Extrusion-Cooking Modifies Physicochemical and Nutrition-Related Properties of Wheat Bran

Abstract

The potential of extrusion-cooking to change the physicochemical characteristics of wheat bran, increase its nutritional value and decrease its recalcitrance towards fermentation was investigated in this study. The conditions in a twin-screw extruder were varied by changing screw configuration, moisture content and barrel temperature. The former was not previously investigated in studies on bran extrusion. Extrusion-cooking resulted in an increased water-holding capacity and extract viscosity of bran, suggesting shear-induced structure degradation and structure loosening due to steam explosion at the extruder outlet. Modelling showed that the extent of these modifications mainly correlates with the amount of specific mechanical energy (SME) input, which increases with an increasing number of work sections in the screw configuration and a decreasing moisture content and barrel temperature. Extrusion led to solubilisation of arabinoxylan and ferulic acid. Moreover, it led to starch melting and phytate degradation. Upon fermentation of the most modified sample using a human faecal inoculum, small numeric pH decreases and short-chain fatty acid production increases were observed compared to the control bran, while protein fermentation was decreased. Overall, extrusion-cooking can improve the nutrition-related properties of wheat bran, making it an interesting technique for the modification of bran before further use or consumption as an extruded end product.

Optimisation of the Extrusion Process through a Response Surface Methodology for Improvement of the Physical Properties and Nutritional Components of Whole Black-Grained Wheat Flour

“…The WAI and the fracturability of the extrudates were increased by increasing the barrel temperature (T1–T3) and decreased with further increases in the barrel temperature (T3–T5), whereas the hardness showed the opposite trend ( Table 4 ). The increase in the WSI of the extrudates with increasing barrel temperature was attributed to the increase in soluble components with starch melting by extrusion [ 53 , 54 ]. The results were in agreement with those reported by Ding et al [ 47 ], who stated that a higher zone-5 barrel temperature may increase the degree of wheat starch gelatinisation, thereby lowering the WAI and increasing the WSI of the extrudates.…”

“…Chen et al [ 18 ] reported phenolic acids (except for gallic acid) and flavonoid of Jizi439 black wheat bran were significantly increased by optimizing the extrusion and extraction condition. This result may be attributed to the destruction of anti-Fe and Cu nutritional factors of wheat by extrusion [ 54 ]. Native starch content is altered due to the applied temperature and presence of water content during extrusion.…”

Advances on the Valorisation and Functionalization of By-Products and Wastes from Cereal-Based Processing Industry

“…Such an effect is likely to be owing to the high shear-stress forces and high temperatures applied that can cause the release of ferulic acid, softening of lignin and AXs depolymerization. In other studies it was demonstrated that modification of extrusion conditions resulted in an increase in the WEAX and ferulic acid yields from corn and wheat bran [90,91].…”

Changing Wheat Bran Structural Properties by Extrusion-Cooking on a Pilot and Industrial Scale: A Comparative Study

“…In such a context, it is desirable to apply modification techniques that increase the interaction of bran with water, open aleurone cells, degrade phytate and increase the bran soluble dietary fibre content. Potential techniques include particle size reduction, bioprocessing and extrusion-cooking [ 12 , 13 , 14 ].…”

“…It results in the solubilisation of AX, the opening of aleurone cells, degradation of phytate and release of ferulic acid. In previous studies, the extent of the effects was shown to depend on the applied process parameters such as moisture contents, set temperature, screw speed and configuration design [ 14 , 15 , 16 , 17 , 18 , 19 ]. However, the extrusion-cooking experiments described in these studies were performed on different extruder sizes going from a lab-scale extruder with a feed rate of 1.3 to 3 kg/h [ 16 , 17 ] to a BC45 extruder with a feed rate of 20–32 kg/h [ 15 ], making comparison difficult.…”