Effect of Type of Water, Concentration, and Freshness of Peroxyacetic Acid Solutions against Different Microbial Cultures and <i>Salmonella</i> Strains of Concern for Poultry

Relatively stable peroxyacetic acid (PAA) concentrates (23% PAA) are diluted with tap water for industrial biocidal application. The biocidal effectiveness of PAA solutions depending on storage at room temperature, type of water used for dilution, effect of concentration, and contact time, against different microbial cultures and three Salmonella strains enforced by FSIS to be eliminated for commercial distribution of raw poultry carcasses, was evaluated in this study. PAA is very reactive and quickly decomposes to acetic acid, oxygen, and water. At room temperature (20 °C), the biocidal activity of PAA is reduced significantly (up to 50%) after 24 h of being diluted for application. Increasing PAA (at 250 ppm in distilled water) contact time from 15 to 30 s increased the microbial reduction against a shrimp-derived microbial culture for at least one log cycle. PAA effectiveness varied depending on the source of microbial culture, being more effective on mixed microbial cultures from marine products than on those from poultry. Also, PAA is more powerful when dissolved in tap water than in Brita-filtered and distilled water, likely related to dissolved chemicals that promote reactions of hydrogen peroxide in PAA with generation of oxygen radicals and subsequent oxidation and microbial cell damage. Increasing the PAA concentration in tap water increases the microbial log reduction of chicken culture and Salmonella in a logarithmic pattern. While PAA at 500 ppm in tap water reached a 5-log reduction of mixed microbial culture sourced from chicken skin, only 125 ppm PAA in tap water is required to achieve the same log reduction in S. enteritidis, the most resistant Salmonella of concern for poultry carcass sanitation for commercial trade. It is concluded that PAA freshly dissolved in tap water is an effective biocide at 15 s contact time capable of achieving a 5-log microbial reduction on a chicken-derived microbial culture when used at 500 ppm, and it is even more effective to achieve this level of microbial reduction, at 125 ppm, against pathogenic Salmonella strains.