The potentiality of treatments with NH4OH solutions for improving the quality of protein concentrates from Candida utilis biomass was studied. The effects of NH4OH concentration, reaction time, and temperature on both biomass recovery and composition of processed samples (including nucleic acid and protein contents) were studied. The results obtained were used to develop empirical models providing a quantitative interpretation of the interrelationships among the variables involved. Additional discussion of the reaction selectivity is provided. Under selected conditions, 96% of nucleic acid removal was achieved with 88% protein recovery. The treated cells were high in vitro digestibility and showed an amino acid profile similar to that of untreated biomass.