Effect of 1-MCP on quality and antioxidant capacity of in vitro digests from 'Sunrise' apples stored at different temperatures

The antioxidant capacities of phenolic and non-phenolic fractions for in vitro digestates from 'Sunrise' apple were assessed after postharvest application of 1-methylcyclopropene (1-MCP), a ripening inhibitor, and three weeks storage at 5, 13, 15, 18 and 22 degrees C. An in vitro digestion system was used to generate the soluble bioaccessable digestate which was then fractionated into phenolic and non-phenolic fractions. The two fractions were assayed for Folin-Ciocalteu Reaction (FCR) reducing capacity and peroxyl radical scavenging capacity. Quality retention of the fruit was assessed by measuring internal ethylene concentration, firmness and titratable acidity. Treatment with 1-MCP inhibited internal ethylene concentration and better maintained the firmness and titratable acidity of 'Sunrise' summer apples as compared with untreated control apples at storage temperatures of 15 degrees C and above. The FCR reducing capacity of the phenolic fraction of the in vitro, simulated gastrointestinal digestates showed similar response as did the quality measures, with significantly higher activity in the 1-MCP treated fruit at higher storage temperatures. However, no consistent differences were found between 1-MCP and control treatments for the FCR reducing capacity of the non-phenolic fraction or for the peroxyl radical scavenging capacity of either fraction. The non-phenolic fractions consistently had higher levels of both types of antioxidant capacities. Treatment and storage of 'Sunrise' apples at elevated temperatures (>13 degrees C) resulted in improved fruit quality and retention of reducing capacity in simulated gastrointestinal digestates. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.