This research developed a biofilm integrating poly lactic acid (PLA) with a composite hydrophobic nanoemulsion (C-HyDEN) to evaluate their effectiveness in water barrier properties, gas permeability, and impact on the firmness of postharvest mango. We analysed Chitosan-HyDEN and Konjac-HyDEN films for water uptake (WU), water vapor permeability (WVP), diffusion coefficient, and gas permeability. We compared the best performance of composite coating to a single hydrophobic nanoemulsion (HyDEN) film in terms of mango firmness. Chitosan-HyDEN film demonstrated a significantly lower WU (1.06%) than Konjac-HyDEN film (2.14%). The Chitosan-HyDEN film exhibited lower WVP than the Konjac-HyDEN film, indicating its superior nanofiltration capabilities. Chitosan-HyDEN film had a higher diffusion coefficient than KonjacHyDEN film, underscoring its effectiveness in reducing fruit water loss during storage. Composite film also proved more effective in controlling gas permeability than single HyDEN film. Due to its outstanding water barrier properties, ChitosanHyDEN film was selected for firmness testing on postharvest mangoes, where it achieved the highest firmness retention (806.08±3.59 N) compared to single HyDEN film (614.26±3.55 N) and the commercial fungicide Antracol (174.75±5.35 N). These results indicate that Chitosan-HyDEN significantly enhanced the film's properties and effectiveness, thereby improving fruit products’ storage life, safety, and quality. Keywords: composite hydrophobic nanocoating, chitosan, konjac, antracol