CONCENTRATION OF SELECTED ELEMENTS IN RAW AND ULTRA HEAT TREATED COW MILK

Journal of Microbiology, Biotechnology and Food Sciences Lukáčová et al. 2012 : 2 (2) 795-802 REGULAR ARTICLE CONCENTRATION OF SELECTED ELEMENTS IN RAW AND ULTRA HEAT TREATED COW MILK Lukáčová Anetta*1, Massányi Peter 2, Greń Agnieszka 3, Golian Jozef 1 Address: 1Slovak University of Agriculture, Faculty of Biotechnology and Food Sciences, Department of Food Hygiene and Safety, Tr. A. Hlinku 2, 949 76 Nitra, Slovak Republic 2 Slovak University of Agriculture, Faculty of Biotechnology and Food Sciences, Department of Animal Physiology, Tr. A. Hlinku 2, 949 76 Nitra, Slovak Republic 3 Pedagogical University, Department of Animal Physiology and Toxicology, ul. Podbrzezie 3, 31-054 Kraków, Poland * Corresponding author: ABSTRACT The potential presence of toxic metals in food is being recognized as a priority by standards organizations and constitutes an analytical challenge. The toxic metal content of milk and dairy products is due to several factors: environmental conditions, the manufacturing process and the possible contamination during several steps of the manufacturing processes. The aim of this study was to evaluate samples of raw milk with fat contents 3.8% obtained at randomly from animal farms in around Nitra, western Slovakia region and ultra – heat treated cow milk (UHT) with fat contents 1.5% commercially available from local market in Nitra. Samples of milk were analysed for metal contents using atomic absorption spectrophotometry (AAS). UHT milk showed higher levels of cadmium, nickel and iron. Higher levels of zinc, copper were detected in raw milk. Significant differences in the concentration of copper between raw and UHT cow milk were found. Keywords: metals, raw milk, ultra – heat treated cow milk 795 JMBFS / Lukáčová et al. 2012 : 2 (2) 795-802 INTRODUCTION Milk is considered as a nearly complete food since it is a good source for protein, fat and major minerals (Enb et al., 2009). Milk is an important source of all basic nutrients required for mammals including human beings. Milk from various mammals such as cow, buffalo, goat, sheep is used for different nutritional purposes, e.g. feeding to young ones and preparation of some nutritional products such as milk cream, butter, yogurt, sour milk, etc. (Hassan, 2005). The major chemical components of milk include water, fats, proteins, carbohydrates, minerals, organic acids, enzymes and vitamins (Dobrzanski et. al, 2005). Milk and milk products are the most diversified of the natural foodstuffs in terms of composition, contains more than twenty different trace elements (Stawarz et al., 2007). Most of them are essential and very important such as copper, zinc, manganese and iron. These metals are cofactors in many enzymes and play an important role in many physiological functions of man and animals (Koh and Judson, 1986). Increasing industrialization has been accompanied throughout the world by the new distribution of mineral substances from their natural deposit. Many of these have undergone chemical changes and finally pass, finely dispersed and in solutions, by way effluent sewage, dumps and dust, into the water, earth and the air and thus into the food chain (Florea et al., 2006). Contamination of food products by heavy metals is becoming an unavoidable problem. These agents have led to metal dispersion in the environment and consequently, impaired health of the population by the ingestion of victuals contaminated by harmful elements (Žukowska et al., 2008). The amount of metals in uncontaminated milk is admittedly minute, but their contents may be significantly altered through manufacturing and packaging process as well as metals that may contaminate feed and environment such as cadmium, chromium, nickel and cobalt could be excreted into milk at various levels and causing serious problems (Schuhmacher et al., 1991). Toxicity of metal is closely related to age, sex, route of exposure, level of intake, solubility, metal oxidation state, retention percentage, duration of exposure, frequency of intake, absorption rate and mechanisms/efficiency of excretion (Mertz, 1986). Those metals described as “heavy metals” which, in their standard state, have a specific gravity of more than about 5 g.cm-3. Some of them, such as cooper, nickel, 796 JMBFS / Lukáčová et al. 2012 : 2 (2) 795-802 manganese, chromium and iron are essential in very low concentration for the survival of all forms of life (Watson, 2001). Only when they are presented in higher quantities, can these, like the heavy metals lead, cadmium be toxic also in very low concentrations and cause metabolic anomalies (Hernandez-Avila et al., 2003). Here, the boundary between the essential and toxic effects is somewhat problematic (Thomas, 2006). According to the Order of the Ministry of Agriculture of Romania, the maximal admitted for contaminating heavy metals in milk and cheese, are: 0.05 mg/kg for cadmium and 0.05 for mercury (the cadmium and the mercury are indexed only in case of meat and of marine animals meant for human consumption) (Florea et al., 2006) The aim of this study was to evaluate concentrations of selected metals in raw and ultra – heat treated cow milk and based on the results to determine the dependence between analyzed metals. MATERIAL AND METHODS Materials Samples (n=30) of raw and ultra – heat treated cow milk (UHT) were collected. The samples of raw milk with fat contents 3.8% were obtained random by from animal farms in region Nitra, western Slovakia. The samples of UHT cow milk with fat contents 1.5% commercially available were purchased from local market in Nitra. The samples were collected during the period from 2011 to 2012. Methods of Analysis Analysis involved the digestion of 1 g of samples with 20 mL of Analar grade HClO4 and HNO3 in proportion 4:1 which was be carried using validate methods of analysis. Samples were mixed at temperature of 120°C for about 65 min, cooled and transferred into 25 mL standard flask and filled to the final volume with deionised water. The content of the following elements (cadmium, zinc, nickel, iron and copper) were measured with voltammetric method (Stawarz et al. 2007). Metals were extracted from the milk according to AOAC method. The metals were measured by atomic absorption spectrophotometry (AAS). Maximum absorbance was 797 JMBFS / Lukáčová et al. 2012 : 2 (2) 795-802 obtained by adjusting the cathode lamp at specific slit and wave lengths. Fe was measured at 248.3 nm, Cu at 324.8 nm, Zn at 319.9 nm, Cd at 228.8 nm, Ni at 232.0 nm. The obtained results were expressed in mg.kg-1. Statistical analysis Basic variation statistical values (arithmetic mean, standard deviation, coefficient of variation, maximum and minimum value) were calculated. The significant differences between means were calculated by a one-way analysis of variance using Duncan´s multiplerange test at P<0.05 and correlation assay. RESULTS Result of element concentration in raw milk samples c (...truncated)