Correlating emulsion characteristics with the properties of active starch films loaded with lemongrass essential oil

Abstract

Edible films supplemented with active ingredients are promising for food packaging and preservation. Numerous plant essential oils present antimicrobial activity against pathogenic microorganisms, but their low solubility in water limits food-related applications. Emulsification is herein exploited as a means of improving the dispersion of such active substances in water, imparting increased functionality and reduced degradation. Lemongrass essential oil (LEO) was directly emulsified as dispersed phase into aqueous solutions of pectin, which was used together with Tween 80 as polymeric emulsifiers. LEO nano- and micro-sized droplets were added to film-forming formulations based on glycerol-plasticized cassava starch (TPS) and then dried into films by continuous casting. LEO contents in films relied upon microbiological assays to ensure antimicrobial activity. Films’ chemical composition, morphological, thermal, mechanical, and barrier properties, in addition to biodegradability in vegetal compost, were comprehensively studied. In general, emulsions were suitably dispersed within the TPS matrix, both phases showing good interaction and compatibility. Emulsification caused important changes in the TPS-based films, such as improved colorimetric attributes, thermal stability, barrier to moisture, and mechanical properties. Another key observation was the maintenance of the biodegradation profile in soil of TPS after the addition of LEO emulsions. Overall, the emulsification approach was successful in providing TPS films with multifunctionality by the supplementation of an active substance without negatively affecting its fundamental properties for food packaging applications.