Study of freeze-drying process of bacterial concentrates in the apparatus using thermoelectric modules

Abstract

The method of lyophilization is the only possible way to preserve starters, microbiological cultures, probiotics, enzyme preparations, hormones, vaccines, antibiotics, enzymes and other biological materials. An essential aspect of the implementation of the lyophilization method is the preservation of the biological activity of materials. In the case of bacterial concentrates, this indicator is estimated by the number of viable cells at the end of the dehydration process and subsequent storage. Freezing is the first and most important stage of lyophilisation, during which the final product structure is formed, affecting the quality of the material. Freezing rate and temperature are determined individually for each preparation in order to select conditions ensuring maximum safety of product structural integrity. The purpose of researches is a complex definition of reasonable intervals of parameters of freeze-drying of bacterial concentrates that will allow optimizing this technological process. Criteria of optimization are qualitative parameters of the product and energy consumption for freeze-drying. Also, a comparative analysis of the energy efficiency of the developed freeze-dryer and its existing analogues has been performed. Each of these substances has a specific eutectic point, which leads to a eutectic zone of concentrates. Thus, the freezing temperature of bacterial concentrates should be several degrees below the upper eutectic point, i.e. in the range of minus 39 to minus 42 °C. During the freeze-drying, the following rational parameters were established: residual pressure in the chamber 0.05-0.06 mbar, the final temperature of the material 34-35 °C, the temperature on the condenser surface minus 55 °C.