Assessing the Role of Gaseous Chlorine Dioxide in Modulating the Postharvest Ripening of Keitt Mangoes through the Induction of Ethylene Biosynthesis.

Consumer acceptance of Keitt mangoes ( Mangifera indica L.) is significantly affected by their slow postharvest ripening. This work used gaseous chlorine dioxide (ClO ₂ (g)) to prepare the ready-to-eat Keitt mango and explored the potential mechanisms for the mango ripening. Harvested mangoes were treated with 20 mg·L ^-1 of ClO ₂ (g) or ethephon for 3 h (25 °C) and left in a climatic chamber with a temperature of 25 ± 1 °C and a relative humidity of 85 ± 5% for 4 d. The results showed that ClO ₂ (g) treatment significantly promoted the orange coloration of mango flesh compared to the untreated control group. Moreover, ClO ₂ (g) treatment significantly elevated the total soluble solids, total soluble sugar, and total carotenoids content of mangoes, whereas the firmness and titratable acidity were reduced. ClO ₂ (g)-treated mangoes reached the edible window on day 2, as did mangoes treated with ethephon at the same concentration, except that the sweetness was prominent. The residual ClO ₂ level of the mangoes was <0.3 mg/kg during the whole storage time, which is a safe level for fruit. In addition, ClO ₂ (g) significantly advanced the onset of ethylene peaks by 0.5 days and increased its production between days 0.5 and 2 compared to the control group. Consistently, the genes involved in ethylene biosynthesis including miACS6 , miACO1 , and miACO were upregulated. In sum, ClO ₂ (g) can be a potential technique to reduce the time for harvested mango to reach the edible window, and it functions in modulating postharvest ripening by inducing ethylene biosynthesis.