SELENIUM CONTENT OF SHEEPS MILK AND ITS DISTRIBUTION IN PROTEIN-FRACTIONS

The selenium (Se) distribution in sheep's milk is reported. Skim milk was found to contain the major part (98%) of total milk Se. The Se dis tribution over casein and whey protein fractions depends on the separa tion method used, but irrespective of these methods, skim milk Se is m ainly associated with the casein fraction (>68%). Approximately 11%, 4 % and 17% Se is removed by dialysis (molecular mass cut-off 10-12 kDa) from skim milk, casein and whey respectively, indicating a major asso ciation of Se with milk proteins. This observation is confirmed throug h Se analysis of individual caseins and whey proteins isolated through ion-exchange chromatography and gel filtration. Se concentrations of the different isolated milk proteins show considerable variations (cas eins, 304-750 ng Se/g; whey proteins, 241-806 ng Se/g).