Disclosed is a process for the preparation of a soy protein solution, which includes: (a) extracting a soy protein source with an aqueous calcium salt solution to cause solubilisation of soy protein from the protein source and to form an aqueous soy protein solution (b) separating the aqueous soy protein solution from residual soy protein source (c) optionally diluting the separated aqueous soy protein solution (d) adjusting the pH of the separated and optionally diluted aqueous soy protein solution to a pH of 1.5 to 4.4 to provide a clear soy protein solution (e) concentrating the clear acidified aqueous soy protein solution while maintaining the ionic strength substantially constant by using a selective membrane technique and (f) diafiltering the concentrated soy protein solution to provide a concentrated and diafiltered aqueous protein solution, in which each of steps (a) to (f) is effected at a temperature of 50° to 60°C.
