Abstract
Effective conditions were investigated to remove residual cadmium from rice by treatment with surfactants. Neither fat fraction nor carbohydrate fraction of polished rice contained any significant amount of cadmium. It was found that cadmium occurred mostly in the protein fraction in a chelating state. Both cadmium and protein were efficiently removed from the polished rice when this was treated with each of sodium alkylbenzenesulfonate and sodium alkenylsulfonate. In each case there was a correlation between cadmium and protein in regard to the efficiency of removal. The difference in the alkyl group of the surfactant did not affect the efficiency for removing cadmium and protein. It was considered that each sulfonate-type surfactant had an interaction with the rice protein during washing to form a protein-surfactant complex containing cadmium and, as a result, cadmium was removed along with such a complex. This cadmium-containing complex was found to be formed most favorablly in the pH range of 7-9.
