(17a) Selective Enrichment of Oat Groats Using Chemical-Free Electrostatic Separation

Traditional wet fractionation techniques utilize plenty amount of chemicals, extreme pH change and drying which lead to plant protein denaturation and loss of native functionality. In addition, during these processes energy and water are inefficiently consumed. The combination of sieving and tribo-electrostatic separation techniques was proposed by our research team as an effective and eco-friendly replacement of conventional oat protein fractionation methods. First, six sieves with different mesh sizes were tested. It was found that the coarse fractions were extracted from bran layer and the fine fractions were derived from the starch endosperm. Sieve aperture size of 106 µm was selected due its favorable size for fluidization. At this mesh size, the starch-rich fraction with 10.1% protein and the bran-rich fraction with 17.1% protein were obtained. This starch-rich fraction was further enriched by tribo-electrostatic separation consisting of fluidized bed vessel, tribo-charging tube, separation chamber equipped with one negative electrode and one positive electrode, air cylinder and high voltage supply. First, oat flour particles are tribo-charged in the charging tube where protein particles acquired a net positive charge before being separated in the fractionation chamber under external electric field. The impact of air flow rate and plate voltage on the separation performances were investigated. Relatively high protein enrichment and separation efficiencies were obtained at laminar air flow regime and high plate voltages of ~12kV. Additionally, second-stage electrostatic separation was conducted, and the protein content of the fraction collected from the negatively-charged electrode was increased to ~20%, equivalent to protein separation efficiency of ~35%. Our novel approach not only resulted in rapid simultaneous separation of protein and starch particles, but also preserved native bio-functionality of the separated proteins.