Chemical-Free Electrostatic Separation As a Dry Approach for Enrichment of Plant Proteins

Processing of plant-based resources and fractionation of their major components (protein and starch) still relies on wet conventional technologies that involve the use of solvents, concentrated acids and alkali through a series of operations that include aqueous extraction, heating, centrifugation, isoelectric precipitation, and energy-intensive dehydration step. These harsh processing conditions result in protein denaturation by reducing the quality, solubility and functionality of the protein components. We have developed a dry tribo-electrostatic separation approach for producing protein-rich fractions from different agricultural flours including oat, yellow pea and navy bean flours. Our process consisted of a fluidized bed, polytetrafluoroethylene (PTFE) tribo-charging tube, and a rectangular separation chamber supplied with two electrode plates made of copper. For this approach, the milled flour particles were initially suspended in the fluidized bed before being passed through the PTFE tribo-charging tube. The milled flour particles were then charged in contact with the PTFE media, according to their charging behavior. Protein particles are characterized by high ionizability, and they can be charged upon physical contact with the tribo-charging media. However, starch particles are characterized by low ionizability, thus, they cannot be charged effectively using triboelectricity. The charged protein particles were finally separated from uncharged starch granules in the rectangular chamber under the influence of an applied electric field. The influence of process parameters including air/nitrogen flow rate, tribo-charger tube length and plate voltage on the protein enrichment level was evaluated. Using this approach, the protein content of the original flours were increased by at least 50% in the final protein-rich fractions collected from the electrode plates. This proposed process provides an efficient, inexpensive, and environmentally friendly alternative to conventional protein separation processes in a chemical-free environment. The approach also preserves the native functionality of the proteins and eliminates the costly treatment of proteinaceous effluent released as a by-product stream during wet processes.