Evaluation of the Effect of Sodium Alginate Combined with Thyme Essential Oil on the Postharvest Shelf Life of Washington Navel Orange (Citrus sinensis cv. Washington Navel)

Citrus fruits, belonging to the Rutaceae family, are among the most widely cultivated fruits worldwide. Oranges are one of the most consumed fruits globally; however, they are prone to postharvest issues such as weight loss, decay, and physiological disorders. In an effort to enhance the storability of oranges, extensive research has been conducted on the application of edible coatings in the postharvest phase. Sodium alginate and its derivatives exhibit numerous biological activities, including antioxidant, coagulating, antimicrobial, biocompatibility, wound healing, low toxicity, and tissue engineering effects. This study investigated the effect of sodium alginate coating enriched with thyme essential oil on the quality and postharvest shelf life of Washington Navel oranges. The results demonstrated that the combined coating of sodium alginate and thyme essential oil delayed the respiratory peak, thereby preventing weight loss. Additionally, it maintained acidity and soluble solid content during storage. Similarly, the combined coatings were effective in preserving fruit firmness. Furthermore, these coatings maintained cellular membrane integrity by reducing relative electrolyte leakage, which delayed fruit senescence during long-term storage. The coatings also enhanced the total phenolic content, flavonoids, and ascorbic acid, thereby increasing the antioxidant capacity. In conclusion, sodium alginate combined with thyme essential oil can serve as a promising, effective, and non-toxic strategy for preserving the nutritional quality and membrane integrity of oranges.