Isolation and Identification of Spoilage Fungi from Green Lemons and Their Inhibition by UV-LED-Induced Composite Coating Solution

This study sought to address the problem that green lemons are highly perishable after harvest in Tongnan, Chongqing. Three spoilage fungal strains (F1, F2, and F3) isolated from naturally decayed green lemons were identified by morphological observation and molecular identification as Penicillium digitatum, P. jacksonii, and P. italicum, respectively. Subsequently, the inhibitory effects of ultraviolet (UV)-light emitting diode (LED)-induced chitosan (CTS)-TiO₂-Ag composite coating solution against these fungi was evaluated. The results revealed that all UV-LED-induced CTS-TiO₂-Ag treatments inhibited each of these strains, and the effect was more pronounced than that of UV-only treatment. Moreover, for each treatment, the diameter of the inhibition zone increased with prolonged light induction, the mycelial dry mass decreased, the inhibition rate of mycelial growth rose, and extracellular electrical conductivity as well as protein and nucleic acid leakage increased. Overall, under the same light induction time, UV-LED red light treatment showed the best fungal inhibitory effect. This study provides theoretical support for developing lemon preservation technology.