Isolating a fraction enriched in sub-aleurone gluten proteins through dry fractionation of wheat miller's bran

Abstract

Wheat's sub-aleurone is rich in gluten but mainly ends up in the miller's bran fraction during milling. Here, the goal was to investigate dry processing to fractionate miller's bran into a functional fraction enriched in sub-aleurone gluten proteins and hence gain fundamental insight into the behaviour of miller's bran and sub-aleurone during dry processing. Impact milling and sieving of miller's bran yielded a sub-aleurone-enriched fraction (27.4% mass yield, 22.4% protein, 63.2% starch) and starchy endosperm-poor fraction enriched in dietary fibre (62.6% mass yield; 27.4% arabinoxylan). The ash and phytate contents of the sub-aleurone-enriched fraction are higher than those of the corresponding flour because of (limited) aleurone cell opening during the impact milling. Subsequent pin disc milling, and air classification of the sub-aleurone-enriched fraction resulted in a sub-aleurone gluten-enriched fraction. This fraction had a protein content of 31.4%, an absolute gluten content of 24.5% and lower arabinoxylan content per unit protein than flour.

Industrial relevance

The production of a sub-aleurone-enriched fraction through impact milling and sieving of miller's bran presents an opportunity to increase the flour yield in industrial mills. Additionally, the sub-aleurone gluten-enriched fraction offers a promising alternative to commercial gluten. Nowadays, commercial gluten is manufactured through energy-intensive wet processing methods. Furthermore, also the starchy endosperm-poor fraction could serve as an ingredient enriched in dietary fibre. In conclusion, this study contributes to increasing resource efficiency in the wheat manufacturing industry by repurposing a by-product of wheat milling.