Transfer of chemical elements from milk to dairy products

A pilot study was carried out to evaluate the transfer of As, Cd, Pb, Ni, Cr and Hg from milk to dairy products and to correlate their behavior with that of some components and macro-elements of milk. Due to the low level of these chemical elements in most common commercial products, hard cheese was produced starting from cow's milk spiked with the analytes of interest. Several intermediate and final products coming from cheese making were sampled and analysed for content of fat, dry matter, proteins, macro and oligo-elements. The relationship between spiked elements and milk components was evaluated through both the study of concentration factors and the statistical analysis (Principal Component Analysis and correlation matrix). Except for As and Hg, a clear correlation between spiked elements and milk components was found so a likely bond with proteins, fat and dry matter was demonstrated. As for Pb, for which a legal limit (Maximum Level, ML) is set in the pertinent European regulations, it was found that the link with proteins could lead to an increase of this element concentration different from the mere concentration factor from milk to cheese. Furthermore, it was proven that the stage of ripening affected the variation of Pb concentration so this aspect should be deeply considered in case of setting a ML in cheese or extrapolating a ML from milk to cheese.