Fermentation of soybean flour with Aspergillus usamii improves availabilities of zinc and iron in rats

Soybean flour was fermented with Aspergillus usamii to improve the availabi lities of dietary zinc and iron through the degradation of phytate. Three k inds of experimental diets that differed in protein sources were prepared: one consisting of 40% regular soybean flour (RS diet), one consisting of 40 % fermented soybean flour (FS diet), and one consisting of 20% regular soyb ean flour and 20% fermented soybean flour (RF diet). Zinc solubilities in t he upper and the lower segments of the small intestine were higher in rats fed the FS diet than in rats fed the RS diet. The FS group showed higher so lubility of iron in the lower small intestine than the RS group did. Zinc c oncentrations in the femur and plasma and iron concentrations in the liver and plasma were higher in the FS group than in the RS group. These results suggested that the fermentation of soybean flour improved the availabilitie s of dietary zinc and iron, which may be induced by increasing the solubili ties of these minerals in the small intestine through the reduction of phyt ate content. Femoral and plasma zinc concentrations in the RF group were hi gher than in the RS group, but lower than in the FS group. No difference wa s noted in liver and plasma iron concentrations between the RF group and th e FS group. Although phytase activity in FS degrades phytate in the RF diet , higher activity may be needed to degrade phytate completely.