Control of apple superficial scald and ripening - a comparison between 1-methylcyclopropene and diphenylamine postharvest treatments, initial low oxygen stress and ultra low oxygen storage

'Granny Smith' apple (Malus domestica Borkh.) fruit were treated with 1 mul l(-1) 1-methylcyclopropene (1-MCP) at room temperature for 12 h. Quality of fruit stored 4 and 6 months in air, under different controlled atmospheres (CA) at low oxygen concentration (1.5, 1.0 and 0.7 kPa O-2), with initial low oxygen stress (ILOS) at 0.4 kPa O-2 for 2 weeks, and with or without postharvest application of the antioxidant diphenylamine (DPA) were compared. Superficial scald was controlled after long-term storage under 0.7 kPa O-2 or with ILOS followed by 1.0 kPa O-2, but not solely under 1.0 kPa O-2. 1-MCP eliminated the incidence of superficial scald under all long-term air and CA storage conditions. Core flush incidence was not affected by ILOS, but decreased at lower O-2 concentrations, and was reduced by 1-MCP or DPA. A disorder, resembling external CO2 injuries, was observed on about 2.5% of fruits of all maturity stages treated with 1-MCP and subsequently stored in CA. Fruit treated with 1-MCP maintained greater firmness and acidity, even after 14 days at 20degreesC, than untreated fruit stored under low oxygen. Total soluble solids concentrations were not influenced by 1-MCP. Degreening was effectively inhibited by 0.7 kPa O-2 or ILOS immediately after storage, but only by 1-MCP during the subsequent ripening period. (C) 2002 Elsevier Science B.V. All rights reserved.