Comparison of the effect of acylation and phosphorylation on surface pressure, surface potential and foaming properties of protein isolates from rapeseed (Brassica napus)

A protein isolate from rapeseed was exhaustively modified by acetylation, succinylation and phosphorylation. Changes in protein solubility, adsorption kinetics, surface pressure and surface potential of monolayer, wetting and foaming properties due to chemical modification were studied. Chemical modification distinctly increased the solubility of the rapeseed protein in the alkaline pH range. Acylation increased the reduction of the surface tension. An overall improved pressure transformation and increase in surface potential in monolayer after modification was observed whereby the highest changes were achieved after succinylation. The wettability with water of protein coated hydrophobic glass substrates could be improved by succinylation and phosphorylation. Chemical modification increased the foam capacity and foam expansion of the protein. A higher foam stability was only measured after acetylation and phosphorylation. Adsorption kinetics and surface potential could be related well to the properties of protein films on hydrophobic substrates as well as in foams. (C) 2002 Elsevier Science B.V. All rights reserved.