Gluten degradation in wheat flour with Aspergillus niger prolyl-endopeptidase to prepare a gluten-reduced bread supplemented with an amaranth blend

• The AnPEP wheat flour effectively reduces gluten immune-reactivity.
• The modified bread (AnPEP wheat flour with amaranth) has acceptable quality.
• Modified bread has 99% less immune-reactive gluten than conventional wheat bread.

Celiac disease and other-gluten related disorders are characterized by an inadequate immune reaction against dietary gluten. Some strategies have been developed for gluten modification, to reduce or avoid the immune response. The aim of this study was to modify gluten proteins in wheat flour using the Aspergillus niger prolyl-endopeptidase (AnPEP) to elaborate bread supplemented with amaranth blends, evaluating its immunoreactivity and technological quality. The reaction conditions: enzyme (dilutions 1:50, 1:100 and 1:500), temperature (35 or 40 °C), substrate (WF) (10% or 20%, w/v), time (1–8 h), gluten content by R5-ELISA, and the protein composition by SE-HPLC were analyzed. For bread-making, 60% of modified WF and 40% of amaranth blends (20:80, 30:70, 40:60; raw: popped, respectively), and two fermentation times (52 and 90 min) were tested. Specific volume and gluten content were evaluated. The best reaction conditions were (1:50) AnPEP, 20% WF, and 8 h incubation at 35 °C. The bread supplemented with the 20:80 amaranth blend showed a higher specific volume and after a 52 min fermentation had 99% less immunogenic gluten than the wheat bread. The use of the amaranth blend in combination with WF modified by AnPEP is an effective way to obtain gluten-reduced breads with acceptable quality.