Abstract
The factorial experiments were carried out and the gas mixture system was made to clarify the effects of O2 concentrations on Jonathan apples and to determine the optimum gas conditions of CA storage. Jonathan apples were stored in atmospheres of nitrogen with 0, 1, 3, 5, 10 and 21% oxygen at 4°C and 20°C for 63 days and 30 days, respectively. Carbon dioxide was excluded in every treatment.
1. The yellowing of the skin ground color was retarded in all oxygen concentrations at 4°C and in low oxygen concentrations at both temperatures. The skin red color changed purplish to brownish red in 0, 1 and 3% O2 at both temperatures.
2. No distinct differences were found in firmness and titratable acidity in oxygen treatments at 4°C. However, on holding for 7 days in air at 20°C after removal from 63 days storage at 4°C, fruits from 0 and 1% O2 were firmer and those from 21% O2 were less acid. At 20°C, the fruits from 0, 1, 3 and 5% O2 were firmer and more acid. The soluble solid was reduced in 0, 5, 10 and 21% O2.
3. The high ethanol content of flesh tissues was found only in 0% O2 at both temperatures, and after one month storage, the fruits of 0% O2 at 20°C accumulated about twice as much as at 4°C.
4. The critical oxygen concentrations for CO2 evolution rate were 1 and 3% O2 at both temperatures.
5. The fermented flavor was found in fruits from 0% O2 at both temperatures and 1% O2 at 20°C. The best edible quality was found in fruits from 1% O2 at 4°C, and 3 and 5% O2 at 20°C.
6. In the 2 months storage of Jonathan apples at 4°C, the optimum oxygen concentration for CA storage is 5%, at which the ripening is retarded without low oxygen injuries. More studies must be followed about the longer storage and with carbon dioxide.
