Oregano and Thyme Essential Oils Encapsulated in Chitosan Nanoparticles as Effective Antimicrobial Agents against Foodborne Pathogens

Abstract

The use of natural compounds with biocidal activity to fight the growth of bacteria responsible for foodborne illness is one of the main research challenges in the food sector. This study reports the preparation and physicochemical characterization of chitosan nanoparticles loaded with Thymus capitatus (Th-CNPs) and Origanum vulgare (Or-CNPs) essential oils. The nanosystems were obtained by ionotropic gelation technique with high encapsulation efficiency (80–83%) and loading capacity (26–27%). Nanoparticles showed a spherical shape, bimodal particle size distribution, and good stability (zeta potential values > 40 mV). The treatment of the nanosuspensions at different temperatures (4 and 40 °C) and storage times (7, 15, 21, and 30 days) did not affect their physicochemical parameters and highlights their reservoir ability for essential oils also under stressful conditions. Both Or-CNPs and Th-CNPs exhibited an enhanced bactericidal activity against foodborne pathogens (S. aureus, E. coli, L. monocytogenes) than pure essential oils. These ecofriendly nanosystems could represent a valid alternative to synthetic preservatives and be of interest for health and food safety.

The Influence of Liquid Medium Choice in Determination of Minimum Inhibitory Concentration of Essential Oils against Pathogenic Bacteria

“…In a study by Granata et al [ 12 ], encapsulated oregano (thymol chemotype) and thyme (carvacrol chemotype) EOs were tested on various pathogens. The MIC of L. monocytogenes determined in BHI was significantly lower (0.03 mg/mL) than the MICs of S. aureus and E. coli grown in MHB (0.06 and 0.12 mg/mL, respectively).…”

Nanoparticles—Attractive Carriers of Antimicrobial Essential Oils

“…Or-CNPs demonstrated lowest MIC values (0.03 mg/mL) against L. monocytogenes and S. Aureus and highest MIC value (0.06 mg/mL) against E. coli . The finding suggested usefulness of developed nanoparticles against prevent of foodborne infections [ 160 ]. Song et al fabricated Mandarin essential oil (MEO)-encapsulated chitosan nanoparticles (CSNPs) with high encapsulation efficiency, particle size and zeta potential as 67.32–82.35%, 131.3–161.9 nm, and >30 mV.…”

A Focused Insight into Thyme: Biological, Chemical, and Therapeutic Properties of an Indigenous Mediterranean Herb

“…These include low water solubility, sensitivity to light, moisture, heat, and oxygen, and various chemical and structural instabilities, in addition to the need for clinical data. Recent efforts for the nanoliposomal formulation of thyme essential oil and its encapsulation in chitosan nanoparticles are being attempted and may represent a valid alternative to circumvent some of these challenges in the interest of thyme oil use for antibacterial and food safety purposes [ 107 , 108 ].…”