Investigation of the effect of black tea acidulation with citric acid or its natural source on dietary iron bioaccessibility

Despite the established inhibitory action of tea polyphenols on dietary iron absorption, the consumption of tea at mealtimes remains common in many regions of the globe where anaemia is still a public health concern. The objective of this study was to investigate the effect of acidulating black tea with citric acid or lime juice on dietary iron bioaccessibility. Firstly, the effect of citric acid on iron- polyphenol complex formation and iron speciation was studied using molecular spectrophotometry. Then, the bioaccessibility of dietary iron from pearl millet ball in the presence of black tea acidulated with citric acid or lime juice was assessed through a simulated in vitro digestion. Finally, the different species of bioaccessible iron were quantified. Citric acid reduced the absorbance of iron-polyphenol complex by 58.06% and 59.52% at pH 5 and 7, respectively, while promoting the formation of organic iron at pH 5 and ferrous iron at pH 5 and 7. Dietary iron bioaccessibility increased in the presence of acidulated black teas, with the greatest variation (28.57%) being observed in the digest of pearl millet ball mixed with lime juice-acidulated black tea. The more abundant bioacessible iron species was organic iron, and ferrous iron was more concentrated in digests of pearl millet ball mixed with lime juice-acidulated black tea. Acidulation of tea beverage with lime juice is a culinary technique that could mitigate the inhibitory action of tea polyphenols on dietary iron absorption and alleviate iron deficiency in populations consuming tea at mealtimes.