In vitro binding capacity of wheat bran, rice bran, and oat fiber for Ca, Mg, Cu, and Zn alone and in different combinations

Wheat bran (WB), rice bran (RB), and oat fiber (OF) were analyzed for their proximate constituents and mineral content and evaluated for their binding capacity for calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn). Protein, soluble and insoluble dietary fiber, and endogenous mineral contents varied significantly among the three dietary fiber sources. With the exception of Mg, in higher concentration in RB, WB contained significantly (P < 0.05) more endogenous Ca, Cu, and Zn than RB or OF. Overall, WB bound significantly more Ca and Mg (alone or combined with other minerals) than RB and OF, respectively. OF bound more Cu than RB or WB. Zn (alone or in the presence of other minerals) was bound more strongly in WB and RB than OF. Re-acid washing stripped most of the bound minerals from the dietary fiber sources.