Antibacterial and antifungal potential of Origanum vulgare L. essential oil for food applications: bio-guided fractionation and microencapsulation in tomato sauce.

Objective: Foodborne illnesses caused by pathogens such as Staphylococcus aureus, Salmonella enterica, and various fungi continue to pose a major global health threat, affecting millions of people every year [1]. As consumer demand for natural preservatives shifts away from synthetic additives, the search for safe and effective alternatives is becoming increasingly urgent. Essential oils from aromatic plants are known to contain bioactive compounds—especially phenolic compounds such as carvacrol and thymol—that exhibit strong antimicrobial activity. However, their practical application in food is limited by factors such as high volatility, poor water solubility, instability, and strong flavors that can affect sensory quality [2]. This study aimed to address these challenges by first screening essential oils from selected aromatic plants and spices for their antibacterial and antifungal activity against common foodborne pathogens. A promising essential oil was then selected and subjected to bio-guided fractionation to identify its main antimicrobial constituents. Finally, its potential as a natural food preservative was evaluated in a tomato sauce model, comparing the performance of both the free and microencapsulated forms under simulated storage conditions. Methods: The essential oils (EOs) and their fractions were chemically characterižed by GC-MS/FID. The antibacterial activity of the free EOs, the EO fractions, and the microencapsulated Origanum vulgare L. essential oil (OEO) were tested in vitro against Staphylococcus aureus and Salmonella enterica serovar Typhimurium using the well diffusion method. The antifungal activity against Penicillium purpurogenum was evaluated using the same and two additional confirmatory methods. Microencapsulation was performed by emulsifying OEO with gum arabic while maintaining a total solids content of 30% (w/w) with 10% EO. The particle sižes of the emulsion and powder were measured by laser light scattering. For the in situ antimicrobial evaluation, commercially available tomato sauce was inoculated with bacteria or fungi and treated with free or microencapsulated EO to a final EO concentration of 0.3% (w/w). The samples were stored at 25°C for 28 days. Antibacterial and antifungal activities were monitored over time by plating on selective media and using the automated TEMPO® fluorescence detection system. The presence of Salmonella was confirmed using the mini-VIDAS® Easy Salmonella protocol. Results: Among the tested essential oils, oregano essential oil showed the highest antimicrobial activity and was selected for further investigation. Bioguided fractionation identified oxygenated fractions as the main contributors to the antibacterial and antifungal activity. In tomato sauce, both the free and microencapsulated forms of oregano essential oil effectively inhibited the growth of Staphylococcus aureus, Salmonella enterica, and Penicillium purpurogenum throughout the storage period. The use of microencapsulation technology enabled up to three times lower concentrations and at the same time improved sensory acceptance by reducing strong odors and flavors. Conclusions: Microencapsulated Origanum vulgare L. essential oil is an effective natural preservative that exhibits strong antimicrobial activity and improved sensory acceptability. Bio-guided fractionation identified oxygenated compounds as key contributors to its efficacy, while its microencapsulated form showed successful application in tomato sauce, indicating its potential for use in various food systems alongside existing preservation strategies.