Melaleuca alternifolia essential oil loaded chitosan nanocomposite coating against Alternaria alternata spots and rotting of tomato fruits

In the present study, Melaleuca alternifolia essential oil loaded chitosan nanocomposite (CS-N-MAEO) was developed and its antifungal coating efficacy on tomato (Solanum lycopersicum L.) fruits was investigated. The CS-N-MAEO was characterized through scanning electron microscopy, dynamic light scattering, fourier transform infrared spectrometry, and x-ray diffractometry analyses with controlled delivery property. The CS-N-MAEO displayed superior inhibitory activity against Alternaria alternata growth at 2.0 µL/mL as compared to unencapsulated MAEO. The CS-N-MAEO caused detriment in ergosterol synthesis and outflow of ions, nucleic acids, and proteins validating plasma membrane as the main target site of action. Moreover, in silico homology modeling displayed strong interaction of terpinen-4-ol with Cytochrome P₄₅₀ 14α-demethylase protein causing inhibition of ergosterol biosynthesis. The CS-N-MAEO nanocomposite coating helped the tomatoes to maintain the lowest weight loss (5.87%) and total soluble solids (9.09%) while the highest titrable acidity (0.567%) and phenolic content (9.89 µg/mL gallic acid) as compared to control during 15 days of storage at 20 ± 2 °C (RH ~ 65%). Furthermore, the CS-N-MAEO coating strictly impeded the respiration rate (11.19 mg CO₂/kg/h) and significant (p < 0.05) induction of ascorbate peroxidase, superoxide dismutase, and catalase activities along with maintenance of sensory qualities of fruits. The result of this study provides an innovative idea for the development of antifungal nanocomposite coating against A. alternata mediated fruit deterioration.