Structural, morphological and thermal behaviour characterisations of fish gelatin film incorporated with basil and citronella essential oils as affected by surfactants

• Distribution of essential oil droplets in film was governed by surfactants.
• Types of surfactants directly affected structure, morphology and thermal properties of film.
• Gelatin/essential oil films prepared with soy lecithin were homogeneous and stable.

Structural, morphological and thermal properties of fish skin gelatin films incorporated with basil and citronella essential oils at a ratio of 1:1 (w/w), as influenced by different surfactants (Tween-20, Tween-80 and soy lecithin at 25% based on essential oil), were characterised. Smoother surface and more homogeneous oil distribution was observed via SEM in films containing both basil and citronella essential oils when soy lecithin was used as surfactant. Essential oil containing gelatin films exhibited bi-layer morphology when Tween-80 was used as surfactant. FTIR results suggested the decreased protein–protein interaction in the matrix of gelatin film when essential oils were incorporated, depending on type of surfactants used. Films added with both essential oils had lower glass-transition and degradation temperatures than the control films, indicating a poorer protein–protein interaction in film network. Therefore, both essential oils and surfactants had the impact on molecular structure and thermal properties of resulting films.

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