Study on the Kinetics, Hydrodynamics and Mass Transfer of the Process of Zucchini Fruits Saturation With Sucrose From an Aqueous Solution

Abstract

Processes of sucrose diffusion inside plant fruits and their generalization require special attention, namely theoretical generalization of experimental data and organization of energy-saving production of candied fruits while preserving the quality of the finished product. This work deals with the experimental and theoretical studies of the kinetics, hydrodynamics and mass transfer of the process of zucchini fruits saturation with sucrose from an aqueous solution. Experimental studies were conducted in static and dynamic modes. In static mode, fruit saturation occurs from an aqueous solution of sucrose in a stationary state of the solution. Dynamic mode occurs under conditions of air bubbling of an aqueous sucrose solution. Specific heat consumption of the studied modes of saturation of zucchini fruits in sugar syrup was theoretically calculated. The kinetic process of changes in the sucrose concentration in zucchini fruits at different rates of air supply for bubbling was studied in detail. It was found that the process kinetics occur in the regions of external and internal diffusion. Based on Fick's law, a generalization of the saturation processes of the particles of zucchini fruits with sucrose in the external diffusion region was carried out using the similarity theory. The existence of three hydrodynamic regimes during fruit saturation in dynamic mode was proved. Criterion equations were derived allowing us to theoretically calculate the mass transfer coefficient under the conditions of three hydrodynamic regimes. From technological and economic points of view, the most expedient process of zucchini fruit particles saturation with sucrose occurs at a syrup temperature of 70°С and a rate of air flow for bubbling from 6 to 8 m/s. The derived criterion equation allows to establish the numerical value of the air pressure for bubbling depending on the air supply rate.