Method for preparing tryptophan rich peptides

Described is a method for selectively isolating tryptophan containing peptides from an aqueous peptide mixture, comprising the steps of: a) controlling the pH of the aqueous peptide mixture to 4,0-6,0, forming a precipitate of tryptophan containing peptides; and b) isolation of the precipitated peptides. The aqueous peptide mixture is preferably obtained by enzymatic cleavage at acidic pH of a protein source. Further, peptides having a Trp content of 8-15 w/w% and the use thereof as food additive and as active ingredient in a medicament are described.