Involvement of oxidative processes in the development of core browning in controlled-atmosphere stored pears

'Blanquilla' pears (Pyrus communis) were harvested 3 d after the estimated ideal time for commercial harvest and stored for six months in controlled a tmosphere (CA) at 2% O-2 + 0.7% CO2, 2% O-2 + 5% CO2 or in air at -0.5 degr eesC. The incidence Tof core browning, concentrations of ascorbate and glut athione and activities of superoxide dismutase (SOD), catalase (CAT), ascor bate peroxidase (APX), glutathione reductase (GR) and Lipoxygenase (LOX) we re measured after storage. Core browning only occurred in pears stored at 5 % CO2. It was associated with the accumulation of lipid peroxidation produc ts (ethane and thiobarbituric acid reactive substances - TEARS), which is e vidence of increasing oxidative damage during CA storage. Lower ascorbate c oncentrations were observed in CA stored fruits. Despite an important incre ase in the amount of glutathione at the end of the storage, no significant differences were found for the different atmospheres. Concomitantly, the ac tivity of SOD, APX and LOX increased during storage and were significantly higher in the fruit stored in 5% CO2. In contrast, only slight differences in the activities in CAT and GR were observed. It is therefore suggested th at fruit susceptibility to CO2-induced core browning is due to oxidative da mage and lipid perodixation, and strongly influenced by ascorbate.