Extending the postharvest shelf life of sweet orange (Citrus sinensis L.) fruits using muskmelon seeds flour based edible coatings functionalized with oregano essential oil

The present study investigates the effect of ultrasonicated defatted muskmelon (Cucumis melo L.) seeds' flour-based edible coatings functionalized with oregano essential oil (OEO) on the postharvest shelf-life extension of sweet oranges (Citrus sinensis L.) at room temperature (23 ± 3 °C, RH: 40–45%) up to 15 days. The edible coatings (M2, M3, and M4) with increasing concentrations of oregano essential oil (1%, 1.5%, and 2%, respectively) were significantly (p < 0.05) effective in maintaining the quality attributes of oranges, such as physiological loss in weight (PLW), pH, titratable acidity (TA), total soluble solids (TSS), color, firmness, total phenolic contents (TPC), total flavonoids content (TFC), antioxidant activity (DPPH and ABTS assay), sensory attributes (aroma, texture, color, overall acceptability), and lower microbial load throughout the storage period in comparison to the control samples. The application of M4 treatment (defatted muskmelon seeds’ flour-based edible coating with 2% oregano essential oil and ultrasonication treatment at 40% amplitude for 80 min) maintained higher consumer acceptability in sweet oranges on 15 days of storage with retained higher postharvest quality attributes such as physiological loss in weight (16.80%), pH (4.76), titratable acidity (0.63%), total soluble solids (11.89°Brix), color (L* = 49.84, a* = -3.07, b* = 41.59), firmness (939.86 N), total phenolics content (54.12 mg GAE/g), total flavonoids content (32.62 mg QE/g), antioxidant activity (DPPH = 64.16% and ABTS = 0.72 mmol 100 g⁻¹), and sensory attributes (aroma = 4.77, texture = 4.36, color = 4.56, overall acceptability = 4.56). The control samples had unacceptable microbial and quality attributes on the 9th day of storage. The gas chromatography-mass spectrometry (GC–MS) analysis identified carvacrol, diethyl phthalate, p-Cymene, cyclopropane, trimethyl (2-methyl-1-propenylidene)-, linalool, terbutol, and thymol as significant compounds in the OEO. The results indicated that ultrasonicated defatted muskmelon seeds' flour-based edible coatings enriched with oregano essential oil are eco-friendly and sustainable alternatives to synthetic polymers for maintaining the quality attributes of orange fruits for up to 15 days.