Influence of microbial conversion and change in pH on iron–gallic acid complexation during lactobacillus fermentation.

Abstract: Plant products are rich in minerals, e.g. iron, as well as in phenolic acids, e.g. gallic acid (GA). GA contains a galloyl group leading to complexation with iron, and thus decreasing the bioavailability of iron. As complexation of GA–iron seems to be pH-dependent, lactic acid fermentation could be a technique to improve the bioavailability of iron. On the other hand different lactobacillus strains are able to metabolize GA into pyrogallol (PYR). In this study, the influence of pH and microbial conversion of GA on iron complexation during fermentation with Lactobacillus plantarum and Lactobacillus collinoides was investigated. PYR was detected as the only conversion product of GA. At the end of the fermentations, a decreased pH to 5 and 5.7 for L. plantarum and L. collinoides respectively was measured. Based on the colour change during fermentation and based on the spectrophotometric analysis with standards, complexation between iron and GA or PYR was established. From the results, it could be concluded that the effect of pH on complexation was more pronounced compared to the microbial conversion of GA. Based on these results, L. plantarum is an efficient bacteria to destabilize the formed complexes which could lead to an improved bioavailability of iron. [Copyright &y& Elsevier]