Development of konjac glucomannan based Syringa essential oil film and its fragmented form for quality maintenance of citrus fruits

Citrus fruits have suffered serious losses in postharvest storage and transportation. A novel approach, fragmented konjac glucomannan-based Syringa essential oil (KSE) films, was used to maintain the quality of citrus fruits in storage. The KSE film was successfully prepared by using the encapsulating method via coacervation, with an encapsulation efficiency of 18.3% and loading capacity of 11.4%. GC–MS showed that eugenol, caryophyllene, and humulene were the main constituents of Syringa EO. SEM showed that EO drops or volatiles distributed in the KGM molecular matrix produced a concave structure during film formation. FTIR indicated no interaction or modification between KGM and Syringa EO, and EO was successfully encapsulated into the KGM films. The fragmented KSE films showed significant antifungal activity against Penicillium italicum, Penicillium digitatum, and Geotrichum citri-aurantii, inhibiting spore germination and mycelium elongation, resulting in suspected indentation, plasmolysis, and vacuolization. In storage, the fragmented KSE film packed in a non-woven bag apparently maintained the quality of citrus fruits, including sustaining fruit firmness and reducing vitamin C (VC), total soluble solids (TSS), and titratable acid (TA) loss. One of the modes of action for the quality maintenance of citrus fruits might be induced systemic resistance. This study might convey stronger impact in postharvest by newly developed packaging materials.