Abstract

The effectiveness of selected antimicrobial solutions for killing Salmonella enterica and Escherichia coli O157:H7 on artificially inoculated parsley and green onions has been tested. Samples (25 g) of green onions and parsley were artificially inoculated with a 5 strain-cocktail of each pathogen and held at 23 ± 1 °C (16 to 18 hours) before immersing them (2 minutes) in: sterile distilled water (H2O), chlorine (CHL; 150ppm), 1% (vol/vol) PRO-SAN (PRO1), or 2% (vol/vol) PRO-SAN (PRO2). Subsequently, the vegetables were rinsed in distilled water (3 seconds) to remove residual antimicrobials. Inoculated vegetables, but not immersed in antimicrobial solutions, served as control. Samples were transferred into a stomacher bag containing 50 ml of sterile 0.1% (w/v) peptone water. Aliquots (0.1 ml) of peptone wash solution were surface-plated on xylose lysine tergitol 4 agar or sorbitol MacConkey agar containing nalidixic acid (50 μg/ml) for counting viable S. enterica and E. coli O157:H7, respectively. Following incubation at 35 ⁰C for 48 h the bacterial colonies were counted. Immersion of inoculated parsley in water alone reduced initial numbers of E. coli O157:H7 and S. enterica by 1.3 and 1.07 log, respectively. Log reductions on green onions immersed in water were 0.43 (E. coli O157:H7) and 0.58 (S. enterica). Both CHL and PRO1 reduced initial numbers of the pathogens by approximately 2.5 log. The PRO2 solution killed more than 5.0 log of each pathogen on the leafy greens.

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