Improving Anti-listeria Activity of Thymol Emulsions by Adding Lauric Acid

In this study, a novel emulsion, thymol (Thy) and lauric acid (LA) emulsion (Thy/LA-Emulsion) was prepared by homogenizing eutectic solvent (Thy/LA mixture) and caseinate solution. The effects of different thymol and lauric acid mass ratio on the formation, stability, and antibacterial activity of emulsions were studied. Compared with thymol alone, adding lauric acid (25, 50, and 75%) could enhance the antibacterial efficacy of the emulsions. Among them, Thy/LA_25%-Emulsion could be stored at room temperature for a month without the increase of particle size, indicating that the addition of LA had not impacted the stability of emulsions. Meanwhile, Thy/LA_25%-Emulsion exhibited a greater inhibition zone (3.06 ± 0.12 cm) and required a lower concentration (0.125 mg/mL) to completely inhibit the growth of Listeria monocytogenes. Consequently, Thy/LA_25%-Emulsion demonstrated the best antibacterial activity and physicochemical stability due to its long-term storage stability. Our results suggest that Thy/LA_25%-Emulsion may become a more functional natural antibacterial agent with greater commercial potential owing to its cheaper raw materials, simpler production processes, and better antibacterial effect in the food industry.