Purpose: The efficacy of chlorine (NaClO), peroxyacetic acid (PAA), and Safe Zone as antimicrobial water treatments were compared.
Methods: Hass avocados, cantaloupe, melons, and navel oranges were spot inoculated with attenuated and pathogenic Salmonella spp., stored at 15 or 10°C (citrus) for four days postinoculation (DPI), and treated under simulated recirculating wash water conditions. Simultaneously, uninoculated and inoculated fruits (2:1 ratio) were treated for 0.5, 1, 5, and 10 min with either chlorine (NaClO), peroxyacetic acid (PAA), or SafeZone. Quantitative and qualitative assessments for Salmonella were performed before and after disinfection. Lemons, mandarins, and cucumbers were inoculated and treated with SafeZone, only. The target dose before disinfection was five log CFU/avocado, melon and citrus, and six log CFU/cucumber.
Results: Salmonella counts in avocados and oranges treated with SafeZone, PAA, and chlorine declined to 2 to 1.4 log CFU/fruit after one minute, with 60 to 100% positive in chlorine and PAA treated avocados, and 0 to 50% in SafeZone treated avocados and oranges. SafeZone, PAA, and chlorine treated melons resulted in Salmonella reductions of three, four, and five log CFU/melon circle, respectively. In SafeZone treated lemons and mandarins, Salmonella counts declined to the limit of detection after 10 min, with 10% and 73.3% positives, respectively. In SafeZone treated cucumbers, Salmonella reduction of two to four log was observed with intact samples during inoculation; however, almost no decline was detected when damaged or bruised. Cross-contamination was observed in uninoculated avocados treated with chlorine and PAA (5% and 13%), while prevented in SafeZone treated avocados and citrus. Chlorine and PAA treated melons had the highest rates of cross-contamination (77 to 100%); SafeZone decreased these (<16.7%).
Significance: Comparative evaluation demonstrated SafeZone as a practical antimicrobial water treatment, achieving better results than chlorine and PAA.