Effects of pH on the in Vitro Sorption of Mutagens to Dietary Fibers

Dietary fibers, alginate and defatted corn fiber, sorbed food mutagens, Trp-P-1 and Glu-P-1, which are heterocyclic amines formed in the cooking process. The sorption behavior of the heterocyclic amines to defatted corn fiber and alginates was analyzed under pH-controlled conditions. Glu-P-1 and alginic acid had pKa values of 4.2 and 3.6, respectively, whereas Trp-P-1, which showed alkaline in solution, possessed two pKa values of 4.8 and 7.7. Defatted corn fiber, which was mainly composed of cellulose and hemicellulose, did not show a significant pKa value. The amount of sorbed Trp-P-1 to the alginates increased as the pH value of the buffer was elevated, and was much more than that sorbed to defatted corn fiber at each pH condition. These results suggest that the alginates held the amino group of Trp-P-1 or Glu-P-1 on their carboxyl group as a cation exchanger.