Cereal Chem 58:367 - 370.  |  VIEW ARTICLE
Relation Between Phytic Acid and Trace Metals in Wheat Bran and Soybean.

R. Ellis and E. R. Morris. Copyright 1981 by the American Association of Cereal Chemists, Inc. 

Gel filtration chromatography of extracts of wheat bran suggests that at least 70% of the phytate of wheat bran does not occur as Ca5Mg-phytate. Apparently iron and zinc are the only soluble metals of wheat bran associated with phytate. No soluble zinc of soybean eluted with phytate, but 30 and 70% of the soluble iron of whole and defatted soybean, respectively, eluted in the phytate fraction. Low-phytate soybean was prepared by treating the finely ground whole soybean with a crude phytase enzyme (a cold water extract of wheat bran). This reduced the phytate-zinc molar ratio from 33 to 13. Rats were fed egg white-glucose diets without or with 12 ppm zinc as raw soybean, autoclaved soybean, low-phytate soybean, ZnSO4, or raw soybean plus ZnSO4. Four-week gains (in grams) were 5+/-4, 152+/-13, 182+/-12, 186+/-6, 185+/-14, and 198+/-11, respectively. Total femur zinc (in micrograms) was 20.8+/-1, 25.6+/-2, 39.8+/-3, 52.4+/-1, and 66.4+/-7, respectively. Although the soluble zinc of soybean apparently is not associated with phytate, reduction of phytate improved the bioavailability of the soybean zinc to rats.