Mn | 0.5–2 | — | — | 0.836 | 1.9 | 0.36 |
Mo | — | — | — | 0.26 | — | 0.07 |
Na | 500 | 500 | 500 | — | — | 307 |
Ni | — | — | — | 0.063 | 1.7 | 0.07 |
Pb | — | — | — | — | — | 0.04 |
V | — | — | — | 0.012 | — | 0.15 |
Zn | 40 | 39 | 39 | 20.68 | 35.6 | 14.9 |
Comparison of metal concentrations levels in the homogenized egg
Metal | Moreiras et al. [ |
Fakayode and Olu-Owolabi [ |
Abduljaleel and Shuhaimi-Othman [ |
González-Weller et al. [ |
Iwegbue et al. [ |
This study (2015) |
---|---|---|---|---|---|---|
Al | — | — | 17.11 | 2.930 | — | 9.41 |
Ba | — | — | — | 0.468 | — | 0.72 |
Ca | 570 | — | — | — | — | 174 |
Cr | — | — | 3.24 | 0.115 | 0.32 | 0.17 |
Cu | — | 0.78 | — | — | 1.03 | 2.22 |
Fe | 19 | 23.20 | — | — | — | 5.49 |
K | 1300 | — | — | — | — | 491 |
Mg | 120 | — | — | — | — | 87.5 |
Na | 1400 | — | — | — | — | 1149 |
Ni | — | 0.03 | 1.11 | 0.038 | 0.86 | 0.05 |
Pb | — | 0.59 | 0.420 | — | 0.82 | 0.02 |
Sr | — | — | — | 0.388 | — | 2.05 |
Zn | 13 | 13.75 | 34.22 | — | 6.45 | 3.37 |
The macroelement concentrations obtained here in the different samples were lower (with the exception of Ca in the egg whites) than those recorded by the consulted authors. On the other hand, the concentrations obtained here for the trace elements were lower than those found by the authors (except Cu, Cr, Ba, Sr, Ni, and Al in homogenized egg samples).
Table
Comparison of metal concentrations in eggs from cage-reared hens.
Comparison of metal concentration levels in the egg whites
Metal | Giannenas et al. [ |
Alam Chowdhury et al. [ |
Demirulus [ |
This study (2015) |
---|---|---|---|---|
Cr | 0.048 | <LOQ | — | 0.02 |
Cu | 0.212 | 0.1 | 7.0 | 1.69 |
Fe | — | 2.96 | — | 1.46 |
Mg | — | 43.26 | — | 81.2 |
Ni | 0.064 | 12.81 | 3.7 | 0.03 |
Pb | — | 1.06 | — | 0.02 |
V | 0.013 | — | — | 0.12 |
Zn | 1.003 | 16.88 | 7.4 | 0.92 |
Comparison of metal concentration levels in the egg yolks
Metal | Giannenas et al. [ |
Alam Chowdhury et al. [ |
Demirulus [ |
This study (2015) |
---|---|---|---|---|
Cr | 0.066 | <LOQ | — | 0.12 |
Cu | 1.357 | 0.16 | 10.5 | 3.21 |
Fe | — | 27.27 | — | 18.6 |
Mg | — | 75.96 | — | 31.7 |
Mn | 0.836 | — | 1.9 | 0.36 |
Mo | 0.26 | — | — | 0.07 |
Ni | 0.063 | 2.79 | 1.7 | 0.07 |
V | 0.012 | — | — | 0.15 |
Zn | 20.68 | 81.97 | 35.6 | 14.9 |
Comparison of metal concentrations levels in the homogenized egg
Metal | González-Weller et al. [ |
Alam Chowdhury et al. [ |
This study (2015) |
---|---|---|---|
Al | 2.930 | — | 9.41 |
Ba | 0.468 | — | 0.72 |
Cr | 0.115 | <LOQ | 0.17 |
Cu | — | 0.26 | 2.22 |
Fe | — | 30.66 | 5.49 |
Mg | — | 119.22 | 87.5 |
Ni | 15.6 | 0.038 | 0.05 |
Pb | — | 1.06 | 0.02 |
Sr | 0.388 | — | 2.05 |
Zn | — | 98.85 | 3.37 |
The concentrations of Cu and V obtained by Demirulus [
As regards the metal content obtained in the yolk samples in the present research, the levels of Cu, Mn, Ni, and Zn obtained by Demirulus [
As for the metal content of the homogenized eggs, the concentrations of Fe, Mg, Pb, and Zn obtained by Alam Chowdhury et al. [
Consumption data, provided by the Spanish Agency for Food Safety and Nutrition (AESAN), has been used to evaluate the contribution to the daily intake for the metals studied which is 24.3 g/person/day for children aged between 7 and 12 and 31.2 g/person/day for adults over the age of 17 [
The daily requirements (recommended daily intake, RDI) for children and adults in the Spanish population have been established by Spanish Federation of Nutrition, Food and Dietetic Societies (FESNAD) and are as follows [ 1200–1500 mg Na/day for children (6–13 years) and 1500 mg/day for men and women 2000–3100 mg K/day for children (6–13 years) and 3100 mg/day for men and women 800–1100 mg Ca/day for children (6–13 years) and 900–1000 mg/day for men and women 170–280 mg Mg/day for children (6–13 years), 300 mg/day for women, and 350 mg/day for men 0.7–1.0 mg Cu/day for children (6–13 years) and 1.1 mg/day for men and women 9–12 mg Fe/day for children (6–13 years), 18 mg/day for women, and 9 mg/day for men 1.5–1.6 mg Mn/day for children (6–13 years), 1.8 mg Mn/day for women, and 2.3 mg/day for men. 6.5–8 mg Zn/day for children (6–13 years), 7 mg Zn/day for women, and 9.5 mg/day for men 15–21 mg Cr/day for children (6–13 years), 25 mg Cr/day for women, and 35 mg/day for men 22–34 mg Mo/day for children (6–13 years) and 45 mg/day for men and women. The tolerable daily intake (TDI) of nickel is 2.8 The tolerable weekly intake (TWI) of aluminium is 1 mg Al/kg bw/week [ The UL of vanadium is 1.8 mg V/day for adults (19–>70 years) [ The UL of boron is 3–6 mg/day for children (1–8 years) and 17–20 mg/day for adults (18–>70 years) [
Concerning the toxic metals, different values have been used. The European Food Safety Authority (EFSA) has established the following limits:
The Institute of Medicine, Food and Nutrition Board (IOM) set the following tolerable upper intake levels (ULs):
The Scientific Committee of Health and Environmental Risk (SCHER) established the TDI value of barium in 0.02 mg Ba/kg bw/day [
The World Health Organization (WHO) established a tolerable daily intake (TDI) of 0.13 mg Sr/kg bw/day for the Sr [
In the case of lead, the EFSA has calculated a BMDL01 whose values are 0.5
Taking into account the average consumption of the cage-reared hens’ eggs, the daily intake and their contribution to the RDI and to the TDI of the different studied metals have been estimated and the results are shown in Table
Estimation of the daily intake (mg/day) and contribution (%) to the recommended daily intake (RDI) of the essential metals analyzed.
Edible part |
EDI (mg/day) |
EDI (mg/day) |
% RDI | |||
---|---|---|---|---|---|---|
Men | Women | Children | ||||
|
||||||
Na | White | 26.5 | 34.1 | 2.27 | 2.27 | 1.77 |
Yolk | 7.46 | 9.58 | 0.64 | 0.64 | 0.50 | |
H | 27.9 | 35.9 | 2.39 | 2.39 | 1.86 | |
K | White | 13.2 | 16.9 | 0.55 | 0.55 | 0.42 |
Yolk | 15.3 | 19.6 | 0.63 | 0.63 | 0.49 | |
H | 11.9 | 15.3 | 0.49 | 0.49 | 0.39 | |
Ca | White | 1.90 | 2.44 | 0.24 | 0.24 | 0.17 |
Yolk | 18.8 | 24.2 | 2.42 | 2.42 | 1.71 | |
H | 4.23 | 5.43 | 0.54 | 0.54 | 0.39 | |
Mg | White | 1.97 | 2.53 | 0.72 | 0.85 | 0.71 |
Yolk | 0.77 | 0.99 | 0.28 | 0.33 | 0.28 | |
H | 2.13 | 2.73 | 0.78 | 0.91 | 0.76 | |
|
||||||
|
||||||
Cu | White | 0.04 | 0.05 | 4.79 | 4.79 | 4.10 |
Yolk | 0.08 | 0.10 | 9.11 | 9.11 | 7.80 | |
H | 0.05 | 0.07 | 6.31 | 6.31 | 5.40 | |
Fe | White | 0.04 | 0.05 | 0.51 | 0.25 | 0.30 |
Yolk | 0.45 | 0.58 | 6.46 | 3.23 | 3.77 | |
H | 0.13 | 0.17 | 1.90 | 0.952 | 1.11 | |
Mn | White | — | — | — | — | — |
Yolk | 0.01 | 0.01 | 0.48 | 0.62 | 0.54 | |
H |
|
|
0.14 | 0.18 | 0.16 | |
Zn | White | 0.02 | 0.03 | 0.30 | 0.41 | 0.28 |
Yolk | 0.36 | 0.46 | 4.87 | 6.62 | 4.51 | |
H | 0.08 | 0.11 | 1.11 | 1.50 | 1.02 | |
Cr | White |
|
|
0.002 | 0.002 | 0.002 |
Yolk |
|
|
0.001 | 0.02 | 0.01 | |
H |
|
|
0.02 | 0.02 | 0.02 | |
Mo | White | — | — | — | — | — |
Yolk |
|
|
0.01 | 0.01 | 0.004 | |
H |
|
|
0.001 | 0.001 | 0.001 |
Edible part |
EDI (mg/day) |
EDI (mg/day) |
% UL, PTWI, or TDI | ||
---|---|---|---|---|---|
Adults | Children | ||||
|
|||||
Al | White | 0.37 | 0.48 | 4.88 | 7.47 |
Yolk | 0.27 | 0.35 | 3.57 | 5.47 | |
H | 0.23 | 0.29 | 3.00 | 4.59 | |
Sr | White | 0.06 | 0.07 | 0.80 | 1.22 |
Yolk | 0.06 | 0.07 | 0.81 | 1.24 | |
H | 0.05 | 0.06 | 0.72 | 1.10 | |
V | White |
|
|
0.21 | 0.16 |
Yolk |
|
|
0.26 | 0.20 | |
H |
|
|
0.36 | 0.28 | |
B | White | 0.01 | 0.02 | 0.10 | 0.45 |
Yolk | 0.01 | 0.02 | 0.10 | 0.42 | |
H |
|
|
0.06 | 0.25 | |
Ba | White | 0.01 | 0.02 | 1.14 | 1.74 |
Yolk | 0.04 | 0.06 | 3.99 | 6.10 | |
H | 0.02 | 0.02 | 1.64 | 2.51 | |
Ni | White | 0.73 |
0.94 |
0.49 | 0.75 |
Yolk | 1.70 |
2.18 |
1.14 | 1.74 | |
H | 1.22 |
1.56 |
0.81 | 1.25 | |
Pb | White | 0.49 |
0.62 |
1.82 | 2.53 |
Yolk | 0.97 |
1.25 |
3.64 | 5.05 | |
H | 0.49 |
0.62 |
1.82 | 2.53 |
Egg yolks are, in general, the part that contributes most to the recommended daily intake of the essential metals, except for the contribution percentages for Na and Mg, which are higher in the homogenized egg. It was found that egg yolks have the highest contribution of Ca for adults (2.4%), whereas the homogenized egg provides the highest Na contribution for children (1.9%), followed by Mg and K.
Cu is the trace element that makes the highest contribution to daily intake (9.1% for adults, 7.8% for children), followed by Fe, Zn, and Mn. On the other hand, the contribution of Mo and Cr to the daily intake is low.
Regarding the toxic metals, the highest percentage contributions are found in the egg white for Al (4.88% adults, 7.47% children) and in the yolk for Ba (3.99% adults, 6.10% children) and for Pb (3.64% adults, 5.05% children). However, these contribution percentages do not pose a health risk.
Macroelement metals and trace metals have been determined in cage-reared hen’s eggs on the island of Tenerife (Canary Islands, Spain) by means of ICP-OES. This study shows that, in general, the yolk is the part of the egg that has the most metals, with significant differences in the levels of the metals studied with the other part of the egg. Eggs are an acceptable source of essential elements, in particular of Cu, Fe, and Zn. In addition, the consumption of eggs does not mean a high contribution of toxic metals.
The authors declare that there are no conflicts of interest regarding the publication of this paper.