The interdependence of the main heat engineering parameters of dehydration and the quality indices of materials is analyzed. The classification of different microbiological materials as drying objects is proposed and based on their thermo-and xerolability. The critical residual moisture content is proved to be one of the main factors predetermining the choice of the dehydration method for living systems. Of special interest is the comparison of the experimental data for the effect of residual moisture content, the microorganism viability and for the behaviour of sorption isotherms, which would reveal a possible physical mechanism of the microorganism death when moisture is removed from biomass.