Inhibition of bacterial human pathogens on tomato skin surfaces using eugenol‐loaded surfactant micelles during refrigerated and abuse storage

Abstract

The plant‐derived essential oil component eugenol (1.0% wt/vol), free or loaded into surfactant micelles constructed of sodium dodecyl sulfate (SDS; 1.0% wt/vol), 200 ppm free chlorine (hypochlorous acid [HOCl]; pH 7.0), and sterile distilled water were evaluated for their ability to reduce Salmonella Saintpaul and Escherichia coli O157:H7 on skin surface samples of Roma tomatoes. Samples were treated and then stored aerobically for up to 10 days. All samples were initially stored at 5 °C; one set of samples was shifted to 15 °C after 5 days of storage to simulate temperature abuse during postharvest handling. Encapsulated and free eugenol, HOCl, and empty SDS micelles reduced pathogens to nondetectable counts (detection limit: 0.5 log10 cfu/cm2) during refrigerated storage (p ≥ .05). Conversely, during temperature abuse storage (15 °C), only free and micelle‐loaded eugenol consistently reduced pathogens to nondetection. Eugenol‐loaded micelles can be used to decontaminate harvested tomatoes from enteric bacterial pathogens. Practical applications Tomatoes may be consumed raw and have been repeatedly implicated in the occurrence of human foodborne disease. Washing of tomatoes with novel antimicrobial interventions that increase the dispersion of antimicrobials over the surface of the tomato should result in greater reduction of microbial foodborne pathogens through enhanced contact of antimicrobial with pathogen. Application of surfactant micelle‐entrapped eugenol onto tomato surfaces reduced Salmonella Saintpaul and Escherichia coli O157:H7 to nondetection during refrigerated (5 °C) and temperature abuse (15 °C) storage. Micelle‐loaded eugenol reduced numbers of aerobic bacteria, Enterobacteriaceae, and fungi to nondetection during temperature abuse storage.

Antimicrobial-Loaded Polymeric Micelles Inhibit Enteric Bacterial Pathogens on Spinach Leaf Surfaces During Multiple Simulated Pathogen Contamination Events

“…Plant-derived antimicrobials (PDAs) make attractive produce disinfectants due to their natural origin, compatibility with various produce commodities, and utility against microbial pathogens (Yoon and Lee, 2018). Nonetheless, PDA utility is often limited due to inherent volatility and, in some instances, low water solubility (Ruengvisesh et al, 2019b). One strategy to overcome these limitations of PDAs is to encapsulate them in a water-miscible system to facilitate their delivery to produce surfaces, potentially improving on observed antimicrobial effects (Yegin et al, 2016).…”

Inhibition of Escherichia coli O157:H7 and Salmonella enterica Isolates on Spinach Leaf Surfaces Using Eugenol-Loaded Surfactant Micelles

“…Kang et al [22] showed that cinnamon leaf essential oil in cetylpyridinium chloride produced 1.8 and 1.5 log 10 CFU/g reductions against L. monocytogenes and E. coli O157:H7, respectively; quality of kale leaves was not affected during storage. In our previous study, eugenol (1% w/v ) encapsulated in SDS (1% w/v ) micelles were used for inhibition of S. Saintpaul and E. coli O157:H7 as well as native microbiota on tomato skin surfaces during refrigerated and abuse storage [28]. In that study, antimicrobial effects of free and encapsulated eugenol did not differ from those of HOCl and empty SDS micelles during refrigerated storage.…”

“…In that study, antimicrobial effects of free and encapsulated eugenol did not differ from those of HOCl and empty SDS micelles during refrigerated storage. However, reductions in pathogen counts to non-detectable levels were only observed with free and encapsulated eugenol [28]. EOC-encapsulated micelles could be used as an alternative to the commonly used sanitizers to reduce pathogens on fresh produce, potentially achieving greater pathogen reductions versus those typically observed by washing in chlorinated water [60].…”

“…Eugenol-loaded micelles and other treatments (free eugenol, empty micelles, 200 ppm free chlorine, sterile distilled water) were prepared in identical manner to methods reported previously by our group [28]. Briefly, eugenol stock solution (70% w/v ) was prepared by dissolution of eugenol (Sigma-Aldrich Co., St. Louis, MO, USA) in 95% ethyl alcohol (Koptec, King of Prussia, PA, USA), and stored at 5 °C until ready for use.…”

Impacts of Clarification Techniques on Sample Constituents and Pathogen Retention

“…To provide a framework for the deductive selection of an effective sample preparation technique, particle size, composition and bacterial retention both pre-and post-implementation were analyzed for several sample preparation methods including continuous flow centrifugation, glass wool, graphite felt, and 50 µm polypropylene filters. Although there is concern regarding the ability of bacteria to bind to matrix components [40][41][42][43], the study herein did not attempt to incorporate a "release agent" [44][45][46][47][48] and simply added the inoculum to the matrix without an incubation step to lessen the likelihood of bacteria/ matrix interactions and avoid confounding the analysis. However, we acknowledge this concern and recognize that addition of any such agent may alter the effects of the clarification processes presented here.…”