Abstract
Extrusion-cooking can be used to change the techno–functional and nutrition-related properties of wheat bran. In this study, pilot-scale (BC21) and industrial-scale (BC45) twin-screw extrusion-cooking using different types of extrusion (single-pass, double-pass and acid extrusion-cooking) and process parameters (temperature, moisture) were compared for their impact on wheat bran. When applying the same process settings, the higher strong water-binding capacity, extract viscosity and extractability displayed by bran extruded using the industrial set-up reflected a more considerable wheat bran structure degradation compared to pilot-scale extrusion-cooking. This was attributed to the overall higher specific mechanical energy (SME), pressure and product temperature that were reached inside the industrial extruder. When changing the type of extrusion-cooking from single-pass to double-pass and acid extrusion-cooking, wheat bran physicochemical characteristics evolved in the same direction, irrespective of extruder scale. The differences in bran characteristics were, however, smaller on industrial-scale. Results show that the differentiating power of the latter can be increased by decreasing the moisture content and increasing product temperature, beyond what is possible in the pilot-scale extruder. This was confirmed by using a BC72 industrial-scale extruder at low moisture content. In conclusion, the extruder scale mainly determines the SME that can be reached and determines the potential to modify wheat bran.
Highlights
Wheat (Triticum aestivum L.) bran is a byproduct of the grain roller-milling process and is mostly used as an animal feed ingredient
We investigated the scale-up of wheat bran extrusion-cooking and its effects on bran properties, by going from a BC21 extruder to a BC45 extruder and to a BC72 extruder
Extrusion-cooking has considerable industrial potential as it can be executed on a large scale, is a cost-effective continuous short-time process and leads to the stabilisation of the final product
Summary
Wheat (Triticum aestivum L.) bran is a byproduct of the grain roller-milling process and is mostly used as an animal feed ingredient. It consists of botanical bran, aleurone and some residual endosperm. Wheat bran is a concentrated source of dietary fibre, mostly arabinoxylan (AX), as well as vitamins, minerals and other bioactive compounds. The consumption of wheat bran is linked to different positive health effects. The physical presence of the bran in the colon and the water-binding by the cell wall matrices and the capillary structures in wheat bran [1,2] can lead to an increased faecal bulk and normalised transit time [3]. Fermentation of dietary fibre by colon bacteria is another major mechanism by which bran mediates health [4]. The produced short-chain fatty acids (SCFA) can result in improved gut health and can influence metabolic health [5]
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