Continuous counter-current electrophoretic separation of oleosomes and proteins from oilseeds

Oilseeds, with their high content of oil and protein, will play an important role in the transition to plant based foods. Currently, seed oil extraction involves elevated temperatures and the use of organic solvents, which degrade the quality of both oils and proteins. To take full advantage of the oilseeds, a gentler process is needed. We here propose a mild alkaline extraction followed by a continuous electrophoretic separation process that is based on differences in electrophoretic mobility and recovers intact oleosomes and proteins from the seeds. Rapeseed oleosomes and proteins are both negatively charged at pH ≥ 5, yet exhibit significantly different electrophoretic mobility. Therefore, separation can be achieved by imposing a counter-current hydrodynamic flow rate between their electrophoresis rate. Thus, the compounds with higher mobility, oleosomes, are retained by the electric field, and the compounds with lower mobility, proteins, go along with the flow. The separation was modeled using the Nernst-Planck equation and demonstrated using a PDMS-based microfluidic system. Both the modeling and the experimental studies confirmed that the direction and rate of migration of the compounds can be steered by the electric field strength and the convective flow velocity. The proposed electrophoretic approach is feasible and scaleable, and may be a novel path to separate differently charged components under mild conditions, thereby preserving their original native properties.