The effect of baking time and temperature on gluten protein structure and celiac peptide digestibility

Previous work has shown that baking induces structural changes within the gluten macropolymer (GMP) that reduce gluten protein digestibility. The precise nature of these structural changes within dough/bread, and how they alter the in vitro release profile of immunogenic gluten peptides that activate celiac disease is unknown. This work examined the effect of dough baking temperature and duration on the GMP's structure and the release profile of immunogenic gluten peptides. Dough was baked at either 150 °C or 230 °C for 25, 35 or 45 min. The structure of the GMP within the resulting loaves was defined and compared using confocal microscopy, quantitative protein network analysis, gliadin protein extractability (HPLC) and determination of the free thiol content. Both bread and dough were digested in vitro (INFOGEST) and the release profile of six immunogenic gluten peptides (including the immunodominant 33mer) defined using quantitative mass spectrometry. Higher baking temperatures and longer durations increased the degree of intermolecular disulfide bonds between the sulfur-rich gliadins and GMP backbone. The thermal load did not alter the GMP macrostructure, but significant differences between bread and dough were observed. Baking altered the concentration and release profile of the immunogenic gluten peptides throughout in vitro digestion causing the digestion of immunogenic gluten peptides differed between raw and heat-treated bread.