Inactivation of Aspergillus brasiliensis ATCC 16404 conidia by biocides and UV irradiation alone and in combination

Fungal contamination is a major concern in the food production chain, particularly in the dairy industry. Traditional cleaning and disinfection techniques, though effective, can produce undesirable by-products (e.g. chloramines) and may not comply with increasing consumers' demands for natural, non-toxic, and environmentally friendly solutions. This study explores the efficacy of biocides (ethanol, peracetic acid, acetic acid) and UV irradiation, alone and in combination, for different duration and intensities. Aspergillus brasiliensis ATCC 16404 was used as it is a reference strain in disinfection evaluation standards. Unlike many previous studies solely based on hydrated conidia, dry conidia were also tested to mimic airborne conidia that are responsible for contamination. Dry conidia were more sensitive to UV than the hydrated ones, but their aggregation could significantly reduce UV efficiency. Overall, these conidia exhibited higher sensitivity to alcohol-based biocides. Finally, the effect of combination treatments was assessed using biocides containing less than 1% active compounds and short times (1 to 5 min) UV irradiations to allow survivors after each treatment. A synergistic effect, ranging from 1.33 to 3.93 log additional reduction, was obtained when an acid-based disinfectant was used sequentially with UV for both hydrated and dry conidia, thus achieving more than 4 log reductions.