Food Additives and Contaminants: Part BVol. 5, No. 4, December 2012, 268–271

Determination of trace elements in goat and ovine milk from Calabria (Italy) by ICP-AES

P. Licataa*, G. Di Bellab, A.G. Potortıb, V. Lo Turcob, A. Salvob and G.mo. Dugob

aDipartimento di Sanita Pubblica Veterinaria, Facolta di Medicina Veterinaria, Universita di Messina, Messina, Italy;bDipartimento di Scienze degli Alimenti e dell’Ambiente, Facolta di Scienze MM.FF.NN, Universita di Messina, Messina, Italy

(Final version received 19 June 2012)

There are many sources of contamination to which milk could be exposed: grazing animals can ingestcontaminants present in nature, such as lead in soil, or that have been deposited on grass, resulting fromindustrial emissions. Another possible route of contamination is represented by feed for animals, which maycontain heavy and essential metals. The potential of high-resolution inductively coupled plasma spectrometry wasevaluated to quantify reliably various toxic and essential elements (Fe, Zn, Pb, Cr, Ni, Cu, As, Se, Cd) in 47samples of goat and ovine milk from various farms in Calabria (southern Italy). The results showed thatconcentrations of cadmium were below the limit of detection. Lead levels were below the maximum limits as setby the EC in almost all samples tested. The highest values were those of Zn followed by Fe, Cu and Se.

Keywords: goat; ovine; milk; elemental analysis; ICP-AES

Introduction

Technological progress, various industrial activitiesand increased roadway traffic have caused a significantincrease in environmental contamination. The almostubiquitous presence of some metal pollutants, espe-cially Cd and Pb, facilitates their entry into the foodchain and thus increases the possibility of causing toxiceffects on humans and animals. However, agriculturalactivities can also be important sources of contamina-tion of the environment, of the food chain andeventually of food products consumed by humans(Balduini et al. 2000). Milk is a basic food in thehuman diet, both in its original form and as variousdairy products. As an excretion of the mammarygland, it can carry numerous xenobiotic substances(pesticides, drugs, metals, etc.), which constitute atechnological risk factor for dairy products, for therelated commercial image and, above all, for the healthof consumers (Naccari et al. 2006). Dairy ingestion offood contaminated with undesirable substances poses arisk for grazing animals as well as those confined.Heavy metals are undesirable substances in animal feedas this is the start of the chain of production for dairysheep. Milk and milk products contain a certainamount of metals that can be toxic and non-toxic.There are many sources of environmental contamina-tion to which milk is exposed. Grazing animals caningest it naturally, such as from the lead in soil or ongrass as deposited by industrial emissions. Another

possible route of contamination is through the feed foranimals, which may contain heavy as well as essentialmetals. The main elements that pose a danger to foodsecurity are arsenic, cadmium, lead and mercury,whose toxicity has long since been studied (Iaconoet al. 1992). Determination of heavy metal contami-nation in milk could be an important indication of thehygienic status, as well as an indirect indication ofthe degree of pollution of the environment in which themilk was produced (Gambelli et al. 1999; Imparatoet al. 1999).

Copper, manganese and zinc are important micro-nutrients in human and animal diet, as they areinvolved in many physiological processes. Manganesein particular plays an important role in the metabolismof proteins, carbohydrates, lipids and in the productionof steroidal sexual hormones; moreover, it is thecofactor of enzymes such as RNA synthetase, gluta-mine synthetase, pyruvate decarboxylase, manganesesuperoxide dismutase and arginase (Dugo et al. 2006).

Selenium is an essential nutrient for humans andanimals. It acts as a protective agent against heavymetal toxicity, cancer and cardiovascular diseases(Salonen et al. 1988; Anderson and Nielsen 1993).Regarding iron, salts are important for theirpro-oxidant properties. Although ferrous sulphatedemonstrates acceptable bioavailability, it has higherpro-oxidant properties than ferric glycinate, ferrousfumarate or ferrous succinate. However, ferric

*Corresponding author. Email: patrizia_licata@virgilio.it

ISSN 1939–3210 print/ISSN 1939–3229 online

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glycinate, iron (III)-EDTA and iron protein succinylatehave better bioavailability than ferrous sulphate. Inertiron compounds such as ferric pyrophosphate are verystable when added to foods, but these are poorlyabsorbed from the diet.

Materials and methods

Sampling

During April and May 2010, a total of 47 milk samplesfrom goat and ovine farms in Calabria, Southern Italy,were collected according to Italian procedures andnorms in order to minimise possible external contam-ination. Each milk sample comprised seven takings ofmilk during the morning milking in the same range ofthe day (between 8:00 a.m. and 10:00 p.m.). Thirty-seven samples were goat milk: 35 came from theprovince of Vibo Valentia and 2 from the province ofReggio Calabria. All 10 ovine milk samples came fromthe province of Vibo Valentia. The fresh milk sampleswere immediately placed in ice and afterwards frozenand stored at �20�C until analysis. The ovine werekept in free stalls and had heterogeneous characteris-tics of breed, age and weight. Sampling and storagesteps were optimised so as to reduce all possiblecontamination, loss or alteration that could negativelyaffect data reliability.

Trace elemental analysis

For practical reasons, all milk samples were firstlyophilised within the same storage containers. Thisgreatly facilitated subsequent digestion of organiccompounds while at the same time allowing dilutionto be minimised. The reagents and standards used werehigh purity for ICP analysis. Calibration curves wereconstructed from five dilutions out of 1 g/L standardsolutions. All glassware was cleaned before analysiswith 10% HNO3. Fe, Zn, Pb, Cr, Ni, Cu, As, Se andCd were determined by inductively coupled plasma–atomic emission spectroscopy (ICP-AES). Microwavemineralisation (FKV, Milestone Ethos, Bergamo,Italy) was applied to extract minerals. Of eachsample, 0.5 g was weighed in a vessel in TFM and7mL of 65% HNO3 and 1mL of 35% H2O2 wereadded. After the digestion program (microwave power1500W, 200�C), the vessels were opened and thesolutions were transferred to flasks and brought tovolume with ultrapure water. Elemental analysis wasperformed using a Horiba Jobin Yvon ICP-AES(Milan, Italy) with the torch positioned in radialmode. The plasma operated with a concentric nebulisercoupled to a cyclonic chamber with the followingexperimental conditions: 1.2 kW, argon flow 14L/min,auxiliary argon flow 1.0L/min and spray gas1mL/min. To achieve greater sensitivity, the

determination of As and Se was performed using ahydride generator, formed by reaction of sodium tetraborohydride (1% in 0.5M NaOH) in 6M hydrochloricacid. Table 1 shows the selected wavelengths, whichwere chosen so as to minimise interference, and Table 2the detection limits, calculated according to theEuropean Pharmacopoeia.

Analytical determinations

Quantitative analysis was performed using calibrationcurves (R24 0.995). For all elements, blank concen-trations were lower than the respective detection limits.Quality of the analytical data was checked by theanalysis of certified reference materials BCR-150 andBCR-151 (two different spiked skim milk powders;Nova Chimica, Cinisello Balsamo, Milan, Italy) andthe results were compared with certified values. Theanalytical conditions (LOD, precision and accuracy)for each element are reported in Table 2.

Results

The results of goat and ovine milk analysis, reported inTables 3 and 4, were compared with data reported in

Table 2. Analytical performance for each element analysed.

ElementLOD(mg/kg)

Precision (%)(RSD%, n¼ 10)

Accuracy(%)

Cd 30.3 6.5 91Cr 45.0 7.2 95Cu 15.1 4.5 98Fe 30.7 4.1 102Ni 7.5 6.7 97Pb 40.5 3.1 95Zn 55.0 4.2 104As 23.6 3.9 94Se 10.5 3.5 96Mn 30.0 4.1 95

Table 1. Analytical conditions for each element studied.

Element Wavelength (nm)

Cd 226.5–228.8Cr 205.5–267.7Cu 223.0–324.7Fe 234.3–240.5Ni 216.5–231.6Pb 220.3–405.8Zn 206.2–213.8As 189.0Se 196.0Mn 257.6–259.4

Food Additives and Contaminants: Part B 269

literature related to breast milk and cow’s milk. Theconcentrations of Fe in the tested samples were higherthan those found in breast and cow’s milk. Theconcentrations of Cu, Cr, Cd and As are similar tothose found in cow’s milk, whereas the levels of Ni arethe lowest in all samples. The concentrations of Zn arehigher than that of other metals determined in allsamples analysed. The results were compared with datain the literature related to breast milk and cow’s milk.However, the data show that among toxic metals, Cdwas found at levels below the instrumental detectionlimits. Concentrations of Pb were lower than the limitsof Decreto Legislativo (DL) No. 149 (2004) in almostall samples analysed, whereas for non-toxic metals thehighest values were for Zn followed by Fe, Cu and Se.

Discussion

The mineral composition of milk may vary dependingon the physiological condition of individual stages oflactation and/or environmental and dietary factors. InTables 5 and 6, some intake considerations on goat andovine milk are given, related to Recommended Daily

Allowance (RDA) values as defined by Pellett (1988).Comparison with literature data related to ovine andgoat milk has demonstrated that although today a limitis set for Pb, based on preliminary data obtained, it canbe assumed that the consumption of ovine and goatmilk can provide valuable content in the essentialelements important for various metabolic activities.The two different types of milk are comparablealthough the ovine milk has a higher content of zincand goat milk a higher content of copper.

This study demonstrates that in milk fromCalabria, highest concentrations are that of Zn fol-lowed by Fe, Cu and Se. From a more detailed analysisof the results obtained, it appears that the range of Zn(2.65–20.54mg/L) for goat milk and for ovine milk(10.35–25.65mg/L) were higher than that reported byliterature in bovine milk (Alais 2000; Simsek et al.2000). The low levels of As could be due to the fact thatno parasiticides and environmental disinfectants(arsenical compounds) are applied in the zones wherethe farms are located. Concentrations of Pb and Cd forgoat and ovine milk were lower than those reported inthe national and international literature (Cerutti 1999;Gambelli et al. 1999; Imparato et al. 1999; Alais 2000;Martino et al. 2001). Lead levels were lower than therange of values reported by Martino et al. (2001) incow milk samples and below DL No. 149 (2004) limitsin all samples studied, which is attributed to the factthat Calabria is a region with low industrial activities.As regards Cd, its presence was lower than instrumen-tal detection limits in all samples, which shows thereare no Cd-related toxicological risks in the Calabriaregion. Se levels were lower than those reported byother authors (Tiecco 2000; Martino et al. 2001). Asregards Cu values, it is important to underline that

Table 4. Concentrations of elements in samples of ovinemilk from Calabria.

ElementMean� SD(mg/kg)

Range(min–max)

% Positivesamples

Cd 5LOD – –Cr 0.06� 0.01 5LOD–0.08 6Cu 0.34� 0.10 5LOD–0.79 25Fe 3.29� 1.40 0.32–20.7 100Ni 0.06� 0.02 5LOD–0.16 56Pb 0.06� 0.02 5LOD–0.09 6Zn 16.23� 2.15 10.35–25.65 100As 0.24� 0.10 5LOD–0.43 12.5Se 0.07� 0.03 5LOD–0.15 25Mn 0.10� 0.08 0.04–0.26 100

Table 3. Concentrations of elements in samples of goat milkfrom Calabria.

ElementMean� SD(mg/kg)

Range(min–max)

% Positivesamples

Cd 5LOD – –Cr 5LOD – –Cu 0.71 5LOD–0.86 30Fe 2.82� 1.95 0.52–8.45 100Ni 0.04� 0.02 5LOD–0.08 80Pb 0.06� 0.02 5LOD–0.08 30Zn 11.31� 5.10 2.65–20.54 100As 0.16� 0.14 5LOD–0.34 30Se 0.11� 0.08 5LOD–0.19 20Mn 0.34� 0.15 0.20–0.40 100

Table 6. Nutritional consideration of ovine milk.

ElementRDA

(mg/day)Mean(mg/L)

RDA%(0.20L)

Cu 1 0.003 0.06Mn 2 0.001 0.01Se 0.055 0.0007 0.25Fe 14 0.033 0.05Cr 0.040 0.0006 0.3Zn 10 0.162 0.32

Table 5. Nutritional consideration of goat milk.

ElementRDA

(mg/day)Mean(mg/L)

RDA %(0.20L)

Cu 1 0.007 0.14Mn 2 0.003 0.03Se 0.055 0.001 0.36Fe 14 0.028 0.04Zn 10 0.113 0.22

270 P. Licata et al.

55% of all milk samples (goat and ovine milk) showedconcentrations lower than those found by otherauthors. This is most probably due to the Zn contentof feed, which interferes with the copper absorptionsystem in the animals, resulting in low levels of thismetal in milk samples (Balduini et al. 2000). Finally, asregards Cr concentrations, only 6% showed measur-able levels, whereas 94% presented values belowinstrumental detection limits for ovine milk samples.These findings are in line with those reported by otherauthors (Baldini et al. 1990; Cerutti 1999). At present,there are no specific maximum limits for heavy metalsin milk, except for Pb, where DL No. 149 (2004)establishes a limit of 0.02mg/kg w/w. Therefore, the Pbconcentrations as found below MLs in goat and ovinemilk samples in Calabria indicate that the milk is safefor the consumer. In general, low levels of heavy metalsare definitely related to the fact that the farms are alllaboured by families.

Conclusions

For greater food safety, it would be advisable toestablish MLs for various metals, not only for milk andother dairy products but for all foods. The presenteddata show that the Calabria region poses a very lowrisk of environmental pollution because of the shortageof industries and the traditional management of dairyfarms. In particular, the ovine and goat milk can beconsidered a good alternative to cow’s milk, not onlyfor the characteristic taste and identity of the productsbut also for some nutritional aspects.

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