Molding of baker's yeast: study of rheological characteristics and process kinetics

This paper presents a study of the molding process of baker's yeast on an industrial molding machine. The rheological properties of pressed yeast and the kinetics of their molding were investigated. It was established that yeast belongs to viscous non-Newtonian materials. Its effective viscosity significantly decreases with an increase in product moisture and temperature, as well as with an increase in shear rate. The obtained dependencies were approximated by a power function. The analysis of the process kinetics revealed a characteristic pressure distribution across the machine's working zones: from atmospheric in the loading zone to a maximum in the pressing zone, followed by a decrease. An increase in the initial yeast temperature leads to an increase in system pressure due to increased viscous friction. The product temperature increases during the molding process, reaching a maximum in the final zones due to the conversion of mechanical energy into heat, while the system does not return to its initial temperature state. The main conclusion is that to ensure stable yeast quality and reduce energy costs, it is necessary to organize heat removal directly during the molding process, for example, by cooling the working chamber. The obtained results on rheological characteristics and process kinetics are of practical value for optimizing operating modes, designing molding equipment, and developing automation systems for this technological stage.