Semolina extraction from wheat bran using an electro-­ separation­process

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The present paper is aimed at studying the improvement of the semolina extraction from durum wheat grains through a recycling of wheat bran, as a by-product, issued from traditional milling and sieving. Abrasion of the wheat bran and then electrostatically separating obtained components allowed a recovery of a significant amount of semolina, reaching 50% of the treated mass. Three components were obtained after separation, namely, semolina, fine bran, and relatively big bran. The electrostatic characterization, including surface potential decay and charge measurement, showed a clear conductive character with a slight difference between components in terms of charge conservation. This electric conductive behavior of the wheat bran leads to choose an induction-type electrostatic separator to extract residual semolina from the grinding process. The design of experiments methodology was used to study the influence of the main parameters: the applied high voltage, the conveyor speed, and the speed of the rotating part. The process was optimized taking into consideration both the quantity and quality of the recovered semolina, targeting a high recovery rate with the best possible quality. The physical and chemical analysis showed a good quality of the recovered semolina with 1.1% ash content.