(206c) Sustainable Fractionation of Plant-Derived Proteins with Pneumatic Tribo-Electrostatic Separation

The potential of a dry fractionation approach for the production of native plant protein concentrates has been validated for navy bean (Phaseolus vulgaris) flour as a model system utilizing a lab-scale pneumatic tribo-electrostatic separator. This methodology employed a tribo-electrostatic approach to selectively charge proteins, carbohydrates, and fibers in the bean flour and separate them based on the magnitude and type of their charge. For this approach, a wide variety of tribo-charging tubes with different sizes, shapes, and materials were screened to determine the most effective for use in tribocharging of the bean flour. The optimized process consisted of a fluidized bed flour reservoir, polytetrafluoroethylene (PTFE) tribo-charging tube, and a plate-type separation chamber. The location and distribution of the charged protein-rich particles along the surface of the electrode plate was investigated as a function of air flow rate (laminar vs. turbulent) and electric field strength. Protein-rich fractions were collected from bottom, middle and top sections of the electrode plate and analyzed for protein content and particle size distribution. Particles were imaged using scanning electron microscopy (SEM). A turbulent air flow rate at a variety of electric field strengths resulted in the formation of protein-rich particles and starch granule agglomerates affecting the production of high-purity protein concentrates. Charging the flour particles at a laminar air flow rate followed by separation under a low electric field strength enabled the production of fine protein-rich fractions with considerably higher protein contents. To further improve the separation efficiency of the navy bean protein concentrate without compromising its protein content, a two-stage tribo-electrostatic separation approach was evaluated at a laminar air flow but different plate voltages. The combined protein-rich fraction produced by the two-stage approach had a protein content of ~38% accounting for 60% of the total protein, facilitating the scale-up of this dry fractionation technique for pilot-plant applications. Protein recovery by this approach was higher than other solvent-free separation approaches and could be improved by further optimization of the flow rate and design configuration of the separator. This novel solvent-free tribo-electrostatic separation approach is of considerable commercial significant as it preserves the bio-functionality of the protein and averts the likelihood of toxic microbial contamination common in currently used wet processes.