Functional and bioactive properties of rapeseed protein concentrates and sensory analysis of food application with rapeseed protein concentrates

In order to investigate the use of rapeseed (Brassica napus) protein from oil industry waste for food applications, two rapeseed cultivars (Express, Lion) were pretreated to remove the hulls and oil. Rapeseed protein concentrates were then prepared by washing with 450 ml/l isopropanol. A portion of each protein concentrate was steamed before undergoing isopropanol treatment to deactivate myrosinase. Deactivation of myrosinase prevents glucosinolate decomposition and improves the extractability of sinapin acids. Lion rapeseed protein concentrates showed higher water and oil binding capacities than Express protein concentrates. The steaming process reduced the oil binding capacity, emulsification capacity and protein solubility. When steamed rapeseed protein concentrate was added to sausage preparations in place of casein, sensory analysis showed that the rapeseed protein sausage had improved taste, good texture and a characteristic aroma. Hydrolysed de-oiled rapeseed and protein concentrates were prepared using gastrointestinal enzymes. The cholate binding capacity, angiotensin converting enzyme (ACE) inhibition and DPPH radical scavenging activity were then investigated. Pepsin-hydrolysed protein concentrates showed the strongest ACE inhibition. Hydrolysed protein concentrates showed 2.3-3.0 times higher DPPH radical scavenging activity than non-hydrolysed samples. The cholate binding capacity was not affected by the hydrolysis. The steaming process did not significantly alter the bioactivities.