Effects of processing and storage of dairy products on lindane residues and metabolites

Residue levels of lindane and its metabolites were monitored in 25 samples of raw and sterilized milk, yoghurt, Domiati & Ras cheese collected from different regions in the Great Cairo Governorates. The concentrations of lindane followed the order: raw milk > Domiati cheese > sterilized milk > yoghurt=Ras cheese. Most samples were found to contain three or more metabolites at different levels. Heat treatments (pasteurization, boiling and sterilization) reduced lindane levels. The reduction percentages were 65.0–73.0, 75.0–85.4, and 84.4% for lindane content and 0.1–43.0, 37.3–55.4, and 76.6% for total of lindane and its metabolites on pasteurization, boiling, and sterilization, respectively. A gradual reduction of lindane ranging from 1.4–8.9% was observed during the manufacture and storage of yoghurt for three days in a refrigerator. The reduction of lindane was higher in Domiati cheese made by acid-enzyme coagulation than that made by enzyme coagulation. On the other hand, the manufacturing process of Ras cheese removed 36.7% lindane after storage (ripening) periods of 6 months. This may be due to the effect of microorganisms during storage.