Antimicrobial Efficacy of Eugenol and Neem Oil Nanoemulsions Against Foodborne Pathogens and Food Spoilage Fungi

Abstract

Essential oils are widely recognized for their antimicrobial properties, making them promising natural alternatives for food preservation and spoilage prevention. However, practical challenges such as hydrophobicity, instability, and strong aroma have limited their applications. To overcome these challenges, this study aimed to prepare nanoemulsions of eugenol and neem oil using ultrasonication techniques and evaluating their antimicrobial efficacy, highlighting their potential for sustainable food preservation. The antimicrobial efficacy of these nanoemulsions was evaluated against four foodborne bacteria and spoilage fungi using well diffusion method. Nanoemulsions, formulated with oil concentrations of 5%–20%, exhibited particle sizes ranging from 135 to 373 d.nm for neem oil and 410 to 587 d.nm for eugenol, with polydispersity indices indicating variable size distribution (0.27–0.88 for neem oil and 0.13–0.60 for eugenol). Stability tests confirmed overall stability, although some eugenol-based nanoemulsions exhibited minor precipitation due to turbidity. Both neem oil and eugenol nanoemulsions displayed significant antimicrobial activity, with eugenol being more effective even at lower concentrations. NNE-20 showed the largest inhibition zones against Bacillus subtilis (17.83 mm), Escherichia coli (14.83 mm), and Enterobacter aerogenes (14.16 mm), while NNE-15 was most effective against Staphylococcus aureus (14 mm). Eugenol nanoemulsions exhibited superior antibacterial activity, achieving inhibition zones of 18–23.5 mm with higher eugenol concentrations. For fungi, neem oil nanoemulsions inhibited Colletotrichum gloeosporioides, Rhizopus stolonifer and Aspergillus niger (15–20 mm), while eugenol nanoemulsions outperformed neem oil, showing zones of 24–26 mm (Aspergillus niger) and 20–24 mm (Saccharomyces cerevisiae). These findings highlight the potential of neem oil and eugenol nanoemulsions as stable, natural, and effective alternatives to synthetic preservatives for improving food safety and extending shelf life.

Keywords

antibacterial activity, natural food preservative / essential oil / functional agent / nanoemulsion

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2025 The Author(s). Food Bioengineering published by John Wiley & Sons Australia, Ltd on behalf of State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology.