The present invention relates to an improved method of producing products comprising a target protein (TP) capable of crystallising under salting-in conditions by crystallisation of the TP. The invention makes use of at least two different TP-containing protein feeds which are mixed to prepare a supersaturated protein solution in which TP is crystallized. One of the protein feeds must have a pH of at least the pH providing the maximum crystallisation yield of the TP (pH.sub.MCY,TP) plus 0.1 and one of the protein feeds must have a pH of at most pH.sub.MCY,TP minus 0.1.