Chemical forms of iron in commercial soy sauce and the soy sauce fortified with iron salts

Abstract

Chemical forms of iron were examined in commercial soy sauce and the soy sauce fortified with iron salts. Commercial soy sauce contained 10–46 p.p.m. of iron. The content depended on the kinds of soy sauce. The iron was soluble and most of it was in the ferrous state. Soy sauce had reducing activity, so that the ferric iron in soy sauce fortified with ferric iron salts was converted to ferrous iron. Ferrous iron was stable in soy sauce during the storage at 50°C for 40 days. Iron fortification of soy sauce at the level of 250 p.p.m. produced the undesirable changes in colour and flavour.