Sampling
Raw milk samples of cows were collected from a cow farm during the morning milking directly into sterile screw-topped bottles (500 ml), to avoid potential contamination due to metallic containers and collected tanks (n = 60). About 60 composite milk samples were collected from five different milk shops on monthly basis in 2006, located in different sites of Hyderabad city, Pakistan. The milk samples were collected in pre-washed plastic bottles (250 mL in capacity) from the bulk tank on each shop and immediately placed in an ice box. The six different processed milk samples, packed on different dates (10 samples of each brand) were purchased from the local market. On arrival the laboratory, the milk samples were stored at −20 °C till further analysis. Three replicate determinations were carried out on each sample. Thus, a total of 60 × 3 = 180 milk samples of each collected from farm, shops and processed, were analyzed.