Milling and fermentation influence mineral and phytic acid retention in zinc-biofortified wheat

Abstract

Wheat biofortification is an effective strategy to reduce micronutrient deficiencies. High retention and bioavailability of these micronutrients during processing is crucial. This study aimed to evaluate the effects of flour extraction rate and food processing on Zn, Fe, and phytic acid (PA) concentrations and indicators of potential mineral bioavailability in 60 Zn-biofortified wheat lines milled at 100%, 85% and 70% extraction rates (ER) and transformed into pan-bread and chapati. Reducing flour extraction rate from 100% to 70% decreased Zn, Fe, and phytic acid concentrations by approximately 70% (49.14 to 14.69 mg/kg), 49% (34.24 to 17.34 mg/kg), and 79% (0.97 to 0.20 g/100 g), respectively. Chapati and pan-bread production did not negatively impact Zn and Fe concentrations; however, PA content declined during processing, with greater reductions observed during pan-bread production due to PA degradation during fermentation. Pan-bread also showed lower phytate molar ratios, indicating improved potential mineral availability. The potential nutritional contribution of these products was evaluated in the context of Pakistan, where wheat is a major dietary staple and average wheat consumption is approximately 280 g/day. Based on this consumption level and theoretical Zn absorption estimates derived from the PA molar ratio, pan-bread produced from 100% ER flour was estimated to provide up to 149% of the physiological Zn requirement for women, while chapati produced from 85% ER flour was estimated to provide 95%.These results indicate that maintaining relatively high flour extraction rates can preserve Zn and Fe, while fermentation can reduce phytic acid and improve indicators of potential mineral availability, highlighting the importance of processing practices for maximizing the nutritional benefits of Zn-biofortified wheat in wheat-dependent populations such as Pakistan.