Unravelling the bread-making functionality of gluten-rich sub-aleurone flour obtained by dry fractionation of wheat miller's bran

The residual endosperm of wheat miller's bran is rich in gluten proteins due to the presence of protein-rich sub-aleurone cells. Here, the goal was to gain insight into the bread-making functionality of sub-aleurone gluten-enriched fractions obtained through dry fractionation of miller's bran and the inherent bread-making functionality of sub-aleurone gluten. Therefore, two sub-aleurone gluten-enriched fractions (Sub-alF and Sub-alC), differing in particle size distribution and chemical composition, were prepared from miller's bran using impact milling, sieving, and air classification. Substituting 22.5% of white flour with Sub-alF, Sub-alC, commercial gluten A (GluA) and B (GluB), all standardised to a protein content of 20.6 % with wheat starch, led to an increase in specific loaf volume of 14.8%, 14.0%, 14.3%, and 21.8%, respectively. Despite their higher level of bran contamination and lower relative gluten content, Sub-alF and Sub-alC were equally functional as commercial gluten (GluA). This could be due to wet fractionation, which is used in commercial gluten production, reducing the functionality of gluten, as indicated by comparing the functionality of gluten in Sub-alC and gluten isolated via wet fractionation from Sub-alC with GluA. Substituting 6% of white flour with gluten isolated via wet fractionation from Sub-alC and from the corresponding flour increased the specific volume by 27.2% and 29.4%, respectively. Sub-aleurone gluten and flour gluten were, hence, functionally comparable. In conclusion, the sub-aleurone's high content of functional gluten enables the production of functional gluten-enriched ingredients from miller's bran.