Semolina extraction from wheat bran using an electro‐separation process

Abstract

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 electro-statically 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. Practical applications The wheat milling process in an industrial installation passes through several steps that are optimized to extract maximum semolina from grains. However, still a residual endosperm stays attached to the bran due to the process itself. Literature estimates wheat bran around 15% of the grain, which can be an important quantity taking into account the huge amount of cereal produced and consumed around the world. The suggested complementary process aims at the extraction of residual semolina attached to wheat bran through treating wheat bran by abrasion and later separate obtained components using and an electrostatic field. Obtained results, showed that treating wheat bran using the suggested method allows recovery of around 50% as semolina from the treated quantity. So, this reduces thrown wheat bran quantity to the half, which is important from an industrial point of view since it increases the production from the same wheat quantity.