Gaseous chlorine dioxide improves Keitt mango quality during postharvest ripening: enhancing sugar accumulation, terpenoid biosynthesis, and storage performance

Keitt mango (<i>Mangifera indica</i> L.) is typically harvested at full size and mature green, then allowed to ripen naturally at room temperature for several days. However, this process yields fruit that lacks the ideal sweetness and characteristic mango flavor compared to tree-ripened mangoes. To enhance the postharvest ripening quality of Keitt mangoes, the mangoes were subjected to gaseous chlorine dioxide (ClO₂, cumulative concentration 200 μL/L), then stored at 25 °C with 85 ± 5% humidity for 4 days. Results suggested that gaseous ClO₂ treatment significantly elevated the levels of melibiose, glucose, mannose, and arabinose in mango pulp during days 1-4 compared to the control and ethephon-treated groups, with the most pronounced increase observed in glucose content. For aroma, gaseous ClO₂ treatment remarkably elevated the content of terpenoids, especially 3-carene, on days 2-4. These trends were consistent with the upregulated expression of genes encoding sugar production (<i>MiSUS</i>, <i>MiBAM3</i>, <i>MiabfA</i>, and <i>MiHEX1</i>), terpenes biosynthesis (<i>MiACAT</i>, <i>MiIDI</i>, and <i>MiGPPS</i>), and vacuolar sugar transporters (<i>MiERD6-5</i> and <i>MiERD6-6</i>). Additionally, gaseous ClO₂-ripened mangoes achieved outstanding quality attributes compared to ethephon-ripened mangoes after 4 days of storage at 13 °C. In summary, gaseous ClO₂ can effectively promote sugar accumulation and flavor development in Keitt mangoes, as well as yield superior storage quality. These findings indicate a remarkable potential for gaseous ClO₂ in enhancing the quality of postharvest fruits.