Molecular transfer processes in liquid nutrient media in the yeast and beer industries. 2. Study of the rheological properties for aqueous solutions of molasses and concentrated beer wort

Abstract

The article is a continuation of the research in the field of comprehensive study of the properties characterizing the processes of momentum, thermal energy, and mass transfer in liquid nutrient media of biotechnological production. Experimental studies of the rheological properties for liquid nutrient media have been conducted. Beet molasses with an initial concentration of dry substances (DS) of 77.7 wt.% and concentrated malt extract of beer wort with an initial concentration of DS 81 wt.% were selected as objects of research. The temperature variation range was 10 to 70℃. The viscosity of the mentioned objects was measured with a HÖPPLER® KF 3.2 ball viscometer and also for highly viscous solutions on a Rheotest RN 4.1 viscometer, as a result of which the graphical dependences on temperature and DS concentration, as well as the gradient of shear rate were obtained. It has been established that the viscosity of these two nutrient media (beet molasses and beer wort), different in the method of obtaining the composition, has not only a similar pattern of change in the dynamic viscosity coefficient depending on temperature and content of soluble solids, but also a comparable numerical range of values. The boundaries of variation for the shear rate gradient, in which the studied objects behave as non-Newtonian fluids, from 1 to 100s-1, have been determined. The results obtained are of interest both from the point of view of fundamental science about the development of the theory of the liquid state of matter and applied, in terms of engineering calculations and the design of biotechnological equipment.