DISTRIBUTION OF ADDED LEAD AND CADMIUM IN HUMAN AND BOVINE-MILK

Distribution of added lead and cadmium to bovine and human milk and wh ey has been studied. In bovine milk, about 97 and 89% of lead and cadm ium, respectively, were recovered in the casein fraction obtained by e nzymatic coagulation. However, only 6% of lead and 41% of cadmium were found in the same fraction separated by acid precipitation, indicatin g that the distribution of both metals is very different depending on the method used for milk fractionation. Moreover, gel filtration of bo vine and human skimmed milk and whey after addition of lead and cadmiu m was carried out. Most of the lead was associated to the casein fract ion after gel filtration of skimmed milk, whereas in the chromatograph y of whey, lead was eluted with the low molecular weight fraction in b oth species. However, a different pattern in the distribution of cadmi um has been observed in the two species studied. In contrast to the bi nding of cadmium to the low molecular weight fraction in human skimmed milk and whey, it was mainly associated to a component of a molecular weight around 70,000 in bovine skimmed milk. This component was not p resent in bovine whey indicating that it is separated with casein duri ng fractionation.