Purpose: This study investigated the effectiveness of PRO-SAN compared to that of chlorine for killing Salmonella enterica and Escherichia coli O157:H7 on parsley and green onions.
Methods: Each vegetable (25 g) was inoculated with 5 strains of nalidixic acid resistant S. enterica or E. coli O157:H7 and held at 23 ± 1°C for 16 to 18 hours. The vegetables were subsequently immersed (2 min) in: distilled water (H2O), chlorine (CHL; 150 ppm), 1% (vol/vol) PRO-SAN (PRO1) or 2% (vol/vol) PRO-SAN (PRO2). Samples that were not immersed in solutions served as controls. The immersed vegetables were rinsed (3 s) in distilled water and then pummeled in a stomacher bag containing 50 ml of sterile 0.1% (w/v) peptone. Aliquots (0.1 ml) of peptone wash solution were surface-plated on xylose lysine tergitol 4 agar or sorbitol MacConkey agar each containing nalidixic acid (50 µg/ml). The agar plates were incubated at 35°C and bacterial colonies were counted after 48 h.
Results: Immersion of parsley in water reduced E. coli and S. enterica by 1.30 and 1.07 log, respectively. Log reductions of pathogens on green onions, immersed in water, were 0.43 (E. coli) and 0.58 (S. enterica). CHL and PRO1 reduced initial numbers of the pathogens by approximately 2.5 log. PRO2 [2% (vol/vol)] consistently killed more than 5.0 log of each pathogen (P < 0.05). These results demonstrate the effectiveness PRO2 for killing S. enterica or E. coli O157:H7 on parsley and green onions.
Significance: The results indicate that the PRO-SAN (2%) has good potential to replace chlorine solution (150 ppm) for killing enteric pathogens on parsley and green onions.