Electrostatic and garden spraying eugenol and trans-cinnamaldehyde for reducing Salmonella Typhimurium, Listeria monocytogenes, and Enterococcus faecium on cilantro

Abstract

Microgreens, often consumed fresh, are easily contaminated with foodborne pathogens. This study aims to evaluate eugenol and trans-cinnamaldehyde delivered by garden sprayer (GS) or electrostatic sprayer (ES) against Salmonella Typhimurium, Listeria monocytogenes, and Enterococcus faecium on fresh cilantro. Cilantro were inoculated with bacteria followed by spraying with eugenol and trans-cinnamaldehyde (1-3%) using GS or ES for 60 s. Samples were then spread-plated onto tryptic soy agar plus nalidixic acid for S. Typhimurium and L. monocytogenes, and on bile-esculin agar plus nalidixic acid for E. faecium. Eugenol and trans-cinnamaldehyde delivered by GS achieved additional reductions of 1-1.5 log₁₀ CFU/g (P < 0.05) than ES for the three tested microorganisms. GS or ES with 3% of eugenol was the most effective against S. Typhimurium and E. faecium, whereas GS or ES with 2% trans-cinnamaldehyde was the most effective against L. monocytogenes and E. faecium, respectively. The LS-Means of E. faecium reduction from cilantro samples was significantly lower than that of S. Typhimurium (2.04 vs 3.49 log₁₀ CFU/g). However, L. monocytogenes was the most resistant (P < 0.05) of the three bacteria against 2-3% eugenol and trans-cinnamaldehyde using ES. E. faecium could be used as a conservative surrogate for Salmonella for on cilantro samples, but the results do not support the use of E. faecium as a surrogate for L. monocytogenes. Differences of the microbial reductions are mainly due to the delivered volumes differing between GS and ES not the type of sprayers; therefore, the observed differences cannot be attributed solely to the sprayer type.