In-vitro mineral binding capacity of five fiber sources and their insoluble components for magnesium and calcium

In-vitro binding of calcium (Ca) and magnesium (Mg) by total dietary fiber, hemicellulose A (HCL A), lignocellulose (LCL), cellulose (CL), and lignin (L) fractions isolated from rice bran (RE), wheat bran (WE), oat fiber (OF), apple fiber (AF) and tomato fiber (TF) was evaluated. At pH 6.8, significant amounts of Ca were bound by whole fibers, ranging from 800 mu g g(-1) for RE to 10 097 mu g g(-1) for TF. Mg bound by whole fibers varied from 496 mu g g(-1) for OF to 2177 mu g g(-1) for WE. Re-acid washing (pH < 2.0) released 95-99% of the Ca and Mg bound to the fibers. Fibers with the highest endogenous Ca and Mg concentrations bound significantly (P < 0.05) the highest amounts of the minerals studied. The Ca bound by HCL A varied from 9753 mu g g(-1) for RE to 11337 mg g(-1) for TF, whereas Mg bound varied from 1151 mu g g(-1) for OF to 5626 mu g g(-1) for TF hemicellulose fractions, respectively. Among the fiber components, Mg binding decreased in the order HCL A > LCL > L > CL, whereas Ca bound was in the order HCL A > LCL > CL > L. A relatively strong correlation was observed between the combined effects of protein content, hemicellulose, and lignin vs total Ca and Mg bound. (C) 1998 Elsevier Science Ltd. All rights reserved.