Photoinactivation of E. coli on bagged Valerianella locusta and on Cichorium intybus var. foliosum with 222 and 254 nm

In recent years, serious disease outbreaks have occurred caused by pathogens like Escherichia coli, Listeria and Salmonella. The EHEC epidemic in 2011, caused by E. coli, resulted in the death of about 50 people. Therefore, food disinfection is important. A possible approach is disinfection by UV radiation, which is a fast and environmentally technique.

The objective of this work is to investigate the germicidal effect on E. coli x pGLO on bagged lettuce and on seedlings with the emerging Far-UVC (222 nm) in comparison to the widespread 254 nm UVC variant. In contrast to 254 nm radiation, Far-UVC-radiation is known to inactivate pathogens without harming humans. To investigate this germicidal effect of this kind of UV radiation, packed field salad and chicory seedlings were inoculated with E. coli x pGLO and irradiated.

We found that a 222 nm irradiation of 40 mJ/cm² led to an E. coli reduction of up to 99 % on seedlings. Similar experimental results were obtained for the packaged lettuce. For irradiation with 254 nm, a germ reduction of more than 90 % were observed at a dose of 7 mJ/cm² for packaged lettuce. When applied this wavelength to the seedlings, a reduction of 99 % could be achieved with the same reduction dose.

UVC radiation seems to be suitable for germ reduction on plants. Further investigations are necessary to see, if there is a difference between young and older plants, but also to see the impact on other parts of the plant beside the leaves.