Efficacy of Plant-Derived Compounds Against E scherichia coli O157:H7 During Flume-Washing and Storage of Organic Leafy Greens

Abstract

The antimicrobial efficacy of plant-derived compounds (cinnamaldehyde, carvacrol and citral) against Escherichia coli O157:H7 was evaluated during the flume-tank-washing process and subsequent storage of organic leafy greens. Organic baby and mature spinach, and romaine and iceberg lettuce, inoculated with a cocktail of E. coli O157:H7, were washed for 1 or 2 min in 0.1, 0.3 and 0.5% concentrations of the compounds and stored at 4C. Pathogen survivors were enumerated on days 0, 1 and 3. Significant (P < 0.05) reductions in E. coli O157:H7 populations were observed with all three compounds compared with the controls. Carvacrol at 0.5% was most effective on each leafy green, reducing pathogen populations to undetectable levels on day 0. All of the compounds showed better antimicrobial efficacy at higher concentrations and continued this effect during the 3-day storage. Washing the leafy greens for more than 1 min did not significantly affect the E. coli O157:H7 populations. Practical Applications Organic fresh produce is gaining popularity with the consumers, including minimally processed, bagged leafy greens. However, recent outbreaks of foodborne illnesses associated with organic leafy greens have introduced a need to develop better mitigation strategies. Sanitizers are routinely used during flume-washing of leafy greens; however, use of synthetic decontaminants is prohibited for organic fresh produce. Additionally, commonly used sanitizers such as hydrogen peroxide and peroxyacetic acid have not been proven to be as effective against foodborne pathogens. Plant-derived antimicrobials are therefore being considered by the organic fresh produce industry as alternatives to these sanitizers. This study assessed the efficacy of three plant-derived treatments against Escherichia coli O157:H7 on four types of organic leafy greens in flume-tank wash-water. The results from the study indicate that plant-derived compounds can serve as effective natural antimicrobials against E. coli O157:H7 for washing organic leafy greens before they are bagged and shipped for retail.