Internal browning disorder of eight pear cultivars affected by bioactive constituents and enzyme activity.

Internal browning (IB) is a disorder in pears that is frequently observed in some cultivars. The present research was carried out to study biochemical changes and IB disorder of pear fruit during storage and ripening. Eight pear cultivars harvested and stored at 1°C up to 90 days. IB incidence, some bioactive compounds, polyphenol oxidase (PPO), peroxidase (POX), and superoxide dismutase (SOD) enzymes activities were measured during storage. IB increased during storage time but the susceptibility of cultivars was different. The ascorbic acid (AA), antioxidant capacity (AC) and SOD activity decreased while POX activity increased during storage but the rate of changes were different in studied cultivars. Total phenol (TP) and total flavonoid (TF) average content varied among pear cultivars and the highest TP and TF were observed in 'Bakhi' cultivars during storage. Fruit IB had positive correlation with the PPO activity, but negative correlation with TP, AC and AA.