Varietal and Maturity Differences of Apples in Response to Ethylene in Controlled Atmosphere Storage1

Five cultivars of apples (Malus domestica Borkh.) each with 2 different harvest dates were stored in continuous flow controlled atmosphere (CA) at 3% O2 and 3% CO2 at 0°C or 3.3° for 3 to 7 months. Ethylene in the CA was maintained at 3 levels: low (mostly below 1 ppm, maximum 3.8 ppm), 10 ppm and 500 ppm. In comparison with low ethylene, 10 ppm and 500 ppm ethylene in CA did not significantly affect the soluble solids, titratable acids, firmness and sensory evaluated ripeness of ‘Delicious’, ‘Golden Delicious’, ‘Indared’ and ‘Cortland’ apples harvested on either date and of ‘McIntosh’ apples harvested after the onset of climacteric. However, ‘McIntosh’ harvested before the onset of climacteric retained higher acids, firmer texture and were sensory evaluated as less ripe when kept in CA with low ethylene than that with 10 or 500 ppm ethylene. ‘Delicious’ apples stored for 7 months in CA with 10 or 500 ppm ethylene developed severe scald but those in CA with low ethylene did not.