Soy protein isolate was physically (heat pretreatment) and chemically
(urea, guanidine.HCl, and cleavage of SS bonds) modified in order to d
issociate subunits, unfold the protein and improve surface properties:
hydrophobicity, emulsification capability, and stability. Heat pretre
atment as well as chemical treatment with urea or guanidine.HCl or red
uction of disulphide bonds, will improve emulsification performance in
comparison to native soy protein isolate. Significant differences in
reduction of surface tension of water in the presence of native and mo
dified proteins were observed (45 and 35 dynes/cm respectively). Measu
rements of fluorescence indicated that the relative hydrophobicity of
the soy protein was also improved (from 600 to 1360) after heat pretre
atment or contacting the soy protein with 8M urea solution.