Integrated Impedometric Approach for Screening Natural Preservatives Against Food-Related Microorganisms

The growing demand for natural and sustainable preservatives has renewed interest in essential oils (EOs) because of their potential antimicrobial and antioxidant activities. In this study, lemon, lavender, and oregano EOs, together with tomato and artichoke extracts, were evaluated against foodborne and spoilage microorganisms using an impedometric approach. Three bacterial strains (Listeria innocua, Escherichia coli, and Pseudomonas fluorescens) and two yeast strains (Zygosaccharomyces bailii and Kluyveromyces marxianus) were tested. Tomato and artichoke extracts showed no antimicrobial activity under the tested conditions, with MIC values higher than 66.67 µL/mL. Among the EOs, oregano EO showed the strongest antimicrobial properties, with both bacteriostatic and bactericidal effects, even at low concentrations for all tested strains. In contrast, lavender EO was the most effective against yeast, with MIC and MFC values of 0.75 µL/mL for both species. Antioxidant activity, assessed via DPPH and Oxitest assays, was highest for oregano EO, which showed a 95% total antioxidant capacity and an induction period of 1224 min. Overall, the results support the use of impedance-based methods as a rapid and informative tool for screening natural preservatives and identify oregano EO as the most promising multifunctional candidate, combining strong antibacterial and antioxidant properties.