Rapeseed protein concentrates for non-food applications prepared from pre-pressed and cold-pressed press cake via acidic precipitation and ultrafiltration
Rapeseed protein concentrates (RPCs), prepared from residual press-cakes, show excellent techno-functional properties, such as emulsification and foaming. However, food application is hindered by residual contents of anti-nutritive components. Limited research has been invested in studying RPCs as a potential ingredient in non-food applications. The present study reports RPC preparation from cold-pressed rapeseed meal (CPM) and pre-pressed rapeseed meal (PPM) as a potential ingredient for the chemical industry. Protein isolation was achieved after extraction at pH 5.7-7.0 via i) ultrafiltration or ii) a combination of acidic precipitation followed by ultrafiltration. Protein isolation yields obtained from CPM (36.5%-40.6%) were 60%-90% higher compared to PPM (19.4%-26.0%), highlighting the positive effect of low-temperature processing during defatting. Protein contents of RPCs were 75.3%-87.1% and were highest for preparations obtained through precipitation. RPCs obtained through ultrafiltration showed good solubility properties and very high values for emulsifying capacity (688-768 mL/g) as well as foaming activity (1834%-2834%). In contrast, precipitated RPCs showed lower functional values (410-445 mL/g, 888%-938%, respectively). All RPCs had excellent film-forming properties in cast-film experiments. Thus, RPCs are promising ingredients for industrial non-food applications such as adhesives, detergents, paints, varnishes and biodegradable polymers.