Triboelectric separation of wheat bran tissues: Influence of tribo‐material, water content, and particle size

Abstract

AbstractThe separation behaviors of wheat bran tissues with different water content and particle sizes were investigated after tribocharging with three kinds of organic polymers to clarify the effects of tribo‐material and particle property on triboelectric separation (TES). The surface composition of wheat bran tissues was also analyzed in situ by Raman micro‐spectroscopy to confirm their triboelectric series. The results showed the tribo‐materials could reverse the separation behaviors of wheat bran tissues. Due to differences in charge amounts, aleurone and intermediate layer (IL) particles showed the similar separation behaviors contrasting that of the outer pericarp. On the basis of the separation behaviors and the results of surface composition analysis, a triboelectric series of wheat bran tissues could be deduced as follows: (+) starch > polyamide > aleurone > IL > outer pericarp > polyethylene > PTFE (−). Moreover, drying of bran particles could improve the separation selectivity and effectivity of TES, but decreasing the particle size of bran tissues merely increase the yields of the enriched fraction obtained by TES.Practical ApplicationsTriboelectric separation (TES) is a green and sustainable dry fractionation for enriching nutritional cereal products, such as wheat aleurone, protein, and glucans. However, a suitable mechanism to improve its efficiency by choosing the tribo‐material and processing wheat bran particles before TES remains unclear. In this study, the separation behaviors and triboelectric series of wheat bran tissues were obtained to guide the selection of tribo‐materials for cereal products. Also, the separation feasibility of a cereal product by TES can be estimated based on the surface composition analyzed by situ Raman micro‐spectroscopy. The results about the pretreatment of starting material, including optimizing of water content and particle size, can contribute to the application of TES in separating cereal and food products.