The Correlation between Tribo-charging of Agricultural Particles and their Classification Behavior via the Tribo-electrostatic Separation Approach

The tribo-electrostatic separation (TES) could be effectively used as a waste- and chemical-free approach in dry fractionation of plant proteins, producing functional plant protein concentrates at their native states. Through TES, agro-material particles are charged using a tribo-charger tube via pneumatic transfer and fractionated under an electric field. Our Team at Howard University identified the crucial factors in optimal plant protein separation from milled cereal groats, legumes, and oilseed meals through TES. Milled legumes exhibited the highest protein enrichment due to differences in particle size and chargeability between protein and starch granules. The effectiveness of protein enrichment in cereal groats and oilseed meals is limited by the uniform particle size distribution of dietary fiber and protein particles, which restricts their separation based on chargeability variations rather than chargeability and particle sizes. Our results indicated that sieving large bran particles from milled cereal groats could significantly improve the protein enrichment in the endosperm-enriched fraction of the cereals by TES.  

Our tribo-charging analysis of agricultural constituent particles represented a different charging behavior between protein and starch particles in contact with most tested tribo-charger materials. At the same time, this difference was limited between proteins and dietary fibers primarily due to the presence of lignin and hemicellulose. The TES results of binary mixture models of protein-starch and protein-fiber indicated the maximum loss when one agro-particle dominated the mixture. It implies the prevalence of particle-material collisions, leading to the adhesion of particles to the tube wall. The type of tribo-charger material was ineffective in protein enrichment from mixtures with protein-fiber and protein-starch weight ratios of 3:7 to 7:3, highlighting particle-particle interactions. The presented findings could assist in developing an optimal TES method for cereals, legumes, and oilseed meals.

Acknowledgement:

The project was funded through USDA-NIFA-AFRI Grant, #2020-67021-31141, and NSF Grant, #HBCU-UP-RIA-1900894.