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 concentra tions to induce core browning. The severity of core browning and the produc ts and enzymes associated with fermentative and antioxidant metabolisms wer e determined immediately after harvest and in healthy and damaged fruits af ter storage. The incidence and severity of brown core increased with CO2 co ncentration. Acetaldehyde and ethanol concentrations and alcohol dehydrogen ase (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 decarboxyla se (PDC, EC 4.1.1.1) activity decreased slightly during this time. Ascorbat e contents decreased whereas glutathione concentrations increased during st orage in fruits with brown core compared to the same fruits at harvest. Sup eroxide dismutase (SOD, EC 1.15.11) activity increased during storage but w as 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-hydroxy alkenal (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. (C) 2001 Soc iety of Chemical Industry.