Relationship of IAD index to internal quality attributes of apples treated with 1-methylcyclopropene and stored in air or controlled atmospheres

The research was conducted to evaluate the relationship between I-AD index (index of absorption difference between 670 and 720 nm) values and internal quality attributes of apples treated with 1-methylcyclopropene (1-MCP) and stored in air and controlled atmospheres (CA). Apples of '8S6923' (Aurora Golden Gala (TM)), 'Fuji' and 'Royal Gala' were tested. The results with Aurora Golden Gala (TM) show that I-AD index values were maintained at higher levels if the fruit were stored in CA and that 1-MCP had no significant effect on retaining at-harvest values. The I-AD values correlated with chlorophyll a content in the peel (R-2 = 0.95, P<0.0001), but not with chlorophyll b content, internal ethylene levels, firmness or titratable acidity. Royal Gala' apples showed a similar response to Aurora Golden Gala (TM) apples, showing no correlation between I-AD index values and internal quality attributes of those apples when treated with 1-MCP and/or CA. In contrast, 'Fuji' apples showed a relationship between I-AD index value changes and internal ethylene concentrations (R-2 = 0.67, P<0.05) and titratable acidity changes (R-2 = 0.89,P < 0.01), but not firmness. These results suggest that when 1-MCP and/or CA are applied to apples after harvest, that I-AD index values do not consistently correlate to any internal quality attributes other than peel chlorophyll a content. Crown Copyright (C) 2014 Published by Elsevier By. All rights reserved.