Intermittent warming effects on superficial scald development of 'Cortland', 'Delicious' and 'Law Rome' apple fruit

'Cortland', 'Delicious' and 'Law Rome' apples were intermittently warmed to 20 degrees C for 24 h every 1, 2, or 4 weeks during cold storage for 16 weeks, not warmed, or treated with diphenylamine (DPA) at harvest. The effects of these treatments on fruit ripening and on the accumulation of alpha-farnesene and its oxidation products in hexane extracts of the peel, were assessed throughout storage. Incidence and severity of superficial scald were assessed after 22 weeks. Warming treatments, especially the weekly regime, advanced fruit ripening. Without warming, scald incidence in 'Cortland', 'Delicious' and 'Law Rome' was 70, 14 and 85%, respectively. Intermittent warming treatments reduced scald but the magnitude of effects varied among cultivars. In 'Cortland', scald was reduced only by the weekly warming treatment, which was less effective than DPA treatment. In 'Delicious', all warming treatments were equally effective but less so than DPA. In 'Law Rome', weekly warming controlled scald better than DPA, but less frequent warming was proportionately less effective in controlling the disorder. Concentrations of conjugated trienes measured at 281 nm were not related consistently to scald incidence after storage, but ratios of measurements at 258 and 281 nm in crude hexane extracts were. The results are discussed in relation to the a-farnesene hypothesis of scald development and chilling injury. (C) 1999 Elsevier Science B.V. All rights reserved.