The functional properties of food proteins can be modified by chemical, physical and biotechnological methods. While chemical modifications are problematic on toxicological grounds the other two allow the modelling of specific functional requirements for different foods. The basis for these modifications is the knowledge of compositional and structural features of the protein system involved. Physical and biotechnological procedures include specific heat treatments under definded pH‐ and ionic conditions, protein fractionations and enzymatic processes like controlled proteolysis, dephosphorylation, and the modelling of the new protein and peptide structures by the plastein reaction. The resultant changes in physicochemical properties of the proteins have a decisive impact on their functional behavior in food systems, e.g. solubility, foam formation and stabilization, emulsifying and gelling properties as well as on nutritional parameters.