Heat-induced gelation of rapeseed proteins: Effect of protein interaction and acetylation

The gel-forming abilities of a rapeseed protein isolate, composed of 70% globulin (cruciferin) and 30% albumin (napin), and their individual protein components, were investigated. The influence of acetylation upon the gelation properties was also studied. Highest gel strength (measured as shear modulus) of the isolate was obtained at pH values around 9, which is between the isoelectric points of both major proteins. Purified cruciferin gave the highest shear modulus values, with maxima at pH 6 and 8. Weak and poorly stable gels exhibiting strong hysteresis were obtained with isolated napin. Acetylation resulted in a pH shift of the shear modulus maximum of the protein isolate to about 6. The gelation temperature of the acetylated isolate had the highest pH and concentration dependence compared with the other proteins.