Evaluation of antibacterial effect of Rosmarinus officinalis L. essential oil on three food-borne pathogens in vegetables by propidium monoazide quantitative PCR

Essential oils (EOs) have long been applied as flavoring agents in foods. Nowadays, due to the antimicrobial properties of EOs, they have been used as natural food preservatives. In this study, initial experiments were performed in order to elucidate the minimum bactericidal concentration of Rosmarinus officinalis L.EO on Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes. Thereafter, PMA-qPCR was applied in order to selectively quantify living cells within a bacterial population treated with rosemary EO. Inactivation was obtained at EO concentrations of 1%, 0.45%, 0.9% for L. monocytogenes, E. coli O157:H7 and S. enterica, respectively. L. monocytogenes were totally killed within 45 min while it took 90 min for E. coli O157:H7and S. enterica. It was concluded that rosemary EO has the potential to be used as a natural food additive or bio-preservative since it was able to irreversibly inactivate the three tested pathogens at lower concentrations and short exposition times in comparison with the other EOs. In addition, PMA-qPCR approach proved quantitatively precise and specific to selectively detect live pathogenic bacteria in vegetables following inactivation with rosemary EO

The Effect of Essential Oils on Foodborne Pathogens in Leafy Vegetables

Background and Aims 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. Materials and Methods 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). Results 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. Conclusion This study shows that EOs, and zataria in particular, have great potential use as an additional barrier to reduce contaminationrelated risks in salads. * Corresponding Author: Amol University of Special Modern Technologies, Faculty of Veterinary Medicine. E-mail: [email protected]

Molecular identification of lactic acid bacteria associated with chicha, a traditional maize-based fermented beverage from Northwestern Argentina

Chicha is a traditionally homemade fermented alcoholic beverage prepared from maize in the Andean highlands. Here the dominant lactic acid bacteria (LAB) species present during chicha production in Northwestern Argentina were analyzed by molecular methods. Examination of these indigenous foods may provide information on unknown microbial genetic reservoirs which can be exploited as new functional starter cultures to improve nutritional and functional quality of traditional Andean food