Physicochemical properties and antibacterial activity of hydrophobic deep eutectic solvent-in-water nanoemulsion

In this study, hydrophobic deep eutectic solvent (HDES)-in-water nanoemulsions were prepared as potential antimicrobial delivery systems. Firstly, HDESs based on the eutectic mixing of binary natural antimicrobial including medium-chain fatty acids (caprylic acid, capric acid, or lauric acid) and terpenoids (menthol or thymol) were prepared, and their physicochemical properties were studied. Then HDES-in-water nanoemulsion stabilized by a food-grade non-ionic surfactant (Tween 80) was successfully prepared by ultrasonic treatment. Results showed that HDES components have a significant impact on the physicochemical properties of HDESs, such as surface tension, viscosity, and melting point, to affect the mean particle diameter and zeta-potential of the corresponding emulsions. Except for emulsions formed by thymol-based HDES, the mean particle diameter of the emulsions are normally < 100 nm. Besides, both emulsion stability and antimicrobial activity of the nanoemulsions against two foodborne pathogens (Escherichia coli, Staphylococcus aureus) were evaluated. It was found that the nanoemulsion maintained excellent performances in storage, thermal, and pH stability. The antibacterial effect is affected by differernt type of bacteria, emulsified form, and HDES compositions. This work represents the starting point for future applications of HDESs with antibacterial properties in food and other industries. (C) 2021 Elsevier B.V. All rights reserved.