Effects of boiling treatment upon the distributions of selenium and mercury in short-necked clam

In this paper, the effect of boiling treatment upon the distribution of selenium and mercury in the edible tissues of the short-necked clam Ruditapes philippinarum was investigated in relation with each elution profile of both elements to the cooking liquid (generally called "Kaijiru" in Japan). During the boiling treatments (5 min, 10 min, 20 min and 30 min at about 90 ﾟC), the variation of both levels were not apparently observed in the edible tissues, however, the level of dissolved selenium in the cooking liquid tended to increase slightly with time. The chemical species of the dissolved selenium was mainly organic. On the other hand, dissolved mercury was not detected from the fact that the mercury level was extremely low in the edible tissues. This suggested that a trace amount of Hg-Se complex as a final detoxified substance was not excreted out of body by means of the boiling treatment. The Se/Hg value (the molar ratio of selenium to mercury) in the edible tissues of the short-necked clam as an indicator of the safety of marine products was almost constant (about 100 1) through all boiling treatments, and then the safety of mercury in the edible tissue was confirmed against the boiling treatments.