Development of microwave technology of selective heating the components of heterogeneous media

Abstract

The relevance of solving the technological problem of guaranteed inactivation of microflora by heating in liquid media and the preservation of their useful components, in particular, in wine materials, is substantiated. Traditional heat treatment with heating up to 70...75 °C leads to a deterioration in the properties of the medium due to the thermal decomposition of its useful components. Newer is the technology of heating by the energy of the microwave field in the working chamber. But its significant drawback is the formation of standing waves in the metal chamber, causing local zones of overheating in places of maxima and underheating in places of wave minima. The consequence of this is the deterioration of the chemical composition of products and unsatisfactory inactivation of microflora. The elimination of these disadvantages of microwave processing of media is proposed to be carried out in a non-resonant chamber developed by the authors. Selective heating in the new chamber is produced by the energy of a uniform microwave field. At the same time, there are no local overheating and underheating of products. The technical implementation of a non-resonant type chamber involves the concentration of field energy in the volume of production, the conversion of the ballast field energy into thermal energy and its utilization. The work includes theoretical substantiation and experimental confirmation of the advantages of the new technology compared to the traditional one. Selective heating of products in a non-resonant working chamber entails the possibility of reducing the temperature required for guaranteed inactivation of microflora by 25...30 °C. This helps to preserve the components of the product due to the absence of overheating and reduce energy costs. In addition, it provides: exclusion of harmful radiation from the working chamber; prevention of self-overheating of the generator and exclusion of the dependence of the energy efficiency of the chamber on the level of its loading with products.

Application of an Electromagnetic Field for Extending the Shelf-Life of Not from Concentrate (NFC) Apple Juice

“…According to Guo et al (2017) [47], microwaves affect microorganisms through different mechanisms: selective heating, electroporation and magnetic field coupling. The selective heating effect can lead to faster heating of microorganisms that absorb microwave energy compared to the surrounding liquid, thereby reaching pasteurization temperatures [48]. Electroporation induces the formation of pores in the cell walls of microorganisms, resulting in the leakage of cell contents and, consequently, cell lysis [49].…”