Behaviour and fate of polychlorinated biphenyls during processing of some dairy products

This study was conducted to elucidate the behaviour of milk contaminants polychlorinated biphenyls (PCBs 28, 52, 101, 138 and 180) during manufacturing processes for cheese, yoghurt and fatty products compared with the corresponding raw milk. The evaluation was carried out using gas chromatography coupled with mass spectrometry (GC-MS). In soft cheese, PCB congener 138 showed the highest level, followed by PCB 180 and PCB 153. Also total PCBs decreased gradually until the end of the ripening period. In yoghurt, the influence of storage period on the percentage reduction in total PCBs was 13.79% after 5 days and 24.78% after 10 days. Some congeners are degraded by microbial processes, PCBs 180, 28 and 101 being reduced by about 55.6, 19.7 and 13%, respectively. Wide variations in congener concentrations in raw milk were reflected by their percentage contributions in fatty products. Congeners PCB 138, 153 and 180 were the most abundant in all fatty product samples.