Internal disorders of 'Rocha' pear affected by oxygen partial pressure and inhibition of ethylene action

Current technologies allowing the use of extremely low oxygen partial pressures (pO2), the introduction of 1-methylcyclopronene (1-MCP), and the regulatory prohibition of diphenylamine are changing the conventional storage protocols for pear cultivars. Internal disorders, in particular, severely damage pear quality during controlled atmosphere storage. 'Rocha' pear (Pyrus cummunis L.) was stored for 136 d at −0.5 °C in air or under 3.0 and 0.5 kPa O2 with 0.6 kPa CO2. Fruits treated with 150 nL L−1 1-MCP were also stored at 3.0 and 0.5 kPa O2 after 32 d in air following the treatment. Internal disorders did not develop in fruit stored in air (20.8 kPa O2) or at 0.5 kPa O2 but affected 10.2% of the fruit stored in 3.0 kPa O2 after 136 d. 1-MCP increased disorder incidence at 0.5 and at 3.0 kPa O2. Four types of internal disorders occurred: core browning, white cavity, necrotic cavity, and flesh browning. Low O2 reduced ethylene production and respiration rates which were further reduced by the treatment with 1-MCP. ATP concentration and adenylate energy charge were higher in fruit stored in air than in those at 3.0 and were generally lowest in fruit at 0.5 kPa O2. The effect of pO2 on energy metabolism prevailed over that of 1-MCP treatment. The linkage between ATP and adenylate energy charge (AEC) and the incidence of internal disorders was not strong, since under the same pO2, 1-MCP enhanced the incidence of disorders with a negligible effect on adenylate nucleotides or AEC. It was not possible to establish a threshold of ATP concentration or AEC below which internal disorder develop. In conclusion, poststorage quality of 'Rocha' pear was better at the extremely low pO2 of 0.5 kPa than at 3.0 kPa. 1-MCP was detrimental to internal disorders and blocked poststorage softening of 'Rocha' pear stored at 0.5 kPa O2.