Annals. Food Science and Technology 2018 Available on-line at www.afst.valahia.ro 324 Volume 19, Issue 2, 2018 EFFECTIVENESS OF CHEMICAL WASH INTERVENTIONS FOR KILLING SALMONELLA ENTERICA AND ESCHERICHIA COLI O157:H7 ON PARSLEY AND GREEN ONIONS Aubrey Mendonça 1* , Aura Daraba 2 , James Drummer 3 , Fei Wang 1 1 Department of Food Science & Human Nutrition, Iowa State University, Ames, IA 50011 2 Department of Food Science, Food Engineering & Applied Biotechnology University “Dunarea de Jos” of Galati, Romania 3 George Washington Carver Scholar, Iowa State University * E-mail: amendon@iastate.edu 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. Key words: leafy greens, chlorine, PRO-SAN, decontamination, E. coli O157:H7 and S. enterica Received: 29.03.2017 Reviewed: 16.05.2018 Accepted: 06.06.2018 1. INTRODUCTION Pathogens can contaminate leafy greens during any point of the farm-to-table chain, from production, harvesting, postharvest handling, fresh-cut or value-added operations to distribution and end-user handling. Also, the leafy greens growers recognize that once their produces are contaminated, removal or killing the pathogens is difficult and prevention of microbial contamination at all steps from production to distribution is strongly favored but not always possible. There are many on- farm factors such as the presence of wild animals, birds and insects, soil amendments and irrigation waters can carry human pathogens (Söderqvist, 2017; Pachepsky et al., 2011) which can make almost impossible to avoid on the field contamination of leafy produces. Other sources of contamination include field workers, lack of on-farm hand- washing and sanitizing facilities, and the equipment used during harvest and transport to the processing plant (Beuchat, 2006). Because of fewer known effective food safety interventions that can be applied during pre- harvest of leafy greens, Good Agricultural Practices (GAPs) are put in place and focus on water management, testing soil amendments, manure management, sanitation practices, wildlife and pest control, and worker training and hygiene during pre-harvest production (Food and Drug Administration, 1998). The success of GAPs in preventing cross- contamination of and ensuring the safety of the produce is not always achieved and studies have shown that growers do not always follow GAPs on their farms (Ellis et al, 2005; Rodrigues et al., 2014; Kovacs and Davis, 2014) with negative consequences on the safety