Novel multilayer chitosan/emulsion-loaded syringic acid grafted apple pectin film with sustained control release for active food packaging

The clove essential oil (EO) emulsions were prepared using syringic acid grafted apple pectin (SAAP) and soy protein isolate (SPI). This emulsion was used to improve properties of pullulan film (inner layer), which can be used for active packaging. Furthermore, chitosan was employed as the outer layer of the multilayer film prepared to address the limitations of existing pullulan films. Mechanical, optical, and functional properties of multilayer films were determined. The emulsions produced by SAAP display better emulsifying properties, smaller and uniform droplet size distribution. In comparison with AP-SPI-Pul, water vapor and oxygen permeabilities of SAAP-SPI-Pul were lower, while antioxidant, antimicrobial properties and barrier properties to UV were improved. Chitosan film can be used as the outer layer to modify the hydrophilicity/hydrophobicity of films with water contact angle of 98.4°. SAAP-SPI-Pul-Chit film has characteristics of high-performance films with favorable optical and mechanical properties. Furthermore, antioxidant and antimicrobial properties, as well as fruit preservation properties of the SAAP-SPI-Pul-Chit films were strengthened, which is attributed to the sustained release of clove EO in films.