Use of UV/UV-LED radiation for reduction of microorganisms on eggs (UVegg)

The task of the project was to develop and establish techniques and procedures for the practical application of UV light (in particular the UV-C waveband) and to demonstrate the efficiency of the reduction of (zoonotic) bacterial microorganisms and the safety of a treatment of table eggs using UV-C LED radiation. The BfRshort forGerman Federal Institute for Risk Assessment carried out the contamination scenarios of table eggs with Salmonella, whereas contamination scenarios for Campylobacter, ESBL-producing E. colishort forEscherichia coli, Enterococci and MRSAshort forMethicillin-resistant Staphylococcus aureus were carried out at the Institute for Animal and Environmental Hygiene (ITU) and the Institute for Food Safety and Hygiene (ILH) of the Freie Universität Berlin, Department of Veterinary Medicine. The qualitative effects of UV-C/UV-C LED treatment on table eggs were determined by the three project participants BfRshort forGerman Federal Institute for Risk Assessment, ITU and ILH.

During the preliminary investigations at the FU-Berlin, a suitable laboratory method and or contamination model for table eggs was established under different contamination scenarios for the selected pathogen. Three methods were comparatively investigated, whereas the swab method showed the highest bacterial recovery rates with a method detection limit of 5 cfu/cm2. At the BfRshort forGerman Federal Institute for Risk Assessment, a S. Enteritidis and a S. Typhimurium strain were selected for the contamination scenarios of table eggs. The two strains were isolated from chicken eggs and were obtained from the strain collection of the National Reference Laboratory for Salmonella. Experimental contamination of the egg surface was performed with defined bacterial suspensions in three different contamination doses, each of which had additionally no (PBS only), low (3 g bovine serum albumin (BSA)/liter), and high organic load (10 g BSA/L and 10 g yeast extract/L). A recovery rate of 100, 10000 and 1000000 cfu/cm2 of the bacterial strain used with no UV exposureClose dialogexposureExposureTo glossary and no organic load was targeted to analyze the effect of low and high organic load on the recovery rate as well as the effect of conventional UV-C to UV-C LED. The recovery rates for the two Salmonella strains could be stably reproduced without UV exposure. Statistical analysis confirmed significant differences in recovery rates between the bacteria used, as well as contamination doses and exposure scenarios. High levels of contamination, as well as high organic loads, therefore have a protective effect on the pathogens, leading to higher recovery rates, and smaller losses, respectively. After successful establishment of the contamination scenarios, the influence of treatment with conventional UV-C light and UV-C LED on the reduction of the relevant zoonotic pathogens was investigated. For UV-C treatment, a mercury vapor lamp (wavelength 254 nmshort fornanometre) with the intensity of ≈ 5.0 mW/cm²short forsquare centimetre and a UV-C LED module (wavelength 280 nmshort fornanometre) with an intensity of ≈ 2.4 mW/cm²short forsquare centimetre were used. The irradiation time was ≈ 5 seconds and the distance to the UV-C source was ≈ 5 cm. During irradiation, the eggs were rotated at a rotational speed of ≈ 1.6 revolutions per second. These parameters were adopted because they represent the parameters of the egg packing station of Löwendorfer Geflügelhof GmbH (project partner). The constuction and the set-up of the test stand in the laboratory of the Institute for Animal and Environmental Hygiene, where the laboratory tests took place, was carried out by the collaborative partners SKS and OSA. In summary, it can be stated that the treatment by conventional UV-C light using mercury vapor lamps as well as by UV-C LED lamps showed a decontaminating effect on experimentally contaminated table eggs. Both UV-C methods achieved reductions of the numbers of S. Enteritidis and S. Typhimurium on table eggs. However, these are dependent on the bacterial contamination level and the organic load of the eggs. Elimination of both Samonella serovars up to the detection limit was possible at low bacterial counts and without an organic load on the individual eggs. These results provide the basis for a safe application of the tested UV-C LED source for decontamination of table eggs in practice with the attention to bacterial contamination level and organic load. The investigation of the qualitative effects of UV-C and UV-C LED treatment on the sensory quality of boiled table eggs was analyzed by the BfRshort forGerman Federal Institute for Risk Assessment and the two collaborators of the FU-Berlin by means of a triangular test according to DIN EN ISO 4120:2007-10. The sensory quality of the eggs remained unaffected after both UV-C and UV-C LED treatment, even with a tenfold increase in treatment time (50 seconds). Optimization of the UV-C treatment (distance to the UV-C source and the irradiation time) and adjustment of the UV-C (LED) source (wavelength and intensity) could lead to increase the possible reductions. However, this requirement is associated with additional laboratory testing.