Antimicrobial effects of eugenol-based micro- vs. nano-emulsions: Evaluation of shelf-life enhancement in Sikhye

This study investigated the antibacterial properties of micro-emulsions (MEs) and nano-emulsions (NEs) containing eugenol and rice bran oil to enhance the shelf life of Sikhye, a traditional Korean rice beverage. The emulsions were evaluated using the agar disk diffusion method and minimum inhibitory concentration (MIC) tests against Escherichia coli, Bacillus cereus, and Staphylococcus aureus. The results demonstrated that MEs exhibited larger inhibition zones and lower MIC values than NEs, indicating superior antibacterial activity. The application of these emulsions in Sikhye revealed that a higher eugenol content and larger droplet size effectively inhibited bacterial growth. The study also found that, while rice bran oil contributed to physical stability, it did not enhance the antimicrobial effect and, in some cases, promoted bacterial growth. Overall, these findings suggest that eugenol-rich MEs could serve as effective natural preservatives, improving the safety and shelf life of Sikhye and potentially other food products.