Chitosan/pullulan edible coatings containing thyme essential oil nanoemulsion: Preparation, characterization and...

In order to extend the shelf life of fruits, edible coatings have been widely studied as a potential alternative strategy to traditional preservatives. This study developed a novel chitosan (CH)/pullulan (PUL) composite edible coating incorporated with 2 % thyme essential oil nanoemulsion (TEON) to enhance antifungal and preservative properties, which consisted of five CH/PUL edible coating groups: C100, C100/T, C75/P25/T, C50/P50/T and C25/P75/T. TEON was characterized using dynamic light scattering (DLS) and transmission electron microscopy (TEM), revealing an average particle size of 89.56 nm. In vitro antifungal test demonstrated that the CH coating with TEON reduced Botrytis cinerea mycelial area from 14.03 mm² to 6.35 mm² compared to C100 coatings, achieving a 54.7 % inhibition rate. The microstructure, mechanical properties, antifungal properties, and the effect of CH/PUL edible coating on the preservation of strawberry were investigated. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) confirmed intermolecular interactions between CH and PUL. The addition of PUL increased the water permeability of CH-based films from 0.69 m²‧h‧kpa to 0.13 m²‧h‧kpa and the tensile properties from 45 % to 88 %. Strawberry preservation at 2 °C for 12 days showed C50/P50/T-treated samples had the lowest weight loss, decay incidence, and Botrytis cinerea area, compared with the other treatment groups. In summary, this paper successfully developed CH/PUL edible coating with antifungal and preservation effects, which have potential applications in improving strawberry quality and extending the storage period of strawberries.