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Introduction: The hydrophobicity, strong flavor and high volatility of essential oils impede their commercial application in foods. Purpose: To study the encapsulation of Oregano essential oil (OEO) in β-cyclodextrin (β-CD) and lipidic dispersions to enhance dispersion and controlled release of OEO and evaluate their effect on the survival of Listeria monocytogenes in Tryptic Soy Broth (TSB) and cheese broth. Methods: The encapsulation of OEO in β-CD was performed with the co-precipitation method, whereas for the incorporation of OEO into lipidic dispersion the thin-film hydration method was applied. Size distribution (PDI) and zeta-potential(ζ) of the formed inclusion complexes (IC) were assessed by Dynamic Light Scattering (DLS). Determination of encapsulation efficiency (EE%) and release rate of the formed ICs was performed by UV-Vis spectroscopy. The effect of ICs and free OEO at MIC, ½ MIC and 2xMIC against L. monocytogenes (3-strain cocktail: 106 CFU/ml), was determined in TSB (pH 7.0, 4.3) and "katiki" cheese broth (pH 4.3) at 7o C. Results: The complexes presented nanoscale size (90% for OEO-β-CD and 106.84 ±42.81 and 948.05 ±409.95nm with intensity of 47% and 51.9%, respectively for OEO-lipidic dispersion. The size dispersion was 0.433 ±0.064 nm for OEO-β-CD and 0.872 ±0.070 nm for OEO-lipidic dispersion. An acceptable stability was observed (>20 mV) with ζ-potential -23.57±6.76 mV for OEO-β-CD and -49.5±6.18 mV for lipidic dispersion. EE% was 80.3%±4.0 and 87.8±3.7 for OEO-β-CD and OEO lipidic dispersion, respectively. The OEO release from both complexes occurred continuously for 18 days. The dose-dependent inhibitory effect of encapsulated OEO against L. monocytogenes was higher in TSB than in cheese-broth and increased at lower pH. Lipidic dispersion was more effective than OEO-β-CD at both pH values. The antimicrobial effect of encapsulated OEO was not as rapid as the effect of free EO, confirming the slow release of EO due to encapsulation. Significance: The results are indicative for the application of encapsulated OEO to control of L. monocytogenes in foods. |
