Electrophoretic Dephenolization of Rapeseed Proteins: The Influence of Ionic Strength on Sinapic Acid Electromigration

Next to the oil, proteins are the other most valuable constituents of oil-bearing seeds, such as rapeseed. Current recovery methods often employ conditions (temperature, pH, and use of solvents) that degrade the functionality of the proteins. Electrophoretic processes that utilize the electrical charge of the components as an additional driving force offer an alternative. Sinapic acid (SA), the predominant phenolic compound in rapeseed, can be removed by electrophoretic permeation through a membrane. As the raw juice from the rapeseeds may have differing ionic strengths, it is important to analyze its effect on SA electromigration and removal under changing ionic concentrations. We examined SA solutions with five different ion concentrations (5, 10, 20, 30, and 40 mM). The highest SA removal of 57.2 ± 3.4 wt% was achieved at 5 mM buffer, which decreased between 5 and 20 mM, and then reached a plateau. The feasibility of the dephenolization principle was then demonstrated with a practical rapeseed protein extract. 30.3 ± 4.1 wt% of SA and 14.9 ± 2.8 wt% of the natural phenolics were removed in 4 h of operation while retaining 96.5 ± 0.9 wt% of the proteins. The principle is expected to be easily extended toward full removal of SA and other phenols.