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

Previous studies have shown that baking alters the digestibility of gluten. This study compared the structure and in vitro digestibility of gluten within dough and bread, baked at either 230 °C or 150 °C for 25, 35 or 45 min. Protein digestion was investigated using mass spectrometry, specifically by calculating the accurate concentration and defining the release profile of six immunogenic gluten peptides that are involved in celiac disease activation. The release profile of these peptides in the intestinal phase differed between dough and bread; multiple peptides, including the immunodominant 33mer, were present at higher concentrations earlier in dough digesta suggesting raw gluten may exhibit and higher-gluten load and different immunogenicity profile. • Gluten protein structure and digestibility were examined within a bread system. • Mass spectrometry was used to track the release of immunogenic celiac peptides. • Baking temperature and time increased the degree of gluten polymer aggregation. • The baking temperature and time did not alter the peptide release profile. • Peptide release differed between dough and bread suggesting altered immunogenicity. 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. [ABSTRACT FROM AUTHOR]