Tomato concentrate and baker's yeast suspension were dried in the laboratory scale Mechanically Spouted Bed dryer with inert packing. Due to a large contact surface provided by the inert particles, very fast drying process can be achieved, ifthe thickness of the wet coating formed on the surface of the inert packing is film–like. The diffution resistance can be then considered negligible and drying can be performed at “quad–constant” rate. Derived fiom hydrodynamic characteristics the contact time between hot air and the wet coating is very short, therefore gentle drymg process can be performed. The quality of the dried yeast was controlled by counting the living cells (relative viabilny) and by measurement of the dough rise time. During continuous drying of thermoplastic tomato pure the “case hardening” periods could be shortened and tomato powder with insignificant quality loss was produced.