Inhibitory Activity of Hydrogen Peroxide, Water and Organic Sanitizers against Escherichia coli O157:H7 on Organic Leafy Greens

Introduction: Increased consumption of fresh produce in the past decade has been accompanied with an increase in related foodborne outbreaks. Escherichia coli O157:H7 has often been the cause of these occurrences. Organic leafy greens have also been implicated in foodborne outbreaks in recent years. However, due to the limited number of approved sanitizers for organic produce, it is necessary to derive and test new alternatives. CHICO wash is an organic sanitizer that has been shown to reduce E. coli, Salmonella, and Clostridium botulinum contamination by 7 logs. However, very few sanitizers with an organic make-up have been tested against foodborne pathogens in organic leafy greens.

Purpose: The antimicrobial efficacies of three different organic sanitizers were evaluated on organic leafy greens contaminated with E. coli O157:H7.

Methods: Three organic formulations at various concentrations: C8.C10 and CG100 (at .2 and .4%) and CHICO (C₃H₈I₀C₃O₇ Wash; 5%), along with the controls: positive, hydrogen-peroxide and water, were tested. Organic baby and adult spinach and romaine and iceberg lettuce were inoculated with a cocktail of E. coli O157:H7 strains at 10⁶ CFU/ml. The contaminated greens were washed in each treatment for 1 or 2 minutes, followed by a wash in D/E neutralizing broth. Greens were then bagged and stored at 4°C. Surviving bacterial populations documented on days 0, 1, and 3 of storage.

Results: With the CHICO treatment, both wash times displayed significant reduction (P < 0.05) of E. coli O157:H7 population.  Compared to the positive control, CHICO and hydrogen-peroxide preformed similarly.  Compared to water, CHICO wash reduced the pathogen population by more than 3 logs on Day 0. Both hydrogen-peroxide and CHICO reduced E. coli O157:H7 populations linearly across the sampling period. 

Significance: This study demonstrates the potential antimicrobial effect of organic sanitizers against Escherichia coli O157:H7 strains on organic leafy greens.