Abstract
The effect of dietary sodium phytate on the solubility of P, Ca, Mg and Zn in a purified diet based on casein-corn starch was investigated under various pH conditions. Both phytate-free and phytatecontaining diets were homogenized with 12 kinds of buffer solution of pH 1-12 and centrifuged 10, 000 ×g for 30min to separate the soluble (supernatant) and insoluble (residue) fractions. The ratio of insoluble mineral was expressed as a percertage of the insoluble mineral content relative to the total (soluble+insoluble) mineral content. Higher ratios of insoluble P in the phytate-containing diet than in the phytate-free diet were obtained at all values of pH examined. In pH values over 5, increased ratios of insoluble Ca exceeding 85% of total Ca were observed in both diets. No obvious Ca-precipitating effect of dietary phytate was recognized. On the other hand, dietary phytate did affect both Mg and Zn solubility. An appreciable increase in the ratio of insoluble Mg in the phytate-containing diet compared with the phytate-free diet was shown as the pH increased from 6 to 12. At about pH 7, the ratio of insoluble Zn in the phytate-free and phytate-containing diets was 25 and 60%, respectively. These ratios were lower than those in the content of the lower part of the small intestine of rats which were fed the same diets as those used in this experiment.
