Reduced ethylene synthesis of mangoes under high CO₂ atmosphere storage

ABSTRACT.

High CO₂ atmospheres have been reported to be accountable for slower ripening processes of many fruit species. In modified or controlled atmosphere storage of mangoes (Mangifera indica L.) delayed ripening is attributed to the effects of CO₂ on ethylene biosynthesis, which is reduced under CO₂ concentrations beyond 10%. In the present work the objective was to determine if those elevated CO₂ atmospheres on ethylene synthesis could be attributed to the action of CO₂ upon ACC oxidase. Mature green or tree ripe `Tommy Atkins` mangoes were, in four experiments, held in a flow through system of either 10 or 25% CO₂ mixed to 5% O₂ or only air for 14 or 21 days at 5, 8 or 12°C. Mangoes in the 25% CO₂ atmosphere did not produce detectable levels of ethylene, whereas under 10% CO₂ the production rates were significantly suppressed at 5 or 8°C. However, 1-aminocyclopropane-1-carboxylic acid (ACC) concentrations in mango mesocarp tissue at retrieval from storage were similar to the air controls and ACC synthase activity was not completely inhibited. The direct effects of CO₂ concentrations on ACC oxidase activity is to be considered the most important factor in inhibiting ethylene biosynthesis of mangoes under 25% CO₂ atmospheres.

Keywords:
1-aminocyclopropane-1-carboxylic acid; ACC oxidase; ACC synthase; Mangifera indica