This supports results by Birmpa et al. (2013), who observed a log reduction of only up to 1.4 log CFU/g in E. coli, L. innocua, Salmonella Enteritidis and Staphylococcus aureus on the surface of strawberries at UV-C light intensities of 72 kJ/m2.
A similar result was observed by Syamaladevi et al. (2015) for the plant pathogen P. expansum.
Limited E. coli O157:H7 reduction (1.1 log CFU/g) was also reported on rough surfaces (mushroom caps) with a UV-C dose of up to 3.15 kJ/m2 (Guan et al., 2012).
Awound or roughened fruit surface shields and partially protects microorganisms during UV-C exposure (Syamaladevi et al., 2013).
However,we observed an interesting pattern with L. monocytogenes, with the largest E90 on strawberry surfaces.
This may be due to the higher resistance of Listeria spp. to UV-C treatment (Gabriel and Nakano, 2009; Guerrero-Beltrán and Barbosa-Cánovas,2005).