Antimicrobial activity of orange essential oil (Citrus sinensis) against foodborne and zoonotic bacterial strains

Authors: Manuela Oliveira, Luiz Quintella, Raquel Abreu, Susana Alves, Luís Tavares, and Eva Cunha

Ger. J. Microbiol. 2026. vol. 6, Iss. 3 pp:59-68
Doi: https://doi.org/10.51585/gjm.2026.3.0070

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Abstract:

Orange essential oil (OEO), a by-product of the orange processing industry, is attracting increasing interest as a sustainable source of bioactive compounds with applications in the food, pharmaceutical, and cosmetic sectors, owing to its aromatic, antioxidant, and antimicrobial properties. In this study, after characterizing the chemical composition of the Citrus sinensis OEO by gas chromatography coupled with mass spectrometry, its antimicrobial activity was evaluated against a panel of bacterial strains of high relevance to food safety and public health. These included the reference strains Staphylococcus aureus ATCC 25923, Listeria monocytogenes CECT 935, Escherichia coli ATCC 25922, three Salmonella enterica strains (CECT 443, CECT 722, and CECT 7162), and two clinical isolates from swine, L. monocytogenes E1 and S. enterica 104, representing potential zoonotic transmission routes within the food chain. Antimicrobial activity was initially assessed using the disk diffusion method, followed by broth microdilution to determine the Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) of the OEO. Limonene was identified as the major component of OEO, accounting for 69% of the total oil composition. The OEO exhibited antimicrobial activity against S. aureus, both L. monocytogenes strains, and S. enterica CECT 443 in disk diffusion assays. OEO MIC values were 8 µL/mL for S. aureus, 125 µL/mL for both L. monocytogenes strains, and 63 µL/mL for S. enterica CECT 443. The MBC was 125 µL/mL for all susceptible strains. These results highlight the antimicrobial potential of OEO, particularly against Gram-positive pathogens and selected Salmonella strains, including isolates relevant to public health. Limonene-rich OEO emerges as a promising natural antimicrobial agent, supporting its potential use as a food preservative. Further studies are needed to assess its efficacy under food processing and storage conditions.

Keywords:

Orange Essential Oil, Antimicrobial activity, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella enterica

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