Study on physicochemical properties, antioxidant and antimicrobial activity of okara soluble dietary fiber/sodium carboxymethyl cellulose/thyme essential oil active edible composite films incorporated with pectin

Active edible films based on okara soluble dietary fiber (SDF), pectin, sodium carboxymethyl cellulose (CMC–Na) and thyme essential oil (TEO) were successfully prepared. We aimed to exploit biodegradable edible films and realize the full utilization of waste resources. The effects of different amounts of pectin on the properties and structural characterization of the composite film with or without TEO were studied using a solution casting evaporation method. In general, the addition of TEO can improve the properties of the composite membrane. Pectin was homogeneously distributed within the films and exhibited good interaction with the polymer matrix. The addition of pectin led to significantly higher mechanical and optical properties of the composite film, compared with SDF/CMC-Na composite film. The tensile strength reached 21.419 ± 2.22 MPa, and the minimum transparency reduced to 88.9% ± 0.42%, with increasing pectin. Notably, the water resistance and oil resistance were enhanced. The composite films also possessed satisfactory antioxidant activity, with a DPPH-free radical scavenging rate of 46.33% ± 0.72%, while antibacterial activity against E. coli and S. aureus bacteria was not obvious. Antioxidant and antibacterial SDF/pectin/CMC-Na composite films with enhanced mechanical, optical and barrier properties are excellent candidates for active edible packaging.