ETHYLENE FORMATION, LIPOXYGENASE ACTIVITY AND CALCIUM CONTENT IN APPLE (CV. JONAGOLD)

Several times during storage the lipoxygenase (LOX) activity and the levels of 1-aminocyclopropane-1-carboxylic acid (ACC) and N-malonyl-ACC (MACC) of fruit flesh disks were measured on apples (cv. Jonagold) differing by their K/Ca ratio. The LOX activity of the 8 mm of fruit flesh taken just beneath the peel was lower in fruits with a low K/Ca than in fruits with a high K/Ca ratio. In the same fruit zone the level of ACC was lower in the low K/Ca fruits but no significant difference could be shown in the level of MACC. There were significant differences in LOX activity between the dates of measurements. In our conditions and in the analysed fruit zone a peak of activity was found in January, after 3 months of storage. After a shelf life of 8 days at room temperature there was a sharp increase of LOX activity. Fruits with a high K/Ca ratio and a higher LOX activity showed more physiological disorders (bitter pit and internal breakdown) during storage. The observed differences did not seem to be attributed to the different fruit fresh weights of both series of apples (low and high K/Ca). The LOX activity was positively correlated with the MACC level and the K/Ca ratio of fruit flesh disks.