Inactivation of foodborne pathogens (Salmonella and Listeria monocytogenes) on locally processed spinaches by three-step wash with antimicrobials

Three-step wash with commercial antimicrobials including a H2O2-peroxyacetic-acid mixer, chlorine water and a lactic/citric acid blend was conducted to inactivate foodborne pathogens on spinaches. Fresh spinaches from West Virginia small growers were artificially contaminated with a 4-strain mixture of Salmonella and Listeria monocytogenes. Inoculated spinaches were three-step washed in water, antimicrobial, and water (WAW) or in water, water, and antimicrobial (WWA) with 10 s of each step. Antimicrobial treatments are sodium hypochlorite (SH; 100 ppm, pH-6.8), lactic/citric acid blend (LCA; 2.5%), and a H2O2-peroxyacetic-acid mixer (SaniDate-5.0, 0.0064, 0.25 and 0.50%). Microbial populations were analyzed on XLT-4 (Salmonella) and MOX agars (L. monocytogenes) with a total of 9 samples (3 replicates) followed by analyzed using SAS (Mixed Model Procedure, P < 0.05). Unwashed spinaches recovered 4.57-5.10 and 6.68-6.73 log(10) CFU/g of Salmonella and L. monocytogenes, respectively. WWA procedure obtained additional reductions of the pathogens by 0.35-1.07 log(10) CFU/g (LsMeans) than the WAW procedure. Three-step wash in 0.25% and 0.50% of SaniDate-5.0 solution showed at least similar or even greater (P < 0.05) reductions of the pathogens on spinaches than those of SH and LCA treated samples. Results suggested that SaniDate-5.0 is a promising antimicrobial agent that could be suggested to WV small spinach growers during post-harvest three-step wash process.