Properties of film-forming dispersions and films based on chitosan containing basil or thyme essential oil

• Essential oil loss in chitosan film depended on stability of film-forming emulsion.
• Addition of oleic acid enhanced emulsion stability and reduced essential oil loss.
• Oleic acid decreased water vapour permeability and reduced film transparency.
• Chitosan-essential oil films did not affect fungal growth in an in vitro test.

Film-forming emulsions and films of chitosan containing basil or thyme essential oil, with and without oleic acid were characterised as to the emulsion stability (particle size, ζ-potential and rheological behaviour) and barrier, mechanical and optical properties of the films. The losses of the essential oil during the film formation were also quantified as well as the antifungal effect of the films against Aspergillus niger, Botrytis cinerea and Rhizopus stolonifer.The retention of essential oil in the films was greatly dependent on the stability of the film-forming emulsion. The addition of oleic acid (OA) to the chitosan-essential oil formulations enhanced the emulsion stability and oil retention in the film, at the same time that it improved the water vapour barrier properties of the film. Lipids reduced the film stretchability but when OA was present in the formulation, this reduction was mitigated, as well as the changes in colour provoked by the essential oils, whereas OA reduced the film transparency. Chitosan films with thyme or basil essential oil did not inhibit the growth of the tested fungi.

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