Comparative Study of Zinc, Manganese and Calcium in Commercially Available Milk Samples

Aim of the present study is to determine the concentration of metals, namely Zn, Mn, and Ca in different dry and liquid milk samples. All samples were collected in October 2014 from different markets of Karachi, Pakistan. Microwave digestion system was used for mineralization of samples. Zn and Mn were analyzed by flame atomic absorption spectrometry and Ca was analyzed by volumetric method of complexometric titration. The concentration of Zn, Mn and Ca in liquid milk samples were found to be (1.96 ? 3.640), (0.37 ? 0.52) and (195 ? 1528) ppm respectively while in dry milk samples (23.22 ? 30.5137), (7.67 ? 11.6) and (328 ? 336) ppm respectively. In liquid milk samples, the highest concentration of Zn, Mn and Ca were found in WM2 (3.64 ppm), WM6 (0.52 ppm) and WM2 (1528 ppm) respectively. In dry milk samples, the highest concentration of Zn, Mn and Ca were found in DM3 (30.5137 ± 0.0057) ppm, DM4 (11.6 ppm) and DM2 (336 ppm) respectively. The results of milk samples were compared to the limits, set by International Dairy Federation. Quality of liquid and dry milk samples according to International Dairy Federation was also determined. Concentration of Zn in most of the liquid milk sample was in agreement and some were below to the value set by International Dairy Federation. However, in dry milk, all samples exceeded the limit. Value of Mn in liquid as well as in dry milk samples exceeded the recommended value. Furthermore, value of Ca in dry milk samples was below to the limit, on contrary value was within the limit in some of the liquid milk samples while in others, value exceeded the recommended limit. The study showed that there is wide variation in the concentration of Zn, Mn and Ca between liquid milk samples and dry milk samples. Some of milk samples exceeded the permissible limits. So it is suggested that the concerned authorities should check and improve the level of these essential metals in milk available in markets.