The invention therefore relates to protein-containing powders, wherein the proportion of phenylalanine is at least 30% (w/w), or at least 40% (w/w). It has been shown that phenylalanine-containing powders, particularly after spray drying, are very suitable in terms of their aerodynamic characteristics and protein stabilization for preparing powders or protein compositions with improved aerodynamic properties. The main component is phenylalanine and the optional further component is an excipient which has good water-solubility compared with phenylalanine, preferably a sugar or a polyol.