Sodium alginate emulsion loaded with linalool: Preparation, characterization and antibacterial mechanism against Shigella sonnei

Abstract

This study aimed to prepare sodium alginate-linalool emulsion (SA-LE) to overcome the low solubility of linalool and explore its inhibitory activity against Shigella sonnei. The results indicated that linalool significantly reduced the interfacial tension between SA and oil phase (p < 0.05). Droplet sizes of fresh emulsions were uniform with sizes from 2.54 to 2.58 μm. The ζ-potential was between −23.94 and -25.03 mV, and the viscosity distribution was 973.62 to 981.03 mPa·s at pH 5–8 (near neutral pH) without significant difference. In addition, linalool could be effectively released from SA-LE in accordance with the Peppas-Sahlin model, mainly described by Fickian diffusion. In particular, SA-LE can inhibit S. sonnei with a minimum inhibitory concentration of 3 mL/L, which was lower than free linalool. The mechanism can be described as damaging the membrane structure and inhibiting respiratory metabolism accompanied by oxidative stress based on FESEM, SDH activity, ATP and ROS content. These results suggest that SA is an effective encapsulation strategy to enhance the stability of linalool and its inhibitory effect on S. sonnei at near neutral pH. Moreover, the prepared SA-LE has the potential to be developed as a natural antibacterial agent to address the growing food safety challenges.