Process for purifying microbial protein isolates

The invention relates to a process for the purification of microbial protein isolates, by which substances with an undesirable odor and taste are removed from microbial protein materials, by treating the latter with aqueous solutions containing a phosphate and / or hydrophilic aliphatic substances, with 2 ... 6 carbon atoms containing at least two functional groups from the hydroxyl series, formyl keto and carboxy. Preferred aliphatic extraction auxiliaries are tasting acids, sugars and polyols, and ortho- and diphosphates are phosphates. The extraction can take place in a reduction of the nucleic acid content of the defatted cell masses.