COLD-INDUCED ACTIVATION OF 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID METABOLISM IN REWARMED GRANNY SMITH APPLES - CONSEQUENCES ON RIPENING

Changes in respiratory rate, 1-aminocyclopropane-1-carboxylic acid (ACC) metabolism and ripening in apples (Malus domestica Borkh. L., cultivar 'Granny Smith') were studied in relation to cold storage. Fruit were held at 4-degrees-C or 22-degrees-C for 31 days (4-degrees-C controls and 22-degrees-C controls, respectively) or at 4-degrees-C for periods of 2, 5 or 10 days before transfer to 22-degrees-C for the rest of the 31 day period. Ethylene and CO2 were produced at a low rate in 22-degrees-C controls. In 4-degrees-C controls, ACC levels increased greatly, showing an inhibition of both ethylene-forming enzyme (EFE) and malonyl transferase activities. In chilled fruit, ethylene, malonyl ACC (MACC) levels and EFE activity increased sharply after transfer to 22-degrees-C. These increases were accompanied by a significant rise in the respiratory rate, similar to an activation of a climacteric process. Chilled fruit also showed a loss of pulp firmness and acidity compared with fruit kept continuously at 22-degrees-C.