Effect of emulsifier hydrophilic-lipophilic balance (HLB) on the release of thyme essential oil from chitosan films

In order to investigate the effects of different hydrophilic-lipophilic balance (HLB) emulsifying agents on the physical properties, structure and release of essential oil in chitosan-essential oil composite films, the diacetyl tartaric acid ester of mono glycerides (DATEM, HLB 8–9.2), Tween 85 (HLB 11), Tween 80 (HLB 15) and Tween 20 (HLB 16.7) were used to prepare composite film. The results showed that the particle size of the essential oil in the film forming solution decreased with the increase of emulsifier HLB value. Fluorescence microscopy and scanning electron microscope reflected that the particle size of thyme essential oil in composite films depended on the type and HLB of emulsifier. The addition of emulsifier also decreased the water vapor permeability and tensile strength of films. However, the physical properties, the release of essential oil from films and antimicrobial activity of films were not closely related to the HLB of emulsifier, which depended on the solvent type, microbial species and the interaction between emulsifier and film matrix. Lower water vapor permeability (compared with the control film), higher elongation at break and antimicrobial activity (E.coli) were found in Tween 85 composite films, which could be optimal choice to produce active chitosan-essential oil composite films.