Development and characterization of bael (Aegle marmelos) leaf extract incorporated chitosan-based functional edible coating and its application on stored tomatoes

Abstract

A bael (Aegle marmelos) leaf extract (BLE) incorporated chitosan-based functional edible coating was developed in this study. The incorporated functional extract exhibited high 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging antioxidant activity amounting up to 74.35 ± 0.21%, and impressive antimicrobial properties as high as 5 mg mL⁻¹. As a functional extract, BLE contributed excellently by controlling the ripening of the coated tomatoes stored at ambient temperature. This was evidenced by the recorded patterns of the respiration rate (RR), ΔE color, weight loss, total soluble solids (TSS), titratable acidity (TA), pH, and firmness. The inhibition of mesophilic bacterial and fungal growth contributed remarkably to the enhanced shelf-life of the coated tomatoes. A moderate 1% BLE in the coating (coded BLCT-1) resulted in up to a 250% increase in shelf-life. Scanning Electron Microscopy (SEM) revealed appropriate gelling, coating homogeneity, interblending and continuous surface morphology. Such an excellent texture could be related to the lowered crystallinity of BLCT-1. The characteristic X-ray diffraction peaks suggested the occurrence of chitosan crystal forms I and II in the control as well as BLE incorporated films. Infrared spectra confirmed specific chemical interactions between BLE compounds and chitosan, including the stretching of OH, NH and CO (3360 cm⁻¹ and 967–1195 cm⁻¹ respectively), bending of NH₂ (1600 cm⁻¹), and the evidence of residual acetic acid at around 1700 cm⁻¹. With suitable thickness (0.08 ± 0.001 mm), water vapor permeability (WVP, 0.065 ± 0.002 × 10⁻¹¹ g cm⁻¹ s⁻¹ Pa⁻¹), percentage solubility (PS, 11.889 ± 0.04%) and optical parameters (ΔE: 1.06 ± 0.01), BLCT-1 could be considered as the most ideal edible coating for tomatoes with possible applicability in other perishable fruits and vegetables.