Enhanced Protein Extraction from Oilseed Cakes Using Glycerol–Choline Chloride Deep Eutectic Solvents: A Biorefinery Approach

The enhanced extraction of proteins from rapeseed cake (RC) and evening primrose cake (EC) using a glycerol–choline chloride deep eutectic solvent (DES, glyceline) is reported. Protein-rich precipitates were obtained by adding water (antisolvent) to the DES extract derived at different processing temperatures. The presence of proteins in precipitates has been confirmed by several techniques, such as NMR, ATR-IR, TGA, CHN, and SDS-PAGE. Yield of precipitates improved with increasing temperature of treatment, reaching a maximum of 20% and 35% at 140 °C from RC and EC, respectively. In general, the protein content of the extracts was ca. 40–50%, which is up to 20% more than the starting materials. SDS-PAGE confirmed that glyceline selectively extracted cruciferin proteins (ca. 16–33 kDa) from RC, while proteins with variable molecular weight (10–40 kDa) were identified in EC extracts. As a potential application, cruciferin-rich RCP60 and RCP100 could be incorporated into final food formulations as a source of protein due to its light color.