Role of fermentative and antioxidant metabolisms in the induction of core browning in controlled‐atmosphere stored pears

Pears (Pyrus communis L cv Blanquilla) were stored at various CO2 concentrations to induce core browning. The severity of core browning and the products and enzymes associated with fermentative and antioxidant metabolisms were determined immediately after harvest and in healthy and damaged fruits after storage. The incidence and severity of brown core increased with CO2 concentration. Acetaldehyde and ethanol concentrations and alcohol dehydrogenase (ADH, EC 1.1.1.1) activity increased in all fruits during storage, but more in fruits with brown core than in healthy fruits. Pyruvate decarboxylase (PDC, EC 4.1.1.1) activity decreased slightly during this time. Ascorbate contents decreased whereas glutathione concentrations increased during storage in fruits with brown core compared to the same fruits at harvest. Superoxide dismutase (SOD, EC 1.15.11) activity increased during storage but was not affected by brown core. In contrast, a significant increase in both ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) activities and a significant decrease in catalase (CAT, EC 1.11.1.6) activity were found in damaged fruits. Malonaldehyde (MDA) and 4-hydroxyalkenal (4-HNE) contents increased significantly in the damaged fruits as a result of peroxidation. Collectively, our results suggest that brown core in pears is indirectly correlated with fermentation and involves oxidative damage which may be a causal factor in brown core development. © 2001 Society of Chemical Industry