Arabinoxylans concentrates from wheat bran by electrostatic separation

Abstract

Electrostatic separation has been recently proposed as a novel method to fractionate wheat bran into valuable ingredient fractions. However, systematic study into the influence of parameters on electrostatic separation was lacking. Therefore, this study aimed at a more detailed evaluation of electrostatic separation for enriching arabinoxylans (AX) from wheat bran. The influence of wheat bran particle size, carrier gas velocity and charging tube length were investigated with a lab-scale electrostatic separator. A combination of larger particle size (D[4,3] of 210μm compared to 110μm), higher gas velocity (>28m/s) and shorter charging tube (125mm compared to 225mm) can sufficiently charge the particles, and at the mean time avoid agglomeration by oppositely charged particles. With the optimal settings, single step electrostatic separation of wheat bran could increase the AX content from 23% dm to 30% dm, which is similar as can be obtained by sieving. However, in comparison to sieving, the yield of the enriched fraction from electrostatic separation is lower due to the horizontal design of the setup. Improvement of the yield is expected when adjusting the system design from horizontal to vertical. A sieving step added after the electrostatic separation could effectively remove starch and protein and resulted in a fraction with an AX content of 43% dm, which is around the theoretical maximum value that can be reached by dry fractionation.