Controlled Atmosphere pO2 Alters Ripening Dynamics of 1-MCP treated ‘d’Anjou’ Pear (Pyrus communis L.) Fruit

Abstract

Ripening and development of physiological disorders and decay were assessed in ‘d’Anjou’ pear fruit after 1-methylcyclopropene (1-MCP) treatment and cold storage in air or controlled atmosphere (CA). Fruit were exposed after harvest to 0 or 12.6 μmol·L−1 1-MCP and then stored at 0.5 °C in air or 1, 3, or 5 kPa O2 with 0.5 kPa CO2. Pears were held poststorage at 20 °C for 7 days before analysis. 1-MCP fruit usually had higher hue compared with controls. Softening after removal from storage was delayed in 1-MCP fruit regardless of storage atmosphere; however, control fruit stored in air or CA ripened to below 23 N, a minimum value for consumer acceptance, after all storage durations. 1-MCP fruit stored in air, 3, or 5 kPa O2 softened in the outer cortex (fruit surface to 8 mm into the cortex) to below 23 N only after 9 m, however, only fruit stored in air softened to less than 23 N in the inner cortex (8 mm to coreline). 1-MCP treatment also delayed deformation in cortex tissue tensile strength (TTS); after six or more months, 1-MCP fruit TTS was lower compared with those for control fruit. After 9 m, 1-MCP fruit stored in air had TTS values similar to those of controls whereas values for fruit stored in CA increased with CA O2 concentration. Titratable acidity was higher in 1-MCP-treated fruit stored in air (6 m only) or 3 or 5 kPa O2 compared with controls. Superficial scald developed after 6 m on control fruit stored in air or 5 kPa O2 and on control CA fruit regardless of O2 concentration after 9 m. No 1-MCP fruit developed scald. The results indicate ‘d’Anjou’ pear ripening in response to 1-MCP is influenced by storage pO2 as well as storage duration, and at the 1-MCP treatment concentration used, softening to a consumer standard for firmness occurred only in fruit cold stored in air for 9 months plus a 7-day poststorage ripening period. These fruit had peel hue less than 100, and the yellow peel color may not be consistent with current market expectations.