Seasonal Evaluation of Mineral Elements, Heavy Metals, Essential Amino Acids, Proximate Compositions and Pesticides in Goat Milk

Abstract

Samples of goat milk were collected from different locations of Kano state in wet and dry seasons. The samples were analysed for mineral elements, heavy metals, essential amino acids, proximate compositions and persistent organic pollutants using standard methods of chemical analysis. The flame atomic absorption spectrometry (FAAS) results indicated that the mean concentrations of calcium and magnesium in the samples are 329±15.66 mg/kg and 118±8.75 mg/kg respectively. These values are above the National Environmental Standards Regulations Enforcement Agency (NESREA) set values for food, drug and beverages. The mean concentrations of zinc, copper and nickel in the samples were 2.01±0.29, 0.69±0.02 and 0.89±0.12 mg/kg respectively. These values were slightly above the standard. The mean levels of lead, cadmium and chromium in the samples were 0.02±0.003, 0.02±0.004 and 0.01±0.003 mg/kg respectively. This implies that the samples were rich in mineral elements and essential metals and safe from toxic metals contaminations. The chromatographic analysis for essential amino acids in the samples revealed high concentrations of lysine, histidine, threonine, valine, methionine, leucine, isoleucine and phenylalanine of 7.58, 2.78, 4.22, 5.23, 3.31, 6.99, 9.04 and 4.00 in g/100 g protein respectively compared to Food and Agriculture Organization (FAO) and World Health Organization (WHO) standards values. The Pearson correlation coefficient analysis was performed using MATLAB student version IV software, the results indicated strong and moderate positive correlations between mineral elements and essential amino acids while weak and low correlations were observed between essential metals and toxic metals, this showed the strong metal binding property between the amino acids, mineral elements and essential heavy metals, all the values were determined at significant level of P≥0.05. The gas chromatography-mass spectrometry analysis of the organochlorine pesticides in the samples indicated that the level of pesticides were below the detection limit (BDL) for both seasons. This indicated that the samples of this study were free from the pesticides contamination; this could be attributed to restriction and compliance for the usage or the economy because most of these pesticides are very expensive.