Iodine content in raw milk

The paper presents the latest information on iodine content in raw milk, in the Czech Republic. In 2005, iodine was determined using the Sandell-Kolthoff method in 169 milk samples, taken from transportation tanks (capacity 11 000–13 000 litres) of collecting milk for dairy processing, from 14 areas of South-western Bohemia. The average iodine content in milk samples was 442.5 ± 185.6 μg/l, minimum and maximum value were 68.6 and 1 000.6 μg/l respectively. 81.7% of the samples contained more than 250 μg/l. The average iodine content in milk from the collecting areas ranged from 230.2 ± 133.0 μg/l to 702.7 ± 166.2 μg/l (P < 0.001). In five collecting areas (i.e. 35.7%), means were higher than 500 μg/l. These values document the continuing trend of an increase in iodine content in raw cow’s milk, as well as permanent local and regional differences. Higher mean values were determined in the period of winter feed rations (April 495.9 ± 50.8 and October 494.3 ± 176.4 μg/l), while lower values were measured during the period of summer feed rations (September 350.9 ± 178.4 μg I/l) (P < 0.01). If converted per dry matter, 1 kg of dry milk matter contained, on average, 3.428 ± 1.497 mg iodine, maximum and minimum values were 0.543 and 7.995 mg respectively.