Influence of different types of protein on in vitro availability of intrinsic and extrinsic iron and zinc

The influence of beef, pork and soy proteins on intrinsic and extrinsic iron and zinc in vitro availability was investigated, by measuring mineral dialysability. Intrinsic iron dialysability (percentage of iron dialysed) was similar in the animal proteins and higher than that from soy protein isolate (P<0·001). Intrinsic zinc dialysability from pork protein was statistically (P<0·001) higher than that from other proteins studied. Beef and soy proteins do not differ in their percentages of zinc availability. The effect on the extrinsic iron availability was different among the three proteins studied, but not on the extrinsic zinc availability. The composition of amino acids and/or the small peptides produced during the digestion process of the protein can modify the iron, and probably the zinc, availability. The inorganic zinc addition (10 μg ml⁻¹) reduced the non-haem and extrinsic iron availability, while it did not affect the haem iron availability. At the concentrations used in this study (10 μg ml⁻¹) a decrease of zinc dialysability caused by the inorganic iron addition was not observed. ©1997 SCI