Fruit ripening of Solo Sunrise, Tainung #2 and Red Lady papaya at two temperatures

Abstract: The process of ripening was evaluated in three papaya cultivars, Solo Sunrise (SS), Tainung #2 (T2) and Red Lady (RL) with different mean fruit weights of 387, 1364 and 2266 g and fruit cavity void volumes of 56, 334 and 502 mL and fruit weight/cavity void volume ratios of 6.9, 3.8 and 4.3 g mL^-1, respectively. The evaluation was done by comparing physiological determinants of the ripening process; ethylene (C₂H₄) generation and respiratory CO₂ production, measured at two temperature ranges, 20-22^oC and 28-30^oC, by sampling cavity void volumes, with physico-chemical quality characteristics of ripening: skin colour, flesh firmness and pH. Fruit ripening of the three cultivars was delayed at the lower temperature range as measured both by physiological determinants including pre-and peak climacteric rates and physico-chemical quality characteristics. However, cv RL showed slower ripening than cvs SS and T2 at both temperature ranges, probably partly related to its low fruit weight/cavity void volume of 4.3 g mL^-1. Moreover, there were negative temporal displacements for skin degreening compared with those for flesh softening, respiration and ethylene generation in fruit of the three cultivars. Fruits of cvs SS and T2 were fully ripened in 8 days after harvest (DAH) and RL fruits in 10 DAH at the lower temperature range. Values for C₂H₄ generation and CO₂ production measured in the fruit cavity are judged to be sensitive indicators of the progress in the process of ripening.