Design of biosystems to provide healthy and safe food. Part A: effect of emulsifier and preparation technique on physicochemical, antioxidant and antimicrobial properties
Résumé
In this study, the effect of emulsifier and preparation technique on physicochemical properties and antioxidant/antimicrobial activity of plant oil (lemongrass and oregano, 1:1)/citrus extracts incorporated in oil-in-water (O/W) microemulsion in comparison to coarse emulsion, was investigated. The optimization of O/W microemulsion was performed by two surfactants with different hydrophilic–lipophilic balance values and two techniques of preparation such as sonication and microfluidization. The stability of microemulsions during storage time regarding to the droplet size, ζ-potential, viscosity, total polyphenolics content, total flavonoids content, antioxidant, antiradical and antimicrobial activity were assessed. Micro-emulsification increased the bioactivity of plant oil/citrus extracts by increasing the surface area of droplets induced by size decrement. Microfluidized and sonicated emulsions showed the same relatively stable profile during storage time. Micro-emulsification improves the functionality of plant oil/citrus extracts, such as antioxidant and antiradical activity. An increment about 16–32 times in antimicrobial activity of plant oil/citrus extracts was also attained. Furthermore, the morphology of microemulsions observed by transmission electron microscopy, confirmed a mono-dispersed nano-sized emulsion.