Effects of the Fermented Soya-bean on Absorption of Zinc, Iron and Copper in Rats

Abstract

Effects of the removal of phytate from defatted soya-bean by fermentation on absorption of zinc, iron and copper were investigated. Rats were fed diets containing defatted soya-bean (DS) , fermented defatted-soya-bean (FDS) or fermented defatted-soya-bean added with phytate (FDS + phytate) for 19d. During the last 5 d, the apparent absorption of zinc, iron and copper were determined. At the end of the feeding trial, digesta in the upper and the lower half of the small intestine was separately collected to measure the solubility of minerals. Apparent absorption of zinc and copper were significantly (P<0.05) higher in rats fed the FDS than animals fed the DS. Furthermore, femoral zinc concentration was greater in the FDS group than the DS group. Surprisingly, apparent absorption of zinc and copper, and femoral zinc concentration were higher in rats fed the FDS+ phytate than rats fed the FDS. Solubility of zinc and iron were increased by feeding the FDS with or without phytate in both segments. We conclude that the fermentation of DS improves absorption of zinc and copper. Phytase in the FDS is suggested to be still active in the digestive tract and to degrade phytate in digesta. However, the disappearance of added phytate could not be enough to account for these results. The lower phosphorylated inositols in the FDS might improve mineral absorption.