Effect of Nano-TiO2-Reinforced Sodium Alginate Coating on the Postharvest Quality of Edor Longan During Refrigerated Storage

Longan is highly susceptible to moisture loss and quality deterioration during postharvest storage. In the present study, a sodium alginate (SA)/TiO2 nanocomposite edible coating was developed and evaluated for its effects on the physicochemical and antioxidant properties of Edor longan during refrigerated storage. TiO2 nanoparticles with particle sizes of approximately 10.8 ± 2.6 nm were incorporated into the SA matrix using ultrasonic homogenization to prepare composite films. The physicochemical, mechanical, barrier, and optical properties of the films were characterized, and the effects of the coatings on longan quality were evaluated during storage at 4 °C for 63 days. Incorporation of TiO2 significantly increased the tensile strength and Young’s modulus of the SA film, while improving its water vapor barrier performance. Compared with uncoated fruit, the SA/TiO2 coating significantly reduced weight loss and slowed the decline in total soluble solids, ascorbic acid, total phenolic content, and DPPH radical-scavenging activity during storage. At day 63, SA/TiO2-coated fruit exhibited lower weight loss and retained higher levels of ascorbic acid, total phenolic content, and antioxidant activity than both SA-coated and uncoated fruit. SEM observations further showed less pronounced deterioration of the pericarp microstructure in SA/TiO2-coated fruit after storage. These results demonstrate that the SA/TiO2 coating was effective in delaying selected physicochemical and antioxidant changes in Edor longan during refrigerated storage.