Phytase activity and degradation of phytic acid during rye bread making

Summary in the original language of the document

Changes in phytic acid content, activity of phytase and α-amylase in rye breads were determined during rye bread making.
The activity of phytase is highest in grain and flour whereas the activity in the sourdoughs is almost the half of the activity in the flour. The activity was unchanged in the dough after mixing and proofing.
Degradation of phytic acid (IP6) into lower inositol-phosphates and free phosphate is almost completed during the production of rye bread with long fermentation time whereas the degradation is less completed when whole grains are included in the recipe. In rye bread made from milled rye (DB00), 99% of IP6 is degraded and IP3 becomes the dominating inositol-phosphate in this bread type presumably resulting in a high level of bioavailable minerals. In rye bread made with 30% grains (SB30), 94% of the IP6 content was reduced with IP4 and IP3 being the dominating lower inositol-phosphates. In rye bread made with 50% whole grains (KB50) the degradation of IP6 was 82%, and the three inositol-phosphates IP5, IP4 and IP3 were found in equal amount in this bread type. Due to significant amounts of phytic acid and remaining IP5, some of the minerals might not be available for human absorption after consumption of this bread type.