On the issue of studying the forms of moisture coupling in thermolabile heterogeneous products

Abstract

The article deals with issues related to the study of the connection forms of moisture removed during the drying process of thermolabile heterogeneous products. The difficulties, emerging while developing drying process controlling methods, optimizing energy, material costs, and temperature regimes, necessitate further research. It is shown that the existing methods of studying the forms of moisture connection with the material have significant drawbacks and generally give a qualitative assessment of the state of moisture in the material or are very time-consuming and require long-term laboratory studies. An approach to determining the forms of moisture bond in the material based on graph-analytical analysis of the drying kinetics is proposed, which allows qualitative and quantitative assessment of the state of moisture in the product. With the help of a graphical editor, typical drying kinetics curves were processed and the dependences of the value that characterizes the speed of change in the drying rate on the moisture content of the product were obtained. It is proposed to introduce a new value in the drying theory - drying acceleration. The analysis of the obtained curves testifies to the presence of extremes and inflection points corresponding to the critical moisture content, as well as the presence of areas with slowing or accelerating changes in the drying rate, allowing setting intervals for removing moisture with different binding energy. The approach considered in the article to determining the forms of moisture communication in the material will not only give a qualitative and quantitative assessment of the state of moisture in products, but also reduce the time for analysis and improve the accuracy of the results.

Application of drying acceleration to study the forms of moisture bond in currant fruits

“…Then, for a further and deeper analysis of the kinetics of the drying process of currant fruits, we use a value that determines the rate of change in the drying rate, that is, the first derivative of the drying rate with respect to moisture content 𝑑𝑁 𝑑𝑈 or the second derivative of moisture. The term «drying acceleration» is applicable to this value [10].…”