Electrostatic Basis for Separation of Wheat Bran Tissues

New fractionation technologies are presently under investigation in order to enhance the wheat bran nutrient value. The explicit aim of this paper is to evaluate the possibility of using electric field forces for the separation of the fine particles generated from each wheat bran tissue during the milling process. Corona-charging and surface-potential-decay experiments were performed on samples of finely ground wheat bran and aleurone tissues (maximum size of 0.3 mm). Ground bran, which has a higher moisture content, more rapidly loses the charge imparted by corona discharge. For both kinds of samples, finer particles charged better than larger particles, and lyophilized samples were found to better preserve their charge than those not subjected to a freeze-drying process. An experiment carried out using a belt-type corona electrostatic separator validated the possibility of sorting these tissues based on the differences in their charge decay characteristics. Tribocharging experiments performed on the same tissues have also led to encouraging results: The charge/mass ratio of ground bran tissues was twice that of aleurone. These differences in the physical properties of the two types of tissues provide the technical basis for the development of electrostatic-separation technologies as part of more efficient bran-cracking strategies.