Short-term effects of air and controlled atmosphere storage on antioxidant metabolism in conference pears

Conference pears (Pyrus communis) were subjected to regular air storage or controlled atmosphere (CA: 2% O-2 and 5% CO2) storage for 2, 4, 8, or 21 days to compare the short-term effects of these atmospheres on antioxidant metabolism. Total ascorbate content decreased rapidly during storage, especially when the fruits were stored in CA. Under this atmosphere, a significant increase in the oxidised form of ascorbate during the first days of storage was found. Total levels of glutathione also decreased after storage for the two different storage atmospheres, but higher levels in the reduced form of glutathione were found in the CA-stored fruits during the same period. Fruits exposed to CA showed a sharp burst in ascorbate peroxidase (APX) and glutathione reductase (GR) activity immediately after storage. A significant increase in superoxide dismutase (SOD) activity and a late decrease in catalase (CAT) were also found in the CA-stored fruits. Changes in antioxidant metabolism were associated with the accumulation of lipid peroxidation products, a significant increase in lipoxygenase (LOX) activity, and higher amounts in hydrogen peroxide (H2O2), especially when the fruits were exposed to CA. Collectively, these results challenge the hypothesis that CA may be perceived as a stress which involves significant changes in antioxidant metabolism.