The influence of some technological procedures, such as heat treatment of wheat-flour (thermal processing), the temperature and the period of dough’s fermentation, the addition of phytase to the dough so as to decompose phytic acids, as well as the degree of freeing calcium and iron from the bread, has been described. The research carried out by the Institute of Biotechnology in Warsaw concerned the wheat-bread’s dough with calcium carbonate and the 10% addition of fibers from the spent grain. The content of phytic acids and thus the degree of their decomposition were determined by HPLC. The content of calcium and iron in the bread was described by flame atomic absorption spectroscopy (FAAS), and the content of calcium and iron available- by the method of enzymatic in vitro digestion. It was found that the bread made of wheat-flour, which had been treated by the heat, had a lower content of phytic acids than that made of wheat-flour that hadn’t been treated by the heat, which pointed to a partial decomposition of phytic compounds in flour under the influence of the elevated temperature. Elevating the fermentation’s temperature from 15 and 20 to 30°C caused a clear increase in phytic acids’ hydrolysis degree, which also lowered considerably their concentration, especially in the bread made of flour which had been previously exposed to the heat treatment. This indicates that in a higher temperature phytase is more active and also the degree of phytic acids’ decomposition is higher. Increasing the fermentation’s time from 0,5 h to 3 h in 30°C lowered considerably the content of phytic acids in the obtained bread (about 12% lower without heat treatment and about 24% after it). However, increasing the fermentation’s time from 3 h to 16 h caused only insignificant lowering of these acids. The addition of phytase to the dough that had been fermenting for 0,5 h influenced a considerable, 55% decrease in phytic acids’ content in the bread, compared with the variant without phytase. In case of bread with the addition of phytase, made of flour that had been treated by the heat, this decrease was slightly bigger (58%). Increasing the fermentation’s time from 0,5 h to 3 h in 30°C caused a significant, 70% decomposition of phytic acids in the obtained bread. The addition of phytase and prolonging the time of dough’s fermentation influenced a 11% increase in the calcium and a 78% increase in the iron availability.