Encapsulation of essential oil in emulsion based edible films prepared by soy protein isolate-gum acacia conjugates

Emulsions containing essential oils (EOs) of oregano (OG-EO), lemon (LM-EO), fruit of Amomum tsaoko Crevost et Lemaire (ACL-EO) or grapefruit (GF-EO) were used as dispersed phase and aqueous solution of soy protein isolates-gum acacia (SPI-GA) conjugates was used as continuous phase to produce edible films. The viscosity, oil droplet size distribution, zeta (ζ)-potential, storage and loss moduli and microstructure of film forming emulsions were affected by the type or nature of the EOs used. The microstructure, glass transition temperature (Tg), tensile strength, elongation at break, water vapor permeability, surface hydrophobicity, electrostatic interactions, hydrogen bonds, hydrophobic interactions, disulfide bonds, antioxidative and antibacterial properties as well as the release pattern of EO from the EO containing films were affected by the nature of the EO used. Among these films, the film containing GF-EO showed the best water vapor barrier properties, the highest tensile strength and Tg compared to the films prepared from other EOs. The films containing LM-EO and OG-EO showed the highest radical scavenging activity and antibacterial activity, respectively. The release profiles of EOs from their respective films were fitted well by Peppas model.