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, Cucumis sativus 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, Cucumis sativus 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 Cucumis sativus L. mucilage as a multifunctional biopolymer with promising applications in food systems and edible coatings.