Chromium, copper, iron, manganese, selenium and zinc levels in dairy products: in vitro study of absorbable fractions.

Because milk and dairy products are some of the most widespread foods in the human diet, they contribute a large fraction of mineral intake. We determined levels of chromium, copper, iron, manganese, selenium and zinc in 60 samples of 10 widely consumed dairy products. Graphite furnace atomic absorption spectrometry was used to analyze samples processed with a slurry procedure to minimize sample pretreatment. The accuracy and precision of our method were verified. In analyzed samples, mean values ranged from not detectable to 0.950 microgram/g for Cr, from 0.020 to 2.800 micrograms/g for Cu, from 0.750 to 20.0 micrograms/g for Fe, from 0.010 to 0.900 microgram/g for Mn, from not detectable to 0.140 microgram/g for Se, and from 0.250 to 4.500 micrograms/g for Zn. The highest levels of Cr, Cu, Fe, Mn and Zn were detected in children's milk. Increased concentrations of Cr, Cu, Fe and Mn were detected in products packaged in glazed ceramic containers. We also studied the absorbable fractions of these elements using in vitro techniques which simulate human gastric and intestinal digestion.