Physicochemical and Functional Characterization of Cucumis sativus L. (Poona Kheera) Mucilage and Its Application as a Coating to Inhibit Enzymatic Browning in Fresh-Cut Apples

Enzymatic browning is a major challenge in maintaining the quality and shelf life of fresh-cut fruits, and in this context, plant-derived hydrocolloids are increasingly recognized as sustainable alternatives to synthetic additives due to their ability to retard browning while supporting quality retention. Therefore, in the present study, <i>Cucumis sativus</i> L. mucilage was extracted using microwave irradiation, yielding 24.56% freeze-dried irregular particles with an average size of 194.5 nm and -19.8 mV zeta potential. Various characterization techniques confirmed the amorphous structure and the presence of polysaccharides functional group. The mucilage was primarily composed of glucose (32.27%), along with arabinose, galactose, xylose, mannose, rhamnose, and minor uronic acids, reflecting a glucose-rich heteropolysaccharide. Functionally, the mucilage exhibited notable water retention (8.46 g/g), oil retention (3.21 g/g), foaming capacity (52.13%) with stability (30.46%), emulsifying capacity (90.45%) with stability (91.62%), and solubility (90.14%). Antioxidant assays revealed strong ferric reducing power (5.1 mM FeSO₄ at 10 mg/mL), DPPH scavenging (67.50%; IC₅₀ = 1.798 mg/mL), and ABTS scavenging (60.14%, IC₅₀ = 8.038 mg/mL). Anti-inflammatory evaluation indicated enhanced macrophage viability (1.38-fold at 25 mg/mL) with reduced nitric oxide production, while tyrosinase inhibition reached 60.40% (monophenolase) and 68.50% (diphenolase) at 2 mg/mL. Furthermore, when applied as an edible coating on fresh-cut apple slices, <i>Cucumis sativus</i> L. mucilage effectively delayed enzymatic browning in a dose-dependent manner, with 2 mg/mL maintaining apple slice brightness (L* value; 71.08) and minimizing color change (ΔE = 4.54). Overall, these findings highlight <i>Cucumis sativus</i> L. mucilage as a multifunctional biopolymer with promising applications in food systems and edible coatings.