Abstract
Wheat bran consumption is associated with several health benefits, but its incorporation into food products remains low because of sensory and technofunctional issues. Besides, its full beneficial potential is probably not achieved because of its recalcitrant nature and inaccessible structure. Particle size reduction can affect both technofunctional and nutrition-related properties. Therefore, in this study, wet milling and cryogenic milling, two techniques that showed potential for extreme particle size reduction, were used. The effect of the milling techniques, performed on laboratory and large scale, was evaluated on the structure and physicochemical properties of wheat bran. With a median particle size (d50) of 6 µm, the smallest particle size was achieved with cryogenic milling on a laboratory scale. Cryogenic milling on a large scale and wet milling on laboratory and large scale resulted in a particle size reduction to a d50 of 28–38 µm. In the milled samples, the wheat bran structure was broken down, and almost all cells were opened. Wet milling on laboratory and large scale resulted in bran with a more porous structure, a larger surface area and a higher capacity for binding water compared to cryogenic milling on a large scale. The extensive particle size reduction by cryogenic milling on a laboratory scale resulted in wheat bran with the highest surface area and strong water retention capacity. Endogenous enzyme activity and mechanical breakdown during the different milling procedures resulted in different extents of breakdown of starch, sucrose, β-glucan, arabinoxylan and phytate. Therefore, the diverse impact of the milling techniques on the physicochemical properties of wheat bran could be used to target different technofunctional and health-related properties.
Highlights
Nowadays, there is an increasing demand from consumers for more healthy and qualitative food products, often with a focus on dietary fibre
The particle size of wheat bran was reduced with wet milling and cryogenic milling, both on laboratory and pilot scale
With wet milling on a laboratory scale, particle size reduction was slower, and the d50 only reached a plateau at 40 μm after 53 min of milling
Summary
There is an increasing demand from consumers for more healthy and qualitative food products, often with a focus on dietary fibre. Wheat (Triticum aestivum L.) bran, a by-product of the production process of white flour, is known to be a good source of dietary fibre and other bioactive components, like phytochemicals, vitamins and minerals. Foods 2020, 9, 1755 of the multilayered botanical bran structure consisting of a pericarp, testa and nucellar epidermis, together with the aleurone layer and remnants of the starchy endosperm [5]. The pericarp, the outer layer, is a rigid structure mainly consisting of empty cells made up of mostly arabinoxylan (AX), cellulose and lignin. The cubic shaped aleurone layer is characterised by the highest concentration of bioactive compounds, minerals and vitamins [6]
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