Physical and antimicrobial properties of thyme oil emulsions stabilized by ovalbumin and gum arabic

• The bilayer and complexes emulsions remained stable after long storage period.
• The oil phase had an appreciable effect on size and retention of the TO emulsions.
• The TO emulsion showed a longer-term antimicrobial activity compared to pure TO.
• The complexes emulsion had more antimicrobial activity than the bilayer at pH 4.0.
• The OVA/GA complexes could control the release properties of TO.

Natural biopolymer stabilized oil-in-water emulsions were formulated using ovalbumin (OVA), gum arabic (GA) solutions and their complexes. The influence of interfacial structure of emulsion (OVA-GA bilayer and OVA/GA complexes emulsions) on the physical properties and antimicrobial activity of thyme oil (TO) emulsion against Escherichia coli (E. coli) was evaluated. The results revealed that the two types of emulsions with different oil phase compositions remained stable during a long storage period. The oil phase composition had an appreciable influence on the mean particle diameter and retention of the TO emulsions. The stable emulsion showed a higher minimum inhibitory concentration (MIC), and the TO emulsions showed an improved long-term antimicrobial activity compared to the pure thyme oil, especially complexes emulsion at pH 4.0. These results provided useful information for developing protection and delivery systems for essential oil using biopolymer.