Protective Effect of Eucalyptus radiata Essential Oil-Based Nanoemulsion Against Pathogenic Bacteria and Spoilage...

The antimicrobial effect of Eucalyptus radiata essential oil nanoemulsion (EON) on Staphylococcus aureus and spoilage microorganisms was evaluated on fresh beef chunks during cold storage at days 0, 2, 4, 6, and 8. For this purpose, nanoemulsion was prepared using 2% eucalyptus oil combined with high methoxyl pectin, glycerol, and Tween 80, employing high shear force. Then the following were evaluated: (1) the essential oil's chemical profile and in vitro antioxidant and antimicrobial capacities; (2) the nanoemulsion characteristics; and (3) the microbial counts of the beef treatments. The results showed that the essential oil's primary components were o-cymene (45.4%), 2-bornene (26.29%), 1,8-cineole (11.31%), and α-pinene (9.25%). The EON had a particle size of 52.04 nm and a zeta potential of -9.16 mV. The in vitro studies revealed that both the essential oil and its nanoemulsion demonstrated significant antibacterial activity. Similarly, in in situ examinations, when the meat samples were spiked with S. aureus (0.1 × 10⁸ CFU/mL), the EON-treated meat samples had significantly (p ≤ 0.05) lower microbial counts than the untreated meat samples throughout the storage period; the difference between the treatments ranged between 1.62 and 2.44 log CFU/g. Additionally, the EON exhibited excellent antimicrobial efficacy against spoilage microorganisms on beef pieces during shelf life. On day 4, the maximum inhibitory activity was observed against total coliform, Pseudomonas spp., and yeast in reductions of 1.96, 2.09, and 2.18 log CFU/g in microbial counts, respectively. Moreover, application of meat samples with the EON delayed spoilage by 4 days. Therefore, the results of this study showed that coating beef chunks with the EON enhanced both product safety and shelf life.