Phytic acid content and "in vitro" iron, calcium and zinc bioavailability in bakery products: The effect of processing

Whole-grain bakery products and cereals are valuable sources of dietary fiber, vitamins, and trace elements. However, the presence of phytate, could decreases mineral bioavailability due to its chelating properties. In this study, the effect of fermentation and baking on the phytate content of different bakery products was measured by HPLC; the mineral availability in bakery products during processing was investigated by measuring solubility and dialysis, as well as the mineral uptake and transport by Caco-2 cells after in vitro digestion. Raw materials showed the highest amount of phytate, causing an important effect on the stage of processing. The solubility and dialyzability of iron increased with fermentation, meanwhile calcium and zinc showed a high variability depending on the product analyzed. After baking, the dialyzability of minerals increased with respect to the fermented dough in most cases. The highest uptake and transport efficiency of iron and calcium in cells corresponded to dough after fermentation of wheat flour with respect to the baked samples. For zinc, no differences were observed between fermented dough and after baking on uptake and transport efficiencies. This study showed that in vitro mineral availability of bakery products is influenced by the stage of processing and ingredients used. (C) 2011 Elsevier Ltd. All rights reserved.