Enzymatic activities related to cherimoya fruit softening and sugar metabolism during short-term controlled-atmosphere treatments

The effects of short controlled-atmosphere (CA) treatments, involving exposure to 10% O2 combined with 10%, 15% and 20% CO2, on a selection of biochemical parameters and related enzymatic activities of cherimoya fruit were studied. A marked increase in the activity of soluble and cell-wall invertases was found in cherimoyas stored in air, but this was inhibited by CA treatment, which also reduced the accumulation of soluble sugar and malic acid. CA had no effect on the citric acid content and enhanced the rise in fumaric acid concentration, which was directly related to the CO2 level. Differences in the softening of fruit stored in air and in CA were found after 9 days of storage, but the role of the cell-wall hydrolases polygalacturonase and carboxymethyl-cellulase in this behaviour was not elucidated.