Comparative structural, emulsifying, and biological properties of 2 major canola proteins, cruciferin and napin

Canola is an economically important farm-gate crop in Canada. To further explore the potential of canola protein as value-added food and nutraceutical ingredients, a better understanding of fundamental properties of 2 major canola proteins is necessary. Two major protein components, cruciferin and napin, were isolated from defatted canola meal by Sephacryl S-300 gel filtration chromatography. SDS-PAGE showed that cruciferin consists of more than 10 polypeptides, and noncovalent links are more important than disulphide bonds in stabilizing the structural conformation. Napin consists of 2 polypeptides and is stabilized primarily by disulphide bonds. Purified cruciferin showed 1 major endothermic peak at 91 degrees C compared with that of 110 degrees C for napin. Emulsion prepared by cruciferin showed significant higher specific surface area and lower particle size than that of napin. The study indicated that the presence of napin could detrimentally affect the emulsion stability of canola protein isolates. Hydrolysates from cruciferin and napin showed potent angiotensin I-converting enzyme inhibitory activity (IC(50): 0.035 and 0.029 mg/mL, respectively), but weaker than that of canola protein isolate hydrolysate (IC(50): 0.015 mg/mL).