Electrophoretic removal of sinapic acid from rapeseed protein extract

• Sinapic acid can be removed from rapeseed proteins using electrodialysis. • Sinapic acid removal is achieved by transient adsorption and permeation. • Membrane surface charge affects total sinapic acid removal and protein loss. • The separation system can be upscaled by enlarging membrane surface area. Isolation of proteins from oilseeds to supply functional proteins for the food industry is essential but challenging due to the presence of anti-nutrients such as phenolic compounds. To deliver proteins, the removal of phenolic compounds is crucial. Conventionally, this is accomplished by alcohol washing; however, this is resource-intensive, may be unacceptable for some and does not provide proteins with good techno-functional properties since it alters the native protein structure. To overcome such drawbacks, gentle processing methods must be developed. In this work, we investigated the electro-separation of sinapic acid from rapeseed protein extract. A porous medium (ion exchange or ultrafiltration membrane) permitting electromigration of only sinapic acid and retaining the proteins was utilized under two different potential differences. The electro-separation of sinapic acid relied on electrostatic and electrophoretic forces, which cause their adsorption and permeation. Among the treatments, 1.5 V over an anion exchange membrane showed the best performance, providing considerable sinapic acid removal (34.0 ± 4.0 wt%) while maintaining the protein content and pH stability. A larger system with a larger membrane surface area yielded as high as 90.3 ± 3.8 wt% of sinapic acid removal within 240 min while retaining 88.8 ± 7.6 wt% of the proteins.