Availability to the Chick of Zinc· Phytate Complexes Isolated from Oil Seed Meals by an in vitro Digestion Method

Studies were made of the form in which zinc was found after digestion in vitro of oil seed meals which varied in zinc availability in vivo. Regardless of in vivo differences, the zinc of two sesame meals and one safflower meal was present in an insoluble, nondialyzable Ca·Mg·Zn·phytate complex at intestinal pH. The zinc was little available to the chick as shown by low uptake of 65Zn from the labeled complexes. For a soybean meal digest, about 75% of the extracted zinc, 40% of the phytate phosphorus and 90% of the calcium and magnesium were soluble at intestinal pH. About 50% of the zinc was dialyzable in a 4-hour period. The zinc of the soybean meal digest was bound in a water-soluble and dialyzable complex which was more stable than zinc phytate. The binding agent was termed a “carrier.” The addition of soluble digestion products of the sesame or safflower meals to the insoluble labeled Ca·Mg·65Zn·phytate complexes did not promote dialysis of 65Zn, but the “carrier” rendered 15 to 29% of the 65Zn dialyzable at intestinal pH. Three isolated soy proteins contained low or no “carrier” properties.