Abstract:The effects of different concentrations of chitosan combined with 0.5 mg/mL trisodium phosphate at ambient temperatures on the development of lesions in apples （cv. Golden Delicious）inoculated with Penicillium expansum was investigated. The effects of an optimal combination of chitosan and trisodium phosphate on the activity of antioxidant enzymes，as well as other enzymes，and on the accumulation of metabolites in the phenylpropanoid pathway were also studied. The results indicated that 1.0% chitosan combined with 0.5 mg/mL trisodium phosphate was the most effective treatment for the inhibition of the growth of blue mold in apples.Importantly，the combination of chitosan and trisodium phosphate significantly reduced the lesion diameter in the inoculated fruits and increased the contents of total phenolic compounds，flavonoids，and lignin，and the activities of peroxidase and phenylalanine ammonia -lyase in apples. Furthermore，this combination increased the H2O2 contents，and the catalase，ascorbate peroxidase，and glutathione reductase activities in apples. Collectively，these findings suggested that the combination of chitosan and trisodium phosphate inhibits the formation of blue mold in apples via the enhancement of antioxidant capacity and the activation of the phenylpropanoid pathway.