The Effect of Essential Oils on Foodborne Pathogens in Leafy Vegetables

Prepared vegetables mixes are one of the most promising developments in the fresh-cut food industry. The aim of this study was to investigate the ability of Origanum compactum (oregano), Eugenia caryophyllus (clove), and Zataria multiflora Boiss (zataria) essential oils (EOs) to control the growth of potentially cross contaminating pathogens and endogenous microbiota in commercial vegetable leaves, processed in a fresh-cut produce company. After the sanitizing washing step, 25 grams of vegetables were packed in strile poly-ethylen bags and sprayed by various concentrations (3, 5 and 10 percent) of emulsions of EOs (0.8 ml). Zataria EO emulsions of 3 percent, 5 percent and 10 percent reduced Escherichia coli O157:H7 by 1.7, 2.2 and 3.5 log cfu/g in vegetables after 5 days of storage at 7 °C. By contrast, reductions in E. coli O157:H7 counts remained the same when clove was applied at concentrations of 5 percent and 10 percent (2.5 log cfu/g reduction). Oregano (10 percent) reduced inoculated E. coli O157:H7 counts in vegetables by a maximum of 0.5 log cfu/g after 5 days of storage at 7 °C. Zataria showed strong antimicrobial efficacy against E. coli O157:H7 and also against the endogenous microbiota of vegetables stored for 9 days. Feline calicivirus (FCV), anorovirus surrogate, survived on inoculated vegetables during refrigerated storage (9 days at 7 °C) regardless of treatment. Refrigeration temperatures completely annulled the effectiveness of the EOs against FCV. This study shows that EOs, and zataria in particular, have great potential use as an additional barrier to reduce contaminationrelated risks in salads.