Preparation of crosslinked active bilayer film based on chitosan and alginate for regulating ascorbate-glutathione cycle of postharvest cherry tomato (Lycopersicon esculentum)

In the present study, a bilayer film composed of chitosan and alginate was produced by layer-by-layer casting and crosslinking by oxidized ferulic acid. The effects of different film components on mechanical, permeable and optical properties of the film were systematically investigated and the optimum concentrations were determined. The results of scanning electron microscopy and thermogravimetric analysis showed that the crosslinked bilayer film had a smoother and more uniform appearance than the uncrosslinked bilayer film, while the thermal stability was not significantly different. In addition, the infrared measurements confirmed the existence of crosslinking. Subsequently, citric acid was added as an active compound to the bilayer film, which endows the film with antioxidant capacity. Its optimum concentration was also determined by measuring the mechanical, permeable and optical properties of the film. Finally, the active bilayer film was applied to preserve the postharvest cherry tomatoes. The result found that it could well regulate the ascorbate-glutathione cycle in cherry tomatoes and alleviate the accumulation of oxidative damage during postharvest.