Abstract: We formerly reported a special lowoxygen CA combination (2 %O₂ + 7. 5 %CO₂) , which can control superficial scald of apples for a longer period after 4 months of treatment . Now , a further experiment of Starkrimson apples was conducted to study the effects of delayed and shortened treatment . The results showed that the scald incidence of apples of control (0 ℃, air) and conventional CA treatment (0 ℃, 3 %O₂ + 3 %CO₂) were 25. 6 % and 1. 02 % respectively , and their flesh firmness were 5. 79 and 6. 52 kg/ cm2 respectively after 123 days of storage. The apples of special CA treatment (10 ℃, 2 %O₂ + 7. 5 %CO₂) was scald2free after 123 days of storage , its flesh firmness (6. 63 kg/ cm²) was the same as that of conventional CA treatment and significantly higher than that of control . The apples of delayed treatment developed scald (6. 67 %) after 15 days of storage at 10 ℃in
air and 108 days of special CA treatment , its flesh firmness (4. 8 kg/ cm²) was significantly higher than those of control and conventional CA treatment . These results indicted that it is necessary to treat apples with special CA
combination on time. The scald incidence of apples of control , conventional CA treatment and special CA treatment were 46. 9 % , 36. 4 % and 0 respectively after 123 days of storage plus another 58 days of cold storage in air , their flesh firmness were 5. 28 , 5. 21 and 4. 5 kg/ cm² respectively. The apples of special CA treatment was also scald free after 96 days of storage plus another 50 days of cold storage in air , its flesh firmness was 4. 67 kg/ cm². Based on the consideration of both scald incidence and flesh firmness , it is possible to change the duration of special CA treatment from 4 months to 3. 3 months if we want to store apples for about 5 months. The formations ofα2farnesene and conjugated trienes in the peels of apple fruits were significantly inhibited by special CA treatment during CA storage.

Key words: Apples, Storage, Low oxygen controlled atmosphere, Fruit firmness, Superficial scald