Cold storage duration influences ethylene biosynthesis and ripening of 'Bartlett' pears

Ripening behavior of 'Bartlett' pears (Pyrus communis L.), with or without ethylene (C2H4) treatment, was assessed at harvest, and after 2, 4, 6 and 12 weeks of cold storage at -1 degrees C. Fruit exhibited increasing rates of C2H4 production and consequently faster ripening rates n with increased length of cold storage. Ripening characteristics were influenced by storage duration, but to different degrees. The data indicate that the threshold C2H4 concentration for softening may be lower than that for color change from green to yellow. Ethylene treatment for 24 h at harvest resulted in a rate of ripening equivalent to that following cold storage for 2 to 4 weeks, depending on the orchard location. Storage for 12 weeks significantly increased C2H4 production upon transfer to ambient temperature, indicating that fruit were reaching the end of their storage life. 'Bartlett' pears may ripen to a firmness of 14 N (ready to eat) at 20 degrees C within 2.5 to 7 days depending upon the duration of prior cold storage.