Due to the special importance of food in the emergence of acute intestinal infectious diseases and bacterial food poisoning, special attention is paid to the microbiological purity monitoring of food raw materials and food products. Ionizing radiation processing of food – is a promising technology for combating both microorganisms causing spoilage and pathogenic and opportunistic microorganisms – pathogens of dangerous diseases. However, work with vegetative forms of these microorganisms to study the effects of ionizing radiation is difficult because of the need to use in experiments only actively growing culture, which is sensitive to various environmental factors. When studying the effect of ionizing radiation on the microflora of food products, this study describes the investigation of the possibility of using as a test-culture the ascospores of the fungus Aspergillus fischeri instead of vegetative forms of pathogenic and opportunistic cultures. Ascospores of the fungus Aspergillus fischeri are used as a test culture in the development of pasteurization regimes of fruit and vegetable products. A. fischeri ascospores have been shown to have higher resistance to ionizing radiation in the range from 1 to 5 kGy at capacity 10 MeV in comparison with Salmonella enterica, Escherichia coli and Listeria monocytogenes cells. Therefore, in the development of ionizing radiation food processing regimes it is recommended to use ascospores of the fungus A. fischeri as a test culture instead of vegetative forms of bacteria.

The use of radiation technologies in agriculture and the food industry is a common worldwide trend. Global reduction of food products at all stages of production has reached 30 percent. Especially significant reduction is in fruits and vegetables production. Radiation treatment of food products helps to suppress the development of pathogenic microorganisms as a result it extends the storage periods. Despite numerous studies in this field, existing methods of irradiation require optimization in order to ensure the possibility of using irradiation for all types of fruit and vegetable products. This research work is focused on the study of the effectiveness of irradiation of model systems containing conditionally pathogenic microflora by electron beams with an energy of 10 MeV. The aim of these developments is to study the effectiveness of electron beam irradiation application to suppress pathogenic microorganisms that cause bacterial contamination of food products. In this regard, the following tasks were set: to determine the degree of investigated microorganism’s stability and to find the differences between horizontal and vertical positions of the samples during irradiation. The developments showed that Salmonella and E. coli strains were the most resistant to ionizing radiation, while S. aureus strains were less resistant. The difference of obtained results for vertical and horizontal positioning of the samples was noted. When processing samples with studied strains of cultures in the dose range from 4 to 5 kGy, there is an increase in the growth of microorganisms for all processing conditions. In the remaining studied ranges their inhibition are observed. It is important to take into account not only the effectiveness of the oppression of microflora on specific products, but also the efficiency of the installation for a specific sample.

Studies on the inhibition effectiveness of the initial degree of inoculation of the Salmonella microorganism were carried out. In this paper, the irradiation efficiency of model systems with electron beams with beam energy of 6.5 and 10 MeV was studied. The investigations were carried out at UELV-10-10-C-70 accelerator at Frumkin Institute of Physical Chemistry and Electrochemistry of Russian Academy of Sciences (IPCE RAS) with an average beam power of 6.5 MeV and at radiation-technological center with an electron accelerator UELR-10-10-40 at A.I. Burnazyan Federal Medical Biophysical Centre of Federal Medical Biological Agency with an average electron energy of 10 MeV. The conducted researches on studying and revealing the dependence of inhibition of pathogenic microflora, irradiation with different intensity, on the structure (density) of the studied samples, which model liquid and solid nutrient media. The study used a strain Salmonella enterica subsp. Enterica serovar Typhimurium. The results of the effective inhibition of the initial degree of contamination for the two plants were obtained. Studies have shown that the effectiveness of inhibition of Salmonella culture can vary depending on the characteristics of electron beams. For example, when samples were irradiated with electrons with energy of 6.5 and 10 MeV at doses from 3 to 7 kGy, various results of the inhibition effectiveness of Salmonella culture on media with different work were obtained. When processing samples with studied strains of cultures in the dose range from 4 to 5 kGy, there is an increase in the growth of microorganisms for all processing conditions. In the remaining studied ranges their inhibition are observed. It is important to take into account not only the effectiveness of the oppression of microflora on specific products, but also the efficiency of the installation for a specific sample.

Ultraviolet radiation has long proven itself as a technological process that allows you to reduce a significant amount or completely inhibit unwanted microorganisms, however, this technology is mainly used for disinfection of air and surfaces in industrial enterprises. The use of food processing with ultraviolet light is poorly developed, this is due to a number of limitations, one of which is the small depth of penetration of ultraviolet radiation. This circumstance introduces a number of restrictions and requires additional research for the active introduction of UV radiation in the food industry. The aim of the work: to study the dynamics of inhibition of native microflora of raw materials during UV treatment with various doses; to determine the degree of development of residual microflora during storage of UV-treated food products. Objects of research: model media containing native microflora of raw materials and fresh mushrooms. An improved UV treatment mode is proposed to reduce the surface injury of fresh mushrooms and ensure their microbiological stability of champignons during storage. The obtained results allowed us to establish the regularities of inhibition of native microflora on the surface of model media and fresh mushrooms depending on the distance to the UV radiation source, the time of irradiation, and the accumulated dose. It is noted that the dynamics of inhibition of native microflora on the surface of model media is not linear, and "Plateau" zones are marked. When developing a technology for processing fresh mushrooms, it is recommended to use a UV source with an accumulated radiation dose of 500 Dg/m2.

The research results concerning the application of physical methods of plant raw materials influencing - fresh beetroot - to inhibit microorganisms of Salmonella genus were presented in the work. Pathogenic microorganisms of Salmonella genus pose a threat to humans, being causative agents of typhoid fever, paratyphoid fever and other salmonellosis. The use of effective and available physical methods of influence in the fruit and vegetable processing technology allows us to ensure the maximum conservation of physiologically valuable components of the raw material and its safety. Microwave (microwave field) and ultraviolet radiation were chosen as physical methods for research. The sterilizing effect of the microwave field was clearly expressed - the bacteria survival after such a treatment was 2 or more times less than during heat treatment. Treatment with ultraviolet radiation has a bactericidal effect and is characterized by a minimal effect on the plant materials organoleptic properties. A comparative assessment of the effectiveness of the inhibition of the Salmonella test culture on diced fresh beets after treatment with the selected physical methods was carried out during the study. The samples temperature rose up to 43–46 °C under the influence of a microwave field in the selected mode with a power of 400 W, a duration of 40 s, and a flux density of 0.44 W / cm2. Treatment with ultraviolet (UV) radiation in the C-band (wavelength 253.7 nm) was carried out for 15 min with a dose of 50 kJ / m2 with a total power of ultraviolet lamps equal to 60 V. Processing of fresh chopped beets with UV radiation reduced the number of microorganisms by 5 orders of magnitude from the initial amount. Processing in a microwave field allowed to reduce the initial seed contamination of raw materials by 7 orders of magnitude. Sequential processing in a microwave field and subsequent ultraviolet radiation allowed us to reduce the initial beets seedling by 8 orders of magnitude. The combination of processing methods (microwave + UV) showed the effectiveness of their application to reduce pathogenic microflora.