Effectiveness of air disinfection by ozonation or hydrogen peroxide aerosolization in dairy environments

Indoor air of dairy industry acts as a source or vehicle of microbial contamination affecting both food safety and product shelf life. This research focused on both the monitoring of the air microbial load in selected areas of a dairy factory and in evaluating the effect of air disinfection through ozonation or chemical aerosolization by hydrogen peroxide. The air microbial load was weekly monitored in the autumn/winter season after the routinely applied sanitation procedures. Air samplings, through impaction method, were carried out in 3 critical areas (cheese making, storage and packaging). Total bacteria, moulds and yeasts resulted in mean counts of 161 (±154) MPN m-3, 228 (±234) MPN m-3, and 137 (±439) MPN m-3, respectively. The dairy location exhibiting the lowest contamination was the storage cell. A large variability of microbial loads characterized the packaging area. Mycobiota pattern consisted in 11 species of moulds isolated and identified through mycological and molecular techniques. The isolates observed in the indoor air mainly consisted of Cladosporium spp., Alternaria spp., and Penicillium spp.. The yeast community was mainly represented by Cryptococcus spp., Debaryomyces spp., Bulleromyces spp., and Sporobolomyces spp.. Both ozonation and hydrogen peroxide aerosolization were effective techniques in the inactivation of airborne microorganisms. After air treatment only residual fungi were identified. We verified that their occurrence was promoted by environmental recontamination.