Effectiveness of two UV-C light-emitting diodes (LED) systems in inactivating fungal conidia on polyethylene terephthalate

The present study aimed to assess the effects of two UV-C LED systems on three food-spoilage fungi (Hyphopichia burtonii, Penicillium brevicompactum, Aspergillus brasiliensis) that can contaminate food packaging materials. The UV-C LED systems were used at two distinct light intensities (9.0 mW/cm(2) and 5.5 mW/cm(2)) for up to 800 s. Fungal conidia were deposited on polyethylene terephthalate lids as either a single (4-5 log CFU/lid) or a multiple layer of cells (5-6 log CFU/lid) to evaluate any difference due to a potential "shadow effect ". In the tests performed, A. brasiliensis was the most resistant fungus to the effects of UV-C LED irradiation, with its 1D-value varying from 23 to 58 s (9.0 mW/cm(2)) and from 46 to 58 s (5.5 mW/cm(2)) regardless of the light source used or the type of inoculum. In contrast, H. burtonii and P. brevicompactum were inactivated within 5 s when a single layer was used, whereas their 1D-values were equal to 2-4 s (H. burtonii) and to 3-13 s (P. brevicompactum) when a multilayer was tested. Given the low fungal contamination of food packaging devices and the possibility of developing tailored LED systems, UV-C LED technology was confirmed as an interesting method of sanitization for food packaging. Industrial relevance: This study provides data on the behaviour of two different UV-C LED systems in inactivating fungal conidia on polyethylene terephthalate surfaces. This study helps to understand how specific factors (e.g., spatial arrangement of cells; fluctuating fungal loads on packaging devices) can influence the UV-C LED system performance and therefore could be useful for both plant manufacturers and food industries to develop tailored UV-C LED systems.