Pesticide Residues in Milk and Milk Products - Pesticides: Evaluation of Environmental Pollution - page 579

milk compared to the levels in raw milk (Liaska 1968). Endosulfan sulfate found in spray-
dried, evaporated, and roller-dried milk showed around 42%, 42%, and 70% decrease com-
pared to raw milk, whereas concentration decrease of chlordane for these products was
approximately 25.0%, 45%, and 50%, respectively (Liaska 1968). The skimming of cow's
and buffalo's milk led to a slight reduction in the pesticide (β-BHC, lindane, DDT) residue
concentration (Liaska 1968).
Preparation of butter from churning buffalo's or cow's cream reduced the concentration
of HCB, lindane, Aldrin, heptachlor epoxide, chlordane, and total DDT. This might be due
to the transfer of most of the fat globules to the butter milk carrying considerable pesticide
residues (Langlois et al. 1974; Waliszewski et al. 1997).
In cheese-making, heating and salting caused a great amount of degradation of lepto-
phos residues. The reduction in total DDT in Ras cheese, made from contaminated raw
milk spiked at different levels (0.1, 1, and 10 ppm), was 40.6, 33.9, and 25.5%, respectively,
at the end of a 6-month storage. This reduction was effected by Streptococci, Lactobacilli,
and yeasts. The reduction of lindane was higher in Domiati cheese made by acid-enzyme
coagulation than Ras cheese made by enzyme coagulation. The reduction of pesticides
in cheese may be due to the microorganisms in ripening cheese as well as interference of
pesticide residues with cellular metabolism of the microorganism (Chacko and Lackwood
1967; Hantke and Bradley 1972; Kim et al. 1970).
The manufacture of yoghurt from buffalo's or cow's milk resulted in the decrease of
levels of pesticide residues. This reduction might be due to heat treatment as well as the
activity of the starter culture.
18.6 Maximum Residual Limits
Maximum Residual limits (MRLs) for various pesticide residues have been fixed by differ-
ent International and National Regulatory bodies (Table 18.2).
18.7 Quantification of Pesticide Residues in Milk and Milk Products
Pesticide analysis plays an important role in estimating human and environmental expo-
sure to various compounds in diverse agricultural practices. Since the analyte concentra-
tions are generally very low and the sample matrix is complex, the interference of matrix
should be considered when performing a measurement. So, the analysis of the sample
requires studious sample preparation steps, extraction methods, and cleanup steps to
minimize the interfering of the matrix. The analysis of pesticide residues in milk and milk
products involves the following steps:
1. Sample preparation
2. Extraction
3. Cleanup or isolation
4. Separation and detection.