Estimated Zinc Bioavailability in Milling Fractions of Biofortified Wheat Grains and in Flours of Different Extraction Rates

Abstract

In present study, control and Zn-biofortified grains were milled to estimate Zn bioavailability in various grain milling fractions and flours of various extraction rates. In all tissues of wheat grains, soil Zn application increased Zn concentration and bioavailability, while decreased phytate concentration and (phytate):(Zn) ratio. Compared with control grains, trivariate model of Zn absorption based estimated Zn bioavailability in various flour fractions of biofortified grains was greater by 50% or more. On average, bran had higher concentration of Zn and phytate as compared to whole grain and other milling fractions. Therefore, a large decrease was observed in concentration and estimated bioavailability of Zn from both control and biofortified wheat flour at lower flour extraction rates (80 and 65% extraction) when compared to flour of 100% extraction rate. Compared with four commercial wheat flours of similar flour extraction rate (80%), Zn bioavailability was significantly lower in flour from the control grains, while significantly greater in flour from the biofortified grains. Conclusively, only biofortified whole grain flour can ensure optimum Zn bioavailability (≈3 mg Zn per 300 g flour) for the human population groups reliant on wheat grains