Justyna Bauza-Kaszewska

UV-C Radiation as a Factor Reducing Microbiological Contamination of Fish Meal

Fish meals, added to feeds as a source of protein, may contain pathogenic bacteria. Therefore, effective methods for their sanitizing, such as UV-C radiation, are needed to minimize the epidemiological risk. The objective of this study was to evaluate the effect of UV-C radiation on the sanitary state of fish meals. The research materials included salmon and cod meals. Samples of the fish meals were inoculated with suspensions of Salmonella, E. coli, enterococci, and C. sporogenes spores and exposed to the following surface UV-C fluencies: 0–400 J·m−2 for bacteria and 0–5000 J·m−2 for spores. For the vegetative forms, the highest theoretical lethal UV-C dose, ranging from 670.99 to 688.36 J·m−2 depending on the meal type, was determined for Salmonella. The lowest UV-C fluency of 363.34–363.95 J·m−2 was needed for the inactivation of Enterococcus spp. Spores were considerably more resistant, and the UV-C doses necessary for inactivation were 159571.1 J·m−2 in salmon meal and 66836.9 J·m−2 in cod meal. The application of UV-C radiation for the sanitization of fish meals proved to be a relatively effective method for vegetative forms of bacteria but was practically ineffective for spores.

Effect of Microwave Radiation on Microorganisms in Fish Meals

Abstract This study was aimed at testing the effect of microwave radiation on survival of E. coli, Salmonella Enteritidis, Enterococcus spp. and Clostridium spores in two kinds of fish meals. The material used in the study consisted of samples of two kinds of fish meal – salmon and cod. In the experiment samples of both kinds of fish meals were inoculated with suspensions of tested bacteria and spores of Clostridum sporogenes. After inoculation the material was exposed to microwave radiation with a frequency of 2.45 ghz and microwave energy power of 0, 100, 180, 300, 450, 600 and 700 w, respectively, for 2.5 min for bacteria and 11 minutes for spores. then the reisolated microorganisms were counted and theoretical lethal doses of radiation were determined. among the studied vegetative forms of bacteria, the largest decreases in the numbers at the same radiation dose were observed in the rods of E. coli, whereas the smallest in enterococci. spores of Clostridium sporogenes showed a considerably higher resistance to the effect of that factor. the power of dose resulting in the complete inactivation of the studied bacteria should be about 430 kJ×g–1, and in the case of spores – 1 900 kJ×g–1.

Inactivation of Clostridium sporogenes and Geobacillus stearothermophilus spores with the use of microwave and steam sterilizers and microwave oven

Introduction. Equipment for sterilization used in medical laboratories must be absolutely effective in eliminating microorganisms and their spores. It often directly influences human health, even life. The aim of the study was to compare the effectiveness of sterilization using the steam sterilizer ASV E, microwave sterilizer EnbioJet ML1, microwave sterilizer for baby bottles and breast pumps AVENT and microwave oven. Materials and methods. Evaluation of the effectiveness of sterilization with the use of selected devices based on pressure-thermal and microwave-thermal methods was conducted, on the basis of elimination of G. stearothermophilus PCM 2104 and C. sporogenes IW 1306 spores. Results. After using the steam sterilizer, 100% inactivation of spores of both species was noted. In the case of EnbioJet ML1 sterilizer, in the test containing 106 CFU × cm–3 G. stearothermophilus spores, 1.63 × 101 CFU × cm–3 survived. The baby bottles sterilizer proved less effective. While the microwave, in the case of tests with the highest spore content, provided their inactivation only at the level of more than 70.0%. The steam sterilizer and EnbioJet ML1 sterilizer were the most effective, whereas the latter ensured a very short time of high temperature effect, which has a favorable impact on the properties of sterilized products, for example compounds decomposing in high temperature. Conclusion. Results of own, as well as other authors’ studies allow to confirm the large potential in the scope of using microwave radiation for the sterilization and disinfection of materials of various sensitivity to temperature.

Aeration as an effective method for pathogen elimination in pig slurry

Abstract The aim of this study was to investigate the effect of aeration on the survival of indicator and pathogenic microorganisms in pig slurry. After inoculation of the aerated biomass with target bacteria, samples for the microbiological analyses were collected in different time intervals for the period of 12 days. The MPN method was used to determine the number of the investigated microorganisms. The results of statistical analysis showed the lack of significant differences in the theoretical time of survival, elimination rate and the time needed for 90% reduction between different Salmonella serotypes. Theoretical survival of Salmonella Typhimurium, Salmonella Senftenberg W775 and enterococci in the aerated slurry ranged from 13 to 25 days. Enterococci were the most resistant to aeration, and their survival time, compared to salmonellas, was significantly higher.

Viability of Clostridium sporogenes spores after CaO hygienization of meat waste.

The occurrence of the pathogenic species C. perfringens and C. botulinum spores in animal by-products poses a potential epidemiological hazard. Strong entero- and neurotoxins produced by these bacteria adversely affect human health. To inactivate pathogens present in animal by-products, waste must be subjected to various methods of sanitization. The aim of the presented study was to estimate the effect of different doses of CaO on the viability of spores Clostridium sporogenes in meat wastes category 3. During the research, two doses of burnt lime were added to the poultry mince meat and meat mixed with swine blood contaminated with Clostridium sporogenes spore suspension. Half of the samples collected for microbiological analyses were buffered to achieve the pH level ~7, the other were examined without pH neutralization. To estimate the spore number, 10-fold dilution series in peptone water was prepared and heat-treated at 80 °C for 10 min. After cooling-down, one milliliter of each dilution was pour-plated onto DRCM medium solidified with agar. Statistical analysis were performed using the Statistica software. Application of 70% CaO caused complete inactivation of Clostridium spores in meat wastes after 48 hours. The highest temperature achieved during the experiment was 67 °C. Rapid alkalization of the biomass resulted in increasing pH to values exceeding 12. The effect of liming was not dependent on the meat wastes composition nor CaO dose. The experiment proved the efficiency of liming as a method of animal by-products sanitization. Application of the obtained results may help reduce the epidemiological risk and ensure safety to people handling meat wastes at each stage of their processing and utilization.