Cereal Chem 61:357 - 359.  |  VIEW ARTICLE
Minerals and Phytate in the Analysis of Dietary Fiber from Cereals. II.

W. Frolich, T. F. Schweizer, and N.-G. Asp. Copyright 1984 by the American Association of Cereal Chemists, Inc. 

Dietary fiber and especially soluble fiber components in a wheat bread dough with a high content of fiber were associated with considerable amounts of ash when assayed with an enzymatic gravimetric method, using ethanol precipitation to recover soluble fiber. Only a small amount of minerals occurred in the insoluble fiber fraction, except for iron, 40% of which was associated with this fraction. Only a fraction of the minerals and phytate associated with the alcohol-precipitated soluble fiber could be removed by dialyzing the redissolved fiber. Soluble fiber dialyzed without previous alcohol precipitation contained much smaller amounts of minerals, but nearly 30% of the iron was bound to the soluble fraction also when prepared without ethanol precipitation. This study shows that the isolation procedure of fiber components heavily modifies their mineral-binding capacity. However, the different cations investigated (Ca, Mg, Fe, and Zn) were not uniformly affected by the isolation procedures. Great care is needed when extrapolating from in vitro studies with isolated fiber components to the native dietary fiber or to its effect in vivo.