Shown is a method for producing protein preparations having essentially constant functional properties for technical applications within a broad pH range from about pH 3 to pH 10 by means of extraction from a starting product which contains protein, notably legumes, grains or oilseed. The invention is distinguished by the protein-containing starting product undergoing at least one liquid extraction step and that the raffinate and/or extract obtained thereby undergoes at least one membrane separation process in which a residue is obtained or undergoes thermal upgrading in which a concentrate is obtained and that the residue or the concentrate contain the protein preparations having the desired functional properties.