Fate of Organochlorine Pesticides During Processing of Milk into Dairy Products

Abstract

Abstract Two lactating dairy cows per group were fed selected pesticides dissolved in organic solvents and mixed into a grain concentrate for a two week period. The reference pesticides used in this study were dieldrin; a mixture of heptachlor, DDT, and lindane; toxaphene; chlordane; endosulfan (Thiodan); and dicofol (Kelthane). The milk from these contaminated cows was collected and processed into the following dairy products: pasteurized whole milk, 30% cream, butter, spray-dried whole milk, condensed whole milk, sterilized condensed whole milk, and Cheddar cheese. The byproducts (skim milk, buttermilk, and Cheddar cheese whey) from manufacturing these products were also saved for subsequent analysis. The residues in these dairy products and byproducts were extracted, cleaned up, and analyzed by electron capture gas chromatography. The 30% cream, condensed milk, and pasteurized milk were analyzed at 0, 7, and 14 days and Cheddar cheese, spray-dried milk, butter, and sterilized condensed milk after storage for 0, 3, and 6 months. The results indicated that, in general, the pesticides used were very stable for ordinary dairy processing operations and remained essentially unchanged even after storage at refrigeration and room tempera-tures for 6 months. However, dieldrin, lindane, and chlordane showed a 27, 34, and 11% decrease, respectively, for spray-dried products and the concentration of dicofol showed a slight decrease in the sterilized condensed whole milk products, whereas the concentration of DDE extracted from the products stored 3 and 6 months was generally less than the amount extracted initially. In manufacturing Cheddar cheese, most of the pesticides showed some bacteriostatic or bactericidal action against starter microorganisms. Generally the pesticide residues were found in greater concentration (on a fat basis) in the skim milk, buttermilk, and whey than in products from which these were derived. This might be attributable to the affinity of the residues for the lipoprotein portion of the products. Concentrations of dieldrin and toxaphene increased slightly during storage of the milk and milk products, suggesting that a reorientation occurred.